Hi everyone,

I'm having my yearly no start problem with what I assume is the ECU not sending power to activate the primer fuel pump? I've had this recurring problem for years. Before I would just run to pull a part and get a working ECU, and stock up on them when I can. I have four known good ECU, but none seem to be fixing my no start problem this time. Maybe they've gone bad as well? The 30+ year old ECU electrolytic capacitors might be the problem? I've been driving with a 12vdc+ jumper on fuse #4. Not a great solution.

All connectors are clean, fuses are new, fuse box clean. All engine diagnostics check out 100%.

Any ideas?

I really appreciate it! Thanks!
Jim

Your fuse 4 bypass to run the fuel pumps and allow you to start is consistent with a failed fuel pump relay. It's a very common issue, far more common than a failed ECU. There are further diagnosis you could attempt at the ECU connector and/or FP relay, but in your case I'd simply start by replacing the relay. If you're handy with a soldering iron you could attempt to re-flow the main solder joints in the relay to see if that helps -re-soldered relays make great spares to keep in you car kit.

The later LH 2.4 ECUs are considered very reliable. I'm surprised you've needed to replace them, especially multiple times. Have you been doing arc welding on the car? The original pink label LH 2.4 ECUs used in '89 and early '90 were well known to have fuel pump control issues, but most of those are long off the road.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

I replaced my original pink label ecu 20 years ago with a remanufactured white label ecu. It worked for many years, then I got the no start, no power to fuse 4 issue. Replacing the ecu has worked every time so far. I have replaced the fp relay once. I've tested this relay on the bench and it appears to be working ok. It activates strongly and the contacts are very clean, power out under current is good. I'll try replacing it. Any other ideas? Thanks

The FP relay remains your chief suspect in my mind, so do follow that thought to the end. If you tried reflowing the solder in the past then it's perhaps worth trying again. I've had re-soldering jobs only last a few years and need repeating.

Without wanting to get you too much ahead of that FP idea, if you're asking for other thoughts for your no start then I can suggest keeping in mind:

o Double check for signs of FP relay overheating. Carefully inspect the integrity of the FP relay socket for signs of poor contact such as socket deformity, loose/discoloured terminals -pull/wiggle wires from the rear of an empty socket. Also inspect the relay itself for signs of overheating or less than virgin looking solder joints inside.

o If everything is checking out then there is also the possibility of damaged wiring elswhere. Because you've taken the ECU connector off a number of times, carefully inspect for bent pins inside the connector. You of course know to probe at the sides of the connector with the shell off rather than into the socket itself when doing testing. Those pins are very fragile and easily bent. Weakened contacts can even become moisture and temperature sensitive. Shoot some spray contact cleaner and air into the connector while you're at it during inspection.

o I presume that in a quiet area you can't hear the pumps spin up for a second or so when the ignition is first switched on (KP-II). You often need to lean out of the car with the door open to hear the pump underneath or use an assistant. If you can hear the initial fuel pump spin up then the relay and ECU are not suspects (the CPS then becomes a prime suspect).

o You said it passed all diagnostics. I presume that just means there were no codes on either port 2 or 6. Did you run OBD DTM 3 as described in the 700/900 FAQ here https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm#FuelInjectionandIgnitionDiagnosticCodesi ? It tests the ability of the ECU to control system devices. If you can't hear/feel the injectors ticking and the IAC rocking then that widens the scope of your no start problem. DTM 2 is also fun to play with, but I don't see that it's relevant to your no start situation here beyond testing the CPS rpm sensor (it's not a conclusive test in any case).

--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Look at the two schematics that Jim sent me.
The two do not agree, and seem to be generic Chiltons or whatever.
The ECU schematic indicates both the in-tank and main pump
run on the same YR wire with an unidentified fuse (maybe F4) in series
to the tank pump. That's unlike Volvo to be so fuzzy.
Jim's fuse block diagram has the intank pump off F4 and the main pump off
F6 with a red wire.
Do you have genuine Volvo schematics for this car?

Thanks, Bill

Bill, here are the correct maps:





Well, they are the maps from the 1992 wiring diagram manual, but they don't correctly show the change in wire color that occurred that year. The orange wires at the AMM, IAC, and injectors were changed to red/black. Volvo's green books contain some copy/paste errors in the wiring diagram detail pages.

--
Art Benstein near Baltimore

You do not need a parachute to skydive. You only need a parachute to skydive twice.

Hi Art,

Thanks for the the right schematic. It's no fun using bogus schematics.

I see the AMM hung on the duel fuel relay.
Does Volvo provide circuit theory for the system?
What impact does the AMM output to ICU have, if any,
back at the fuel relay inputs from the ICU?

Nice job posting that stuff, what software are you using?

Best regards, Bill

“If you don’t read the newspaper, you’re uninformed.
If you read the newspaper, you’re misinformed.” -Mark Twain

Thanks Dave, BB, and Art!

I will follow these ideas and report back what I find tomorrow.

So far, it starts and runs great with 12vdc+ jumpered to fuse 4.

I ran the full diagnostic, all phases of 2 and 6, and everything checks out as being 100%.

I've cleaned all fuse box connections, cleaned all contacts in the connectors, under dash and under hood.

The car was completed in December 1991 so I assume was a mid year 92?


I really appreciate all the help and great ideas! I've had this 100% rust free Volvo for a long time, and hope to keep it going trouble free until I convert it to electric, many years from now. Lol.

To Bill and others,

You can find tons of valuable LH 2.4 info in the green Volvo Service Manual Section 2 (23): Fault tracing, Design, Repairs, Function, Maintenance for LH-Jetronic 2.4 fuel system Engine B230F 240 1989-19.., TP31361. It was published at the end of 1988 so there were a few minor revisions as things went along for things like wiring diagrams, but the principles and components remain the same. It's got extensive diagnostic procedures and proper documentation of the OBD system.

You can find a copy in the Oz Volvo Technical Archive https://ozvolvo.org/archive/ . In the filter field at the top type in the above TP number.

Additionally, there's an excellent table there with the LH 2.4 ECU connector pins and functions fully described. Type "Connector" in the filter field to find it.

Lots of other good stuff in the Oz Volvo archive. Well worth bookmarking. The archive is not Google indexed so doesn't pop up in searches.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Convert to electric? My father sent me an article describing a $28k (2015) conversion of a P1800 to plug-in with 75 mile range. You can do it! Or rather get it done.

Meanwhile, momentarily remove your jumper cheat and get a test light at Walmart and check the blue/green wire into the fuel injection relay (terminal 86/2) while cranking. Know how to do this back probing? You should see it go out (referenced to ground) to enable the pump portion of the FI relay. That's what fails in the pink label syndrome. I've never heard of this function failing in the white label (revised hybrid) ECUs. Which one are you running now? A white 561? A 951?
--
Art Benstein near Baltimore

A TV can insult your intelligence, but nothing rubs it in like a computer.

I didn't have a chance to check anything today except I know that all of the four ECU I have are white label 951, two are made in Germany and two made in Spain. I also have a ECU from a b234 16 valve turbo, but knew it wouldn't work. The two fuel pump relays are German and work when activated on the bench, but not in the car.

I'll do the other things tomorrow and report back. I really appreciate everyone's great ideas and help.

Hi Everyone!

I checked for ground at startup on the fuel pump connector 86/2. There's no ground connection through the ECU. There is ground connection through the ECU at 86/1 and that side of the relay activates.

Does this mean that section on the ECU is bad? Or possibly something else that connects to the ECU and sends a signal to make the ground connection to 86/2?

Ideas? I very much appreciate all of you guys!

FP relay 86/2 (ECU pin 20) will only see ground when the ECU is getting an rpm signal from the CPS (during cranking and running) and as well momentarily when the ignition is first switched on to spin up the pumps for a second or so to pressurize the system. Another pre-requisite of course is that the ECU has power on pin 35.

Your CPS is not overly suspect as you are able to run with fuse 4 jumpered, however there is always the remote chance the CPS signal is weak at cranking levels so don't totally discount it just yet while you're chasing a phantom problem. Also note the ECU gets it's rpm signal from the ignition module, not directly from the CPS.

Your chief suspects at the moment remain the fuel pump relay, ECU/FP relay wiring and the ECU itself.

Please follow the LH 2.4 green manual I referenced you to earlier. If you carefully follow the diagnostics at step D associated with fuel pump operation and related wiring you should be able to properly isolate your problem.

The main diagnostic step for you at this moment is to try grounding pin 20 at the ECU connector. If that allows you start then you know the problem is at the ECU connector or the ECU itself. For that test, best to use a thin gauge solid core wire where you strip back just enough (like 1/16" or so) to touch the side contact on the connector. To make life simpler and safer, I would recommend putting a bit of masking tape over the neighbouring contacts exposing only pin 20 so you don't have to count pins and risk making a mistake. I will often use a fine tipped felt pen to mark my pins of interest. With that ground being touched, if you then turn the ignition switch on (KP-II) you should momentarily hear the pumps run (or see momentary +12V at fuse #4). If not then try cranking. If the pumps do run then at that point you know it's likely the ECU or the ECU connector. If the pumps still don't run then you know it's the FP relay or wiring to it.

Please post back with your progress.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Have you heard of a faulty ECU coming up with no codes?
Maybe his OBD port has a missing ground, if he in fact got no codes?
I'm waiting to hear he got 1-1-1's on all ports.

Troubleshoot a possible dead OBD port.

Bill

ECUs can easily be faulty and not throw a DTC, in fact it's probably the norm.

The OP indicated he got no codes. Because the engine runs perfectly fine when fuse 4 is jumped, I wouldn't expect to see any codes, leastwise anything relating to the no start.

As for your OBD socket problem, it's not uncommon. I've never had it happen, but you should be able to find notes on it, possibly in the FAQ. As I recall, you may need to replace the main A socket. I vaguely recall there's an internal diode that can go.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

>The OP indicated he got no codes. Because the engine runs perfectly fine when

>fuse 4 is jumped, I wouldn't expect to see any codes, leastwise anything

>relating to the no start.

He needs to check for codes without his jumper hooked up and report back.

My OBD port just needs a new bullet connector on one pin where the
rubber thingy that holds the pin disintegrated.

Here's an off topic item of interest... where to post for comments?
https://www.npr.org/sections/money/2022/08/23/1118457271/someone-stole-my-truck-i-got-a-crash-course-on-the-wild-black-market-for-stolen-

Cheers, Bill

Hi Everyone,

Thanks for the great ideas!

I've checked for codes with and without the jumper and they all are 100%.

I'll do the other tests tomorrow and try to eliminate the good and bad.

If you have other ideas, please keep them coming! I've had this car forever, and still learning how it truly works. Like I didn't know that a weak cps signal could effect this part of this circuit. These facts are very important. Thanks!

Hi everyone,

I put the ground jumper to relay pin 86/2 and it started fine. So I assume my ECU isn't working? Ideas of a possible repair? I've gone over the board as best I could and don't see any cold solder joints or obvious problems.

Any ideas would be greatly appreciated. Thanks!

That certainly points the finger at the ECU not being able to control the fuel pump relay. I'd want to reconfirm that test at ECU connector pin 20 and as well inspect the connectors carefully just to make sure it's not wiring or contact pins.

Of all the stuff I've seen written about the -561 fuel pump control problem, the issue appears to be with the piggy back hybrid board. There is generally no visible circuit board damage, although on the one I had go bad there were signs of heat damage on the main board, near the outer edge, on the side opposite the edge connector as I vaguely recall. There were apparently two versions of hybrid board used, the first more problematic version was in the pink label ones, but was reportedly also used in some of the white label ones before they finally switched to the newer hybrid board and there have been suggestions that even the new hybrid board wasn't totally problem free (as you have now discovered). As noted on Bill Garland's ECU page, if you go for another ECU try to source a -933, -935 or -951 which are supposedly better substitutes. Double check that whatever version you use matches the EGR capability of your engine.

Here are links to a couple of pics I found on Art's website to aid in hybrid board identification:
http://cleanflametrap.com/561bad_lg.jpg
http://cleanflametrap.com/561good_lg.jpg

You seem to be eating more than your share of ECUs. You are perhaps a good candidate to consider using an aftermarket universal fuel pump controller to completely bypass this issue. It's designed to be operationally equivalent to the ECU, priming the pumps at startup and only running the pumps when the engine is actually turning over using a tach feed. It's made by Revolution Electronics and I see a few still available from them on Amazon, not grossly expensive at all. I have no first hand experience, but anything Dave Barton recommends is worth thinking about. It would save you trying to source a compatible ECU as they are getting harder to find after all these years plus being of unknown quality. At least you know yours can run the engine properly as long is it's getting fuel.

Start by reading about it here on Dave Barton's website
https://www.240turbo.com/fuelpumprelay.html#universalcontroller

Note that Dave recommends using that controller to indirectly operate a pump relay. You should be able to use a slightly re-wired version of your existing FP system relay.

There's a link in that article to the Revolution website product. There are installation instructions you can download. A Buy Now will take you to their Amazon listing where you can check out ratings, reviews and answered questions.
https://www.revolutionelectronics.com/Products/Fuel_Pump.html

I haven't thought this out in enough detail to know the best way to do it, but it looks pretty straightforward, especially in a 240. You'd want to connect your existing relay terminal 85 to the controller and 86/2 to ground, also severing the 87/1 to 85 wire at the connector. I'd have to think a little harder about the 86/1 side of the existing relay, but in your case ECU pin 21 is providing ground okay so you could leave that side asis if needed. You shouldn't need any new wires to the ignition switch or fuse panel, all the power you need should be at the existing FP system relay. The controller wouldn't be drawing much extra current to operate the existing relay. As you likely don't have a tach there should be a loose wire hanging for it behind the instrument cluster (White-Red I believe) rather than having to go all the way to the distributor.

Let us know what you think. I'd be especially interested in comments from anyone who's tried going this route.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Thanks Dave,

That's what I was thinking too. All the ECU I've had are 951. I currently have 4 and I guess they've all gone bad sitting on the shelf, but all are over 30 years old. That's why I was wondering if it might be the electrolytic capacitors on the board. These days it's rare to get 10 years out of them. The ones on our dryer board went out months after the warranty expired (of course). I soldered in new ones and it was good to go. Has anyone experienced this on the 240 ECU?

Thanks for the amazing help Dave, and Everyone. Please keep ideas coming, for now I'll look for an ECU.

Oh, what about the crank speed sensor effecting the ECU? Is there a way to test this? I have a good volt meter, but don't have an oscilloscope. Thanks

Re. Testing CPS functionality. You would need an oscilloscope and maybe the specs. In your case I wouldn't worry. Your engine starts and runs fine when it has fuel. There's an OBD test that can check basic functionality. There's also a basic ohm check you can do to try diagnosing a really bad one, but I never bother, simpler to just swap in a spare. The first signs of CPS failure are often a hot stall, a nostart soon after shutting the engine off or a hiccup/stall/nostart when the cable moves. Periodically inspect the CPS cable insulation for signs of damage, especially for splitting down near the sensor and for chafing behind the block where it can touch the water pump return line or oil filler tubes. Originally there are one or two swivel plastic standoff clips at the back of the block that keep the cable from flexing and chafing. The standoffs eventually break or go missing. You can try fashioning your own standoffs using looped zip ties and scraps of vinyl tubing, but they may not last long, especially if you use cheap quality ties.

Re. Old ECUs. Other than the -561s, our Bosch LH ECUs have a general reputation for being well built and long lived. Many of us are happily running on 30+ year old ECUs without worrying about them. In general, electrolytic capacitors should degrade more through use and operational temperature than age sitting on the shelf. Bosch will hopefully have used higher quality caps, less likely to leak, spec'd high enough and with a tighter tolerance for a more consistent ESR decay less likely to affect operation over time and usage. Many appliance control boards have a whole different reputation, as you well know. We're fortunate to have at least some supply of used ECUs for our Bricks, whereas for appliances the lack of availability or cost of a new board easily makes it a writeoff.

Did that universal fuel pump controller idea appeal to you? It would sure be my approach if I couldn't easily lay my hands on a good used ECU for less money. Your -951s on the shelf would likely then become useful spares.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

The universal fuel pump controller is a good idea, I was hoping to be able to repair the ECUs I have if possible. It's interesting that I have four 951 that all worked fine when I bought them. They've been sitting on a shelf and now none of them work. It seems my problem might really be elsewhere? Something that controls the ECU? Especially since the 951 are know to be reliable. What are the odds all four of mine have gone bad while sitting unused? And this problem I've been having has been going on for many years. I suppose I should try a CPS to rule that out before I get into configuring a universal fuel pump controller?

I very much appreciate your great ideas. Thanks

Hi

I have been reading the newspaper about this and as a subscriber, writing an editorial is kind of useless with so many good opinions already given on this subject.
These fellows on here, like as so many others, are more experienced in this stuff too.

I was going along with the fuel pump system relay as it being a known as a proven “bad” guy. Then along comes the pumps with their tricks of the trade. (:(

I’m with you on the four ECUs going bad on the shelf is as unlikely as having four meteorites or lightning strikes hit the same spots. Let alone it being your garage in the same day. Must be something with the car instead.

The CPS has had its quirks but the paraphernalia that associated with needing to read the correct and exact signals from it, makes it even more complicated. If units get a garbled wave or thinks is it’s slightly mutated it’s liable to stick it hand up and go nope not today comrades!
This appears as an overlooked area during the designing and testing phases of all of the systems working together. Throw in some age and who knows what is lurking in the bushes.
There’s good or bad but ugly, as it is right in between some thick green grime.

If not for the CPS’s signal weirdness, then the only other guy is the ICU itself.
It has the responsibility of being in between the two electronic champs.
Of course, then there are those wiring guys who play with it too.
To them signals are signals and when it comes to wiring costs an inch more seems to be big money.

Luckily we can see into that stuff on the ends anyways.
If they could put smoke in a tube we, would be using some puffs for signals.
Light optics and glass fibers plus computer coding is getting us there! CANBUS here we go along with the mysteries and more test instruments. BETTER …. For whom?

Can you check the ICU’s outputs? How many can there be? Coil and ECU. A tachometer or rpm status for the loading programs? Lately that’s for transmissions too and Luckily, not ours.

Not much has ever been written on ICUs.
Once there was one and it was overheating, over there in Malaysia.
That was found malfunctioning by a person putting on a 12v computer fan onto it.
Supposedly it stopped acting up and so it caused the posting of a thread I read.
Maybe Aramin knows more?
He might know who it was or was it his car?
He is like Art Benstein … who gets into necropsy and investigates things. A real good reporter of news worthy stuff for us!
Lots of knowledge gets gained with those kinds of curiosity habits.

I know it’s under the dash and it is still like shooting in the dark.
Do you have one a ICU laying around?
They are right near the ECUs on later cars, not under the hood now.

It’s easier to get to than that CPS but then again we know that how it is mechanically to play cards too? (:)
I’m Sure watching the thread.

Phil

Hi Phil. Because the OP can start easily and run normally once the fuel pumps are running then it's difficult to imagine a missing CPS signal to the EZ ignition control module or a missing rpm signal between it and the ECU. The injectors wouldn't happen. My mention of a weak CPS signal was grasping at straws in case the OP hadn't fully described the symptoms or later noted occasional normal starting.

If the ECU is missing its rpm signal from the ICU then that triggers a Check Engine light with a DTC of 1-3-1 on port 2, but this only seems to happen if the signal path is lost between the ICU and ECU, such as a broken wire, not a missing pulse. Similarly, if the ICU is a missing the rpm signal from the CPS then a Check Engine happens with a DTC of 2-1-4 on port 6, but again this only seems to happen when there's a missing signal path, such as a broken sensor or sensor cable to the ignition module, not failure to produce a pulse. Seems kind of dumb, like it would need to have an rpm signal from some other source to know for sure the crank is actually turning to be certain that a CPS pulse is missing. It obviously doesn't trust the starter solenoid.

There is one way to test for an rpm pulse during cranking and that's using OBD DTM 2, although the documentation of that step of the test in the FAQ is less than perfect. Refer instead to the OBD section of the Volvo LH Manual noted elsewhere in this thread. As I tried to note, it's seemingly not a foolproof test of the CPS. The test doesn't seem to care about pulse timing, waveform quality or number of pulses per revolution. All it seems to care about is seeing a certain number of pulses, let's say 4 recognizable leading edges, no matter how many actual revolutions, before ending the test and flashing the 3-3-1 success code. It's not a perfect test, but it's a test many of us fail to do when chasing a no start or stall.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Thanks for acknowledging my points of thoughts and a very thoughtful response that we all are thinking along the same lines.
Your points on the CPS dies have it limits of conjecture to get blamed for and believed, if all of a sudden performance changes.

Art has noted for us of what not to do to pin 20 on the ECUs.
That pin is like a puffy bister that you don’t want to go poking around with, but you cannot help yourself from thinking about it, because it’s there. (:)
That pin or the whole connector harness, has a lot of things to do every time it gets taken on and off an ECU.
I want to be suspicious of all of those clips right off the top.
I’m not familiar with how the ICU gets to talk back and forth either but ….?
I have not been under there much to do anything.
Maybe once in twenty years to exercise the clips out of curiosity and give it a very light spray of LPS to make me feel good.
But then, I do not have the weather environments that other cars have to endure either.

It’s been my experience that most of the time a failure or fixes are caused by human interventions.
He has tested each ECU unit on the car or cars so maybe something has had enough of that!

He said he has bypassed the ground in the harness and the pumps run so yes everything else is working.
So for me, that’s a big arrow pointing at a harness communication issue and from my experiences that the grounds seem to be more than half of every circuit.
I say this because, there is one connection at both ends, so it covers two or more places to look.
Arts pictures of that one splice is a good example of more than half a circuit. Especially, if it’s making and breaking or broke even.
Totally broken connections makes for a nicer troubleshooting or hunting expedition.

I agree with your assessment of OBD.
I can see why OBDs can and will continue to have “its openings” and not “short” comings, to be fallible.
The sophistication of them has moved a longs ways but in so many ways the variations have raised such a havoc with keeping up with maintenance costs and those check engine light fears, that it can take the pleasure of driving, out behind the proverbial wood shed!

I’m worried about where are electric cars are going and if they will keep it simpler and down to earth for us laypersons.
Ownership of anything is getting to be very ominous.
I see “call-a-car” or more of let’s say, “toss back” vehicles on the horizon.
Throwing it “away” is not as far as it used to be? (:-) no more wrapping it up newspaper like the old days.
Besides newspapers and those advertising methods are endangered like our post offices.

I read long long ago. Maybe 40+ years, that 2023 was “studied” to bring on “a change.”
Nothing was really defined.
So with that, I wrote the article off, but remembered it, as I saw it as “that is always happening.”
Well, We might be a little ahead of that schedule.

Thanks for including me in the thread more.
Phil

Trying to identify your no start fuel pump control problem at the ECU board level strikes me as a futile exercise. In the 25 years I've been following this forum I don't recall anyone here making a successful repair. If it was something as simple as bad solder points the word would be out by now. Unless you are intimate with the board design and electronics I can't imagine you will accomplish anything other than the satisfaction you tried and failed. That's as far as I managed to get when my '89 LH 2.4 board went bad on my 16-valve 740. It was one month past warranty and there was no such thing as used board availability as LH 2.4 was brand new at the time. There was no such thing as eBay, I had to buy a new one from the dealer($$$).

Trying another CPS would not be the worst idea as they are often associated with mystery no starts, however it wouldn't be on my suspect list based on what you've said so far. If simply grounding fuel pump terminal 86/2 (ECU pin 20) consistently allows you to now start then the CPS isn't your issue. The finger points solidly at the ECU itself or wiring to it associated with fuel pump control.

If the -951s you have as spares were known to be good then the odds of them failing sitting on the shelf are slim to none. If this has been an on-going problem over multiple ECUs then something else must be happening. Going with a universal fuel pump controller will bypass your problem, but still leaves the question of precisely where the failure is.

Based on the evidence so far, if it's not multiple ECUs similarly failing (and because it's unlikely to be sensors like the CPS if you can otherwise run normally) then one reasonable explanation is bad electrical connections.

Like I said, re-test at connector pin 20 and carefully inspect the ECU connector and the wiring to it as well as the relay socket.

In giving this more thought here, one distinct possibility that could easily keep affecting multiple ECUs is a bad ground connection for the ECU. Bad grounds are good for all kinds of mysterious and periodically intermittent behaviour. The LH 2.4 ECU uses multiple ground pins. It's quite possible one of those ground pins is dedicated to the fuel pump control section of the board, especially something like the one that serves the piggy back hybrid board that we know is associated with fuel pump control. You could try examining the board to spot the likely ground path on the hybrid board and follow it out to the edge connector, but it's probably simpler to just check the integrity of all the grounds at the ECU connector.

Using an ohmmeter test probe into the side of the disconnected ECU connector (remove the connector shell to access the side contact area), carefully measure resistance in reference to a clean bare metal chassis point of all grounds. You want to check ground continuity on pins 17, 19 and 29. Pin 19 would perhaps be the most likely candidate as it's the board neighbour of pin 20 associated with the hybrid board.

Now if I recall correctly from Art, the ECU chassis ground attachment point for 240s is a screw on the intake manifold (on 700/900s there is ground rail behind the ECU). I'm not sure if these go through a connector block (which would make pin contact in the connector a suspect area) or it's a direct wire. The green book 240 Volvo wiring diagrams I have access to don't show the connectors and ground points. Defininitely open up that ground connection, clean and remake the grounds.

Good luck and please report back.

--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

We were typing at the same time, I guess.



This shows how the fuel injection system gets its ground references. ECU-17 is the power ground, and the reference for the relay driver transistor on the hybrid.



To see the actual wire you'd need to follow it back under the vinyl sleeving where the splices are made. Folks have reported corrosion problems with the splice, but I doubt a poor ground is to blame in this thread about 951's being killed.

One other cause I remember learning was a mechanic who was newly enamored with a "power probe" which in knowledgeable hands can be a useful diagnostic tool for energizing circuits. I emphasize knowledgeable because if such a tool applied 12V to pin 20 on the ECU, it wouldn't matter what else was wrong, the part on the hybrid would be destroyed. I'm familiar with hybrid microcircuits, especially from this era, and there is no field repair of them I'd trust in a car.

--
Art Benstein near Baltimore

Wise men speak because they have something to say; fools, because they have to say something -Plato

Glad you could post the ground connection locations, Art. I knew there'd be more than one spot. Yes, we were obviously composing our replies at the same time. I haven't had my head under a LH 2.4 240 hood for a couple of years so any ground connections are a vague memory at best. I didn't realize until just now how much you've been into -561 ECU problems. I bow to your expertise in such matters.

Your thought of spurious voltage from a line tester frying circuits is right up there with me asking if anyone has been using an arc welder. Another thing Volvo cautions about in the LH manual is baking high heat in body shop ovens.

Your shorted relay coil theory is an interesting thought, especially about being able to consistently take out working ECUs. Makes you wonder how many bad ECUs might have had a longer life, first replacing the serial killer FP relay as the most likely cause and when that didn't fix it then resorting to replacing the ECU, with everything now back to normal. I absolutely agree with trying another relay to get the existing FP relay out of the equation, most especially if a new ECU is being tried. The OP's noted bench testing of the relay would hopefully have turned up such a flaw as a shorted coil, but not necessarily if only one side of the relay is being tested. After jumping fuse 4 and getting it running, first thing I'd have done is swap in another relay before doing any further testing or at least re-flowing the solder simply on spec as it's such a common cause.

This is indeed a more involved problem than we normally see here and with suggestions of multiple ECU failures right from the start had me cracking open the manual and doing supplemental reading to more carefully consider the possibilities.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

I've arc welded on 240's without knowing or thinking beyond what I was taught in the early 70's. That is, disconnect the battery and apply the welder's ground as directly as possible to the member being welded. I think the idea in those days was to avoid the current travelling through bearings and gears.

Do you know if that procedure is safe enough on electronic cars, or should other things be disconnected ? I haven't fried anything that I know of, but ignorance is bliss.

Peter

If you do a bit of reading the general guidance is to disconnect battery negative ground. Many don't seem to bother. There is some anecdotal reporting of sensitive auto electronics being taken out even with the ground disconnected when arc welding nearby. Our ECUs are fairly well shielded in their metal casing, so likely of less concern in that regard. I think it's mostly a case of better safe than sorry.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

"The OP's noted bench testing of the relay would hopefully have turned up such a flaw as a shorted coil..."

No hope there, Dave. If the shorted coil turns could be discovered by testing on the bench, it wouldn't be intermittent, it would be solid, and that relay would not have worked in the car.

"This is indeed a more involved problem than we normally see here..."

Yep. Kinda wish you could be there to have a look yourself, right?

--
Art Benstein near Baltimore

"To do is to be." - Descartes
"To be is to do." - Sartre
"Do be do be do." - Sinatra

Hi everyone,

I didn't intend to have such a difficult problem but there it is. How many millions of these amazing 240s were built? I suppose statistically it was bound to happen after these years?

Thanks for the great conversation and ideas. For now I bought another white label 951 from a verified 120k 91. I also bought a new relay just to be sure. I can report that everything starts and runs exactly like it should.

Before I installed them, I went back through every connector and ground connection, even ones that don't directly go to the ECU. I cleaned them with deoxit and contact grease and tested the connections with a vm where I could.

I guess I'll go with this for now since I need to use the car. Please keep the discussion going and I'll consider everything because I don't want to be here again in a year or two.

Thanks so much to everyone for the great info and lessons on how the 240 actually work, the things most manuals never even touch on.

Glad you've got it working with a replacement ECU, new FP relay and cleaned up grounds. Hopefully that's the end of your issue.

The mystery remains as to the origin of the problem and why multiple ECUs either suffered a partially fatal blow of stray voltage or otherwise couldn't provide ground on pin 20. You've got a bunch of us quite curious.

The FP relay you were using was of course common to all the cases so is highly suspect.

I'd have been interested to eliminate the possibility of it being related to a bad ground after you'd cleaned up all the ground connections by simply trying your existing ECU and as a follow-up test trying the new FP relay before swapping in the new ECU. It is so rare for multiple ECUs to fail. If you're ever in that rats nest of wiring again, maybe swap in the last ECU just to see if it now happens to work.

The similar recent thread that Art referenced over in the turbobricks forum with a 1990 240 is interesting. Some of the discussion in that thread about relay operation and fuses is misleading and doesn't accurately reflect LH 2.4 compound system relays (no such thing as an auxiliary air valve in LH systems -that was CIS used with K-Jet/D-Jet). The OP there neglected to identify his was LH 2.4 ('89-on 240 was LH 2.4 in the North American market except '91-on 240 with manual trans was LH 3.1) It would seem in that case there's a good chance the ECU got taken out by some other errant voltage source rather than a psycho fuel pump relay with scrambled brains.

I've been doing some general googling on fuel pump control issues in all makes where a bad relay might have affected an ECU, hoping it might suggest others have found relays with manufacturing problems that might take out an ECU, especially multiple ECUs. I can find a number of similar problems of a missing ECU ground, but so far I haven't found one where the relay itself was pinpointed as the cause. One reason for that may be that people would assume the FP relay was at fault and replace it without doing a full diagnosis and only then realize the ECU was also bad, especially as ECUs can be so expensive and difficult to come by.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Dave and Art,

I didn't want to risk blowing the 951 I had just bought with my old fp relay, so that's why I swapped it before installing. But the old relay worked fine on the bench and installed in the car with a ground jumper connected.

I'm not sure what the problem was, wish I did. Honestly, every connector, connection looked fresh, shiny and new, but I cleaned anyway since transparent oil films can deposit from the plastics/vinyls outgassing for 30 years.

All in all, I haven't really solved anything. I just replaced the ECU like I do every year or two, and have been for 10+ years. Other than the fp relay pin 20, everything works fine on the old ecu, but unless they're retrofitted with added timers, etc. they're no good really. It's easier for me to buy one than to retrofit. I figure by the time the used supply dwindles, we'll all have 1000hp electric motors in our 240s. I'm sure that if Ingvar Kamprad were still alive, he'd have converted his 91 240 to electric by now. lol. I welcome our electric future when its affordable.

Much thanks and gratefulness to everyone who contributed ideas and thoughts to my problem. Take care, and I'll contribute to discussions if I can.

"Please keep the discussion going and I'll consider everything because I don't want to be here again in a year or two. "

I'm beginning to wonder if you have company in this yet unexplained destroyer of 951s. Check in on this thread just popped up: http://forums.turbobricks.com/showthread.php?t=365375

Another thought I had about fuel relays. I wonder how many aftermarket replacements and even incorrect units have the six-spade configuration to easily plug in that spot, either with defects that could run 12V directly to the ECU pin 20, or because of another application, be wired that way. Could be a serial killer lurking in the auto parts world.
--
Art Benstein near Baltimore

Life is like a roll of toilet paper.
The closer you get to the end the faster it goes.

"I'm beginning to wonder if you have company in this yet unexplained destroyer of 951s. Check in on this thread just popped up: http://forums.turbobricks.com/showthread.php?t=365375 "

Turns out the issue in this thread was a pink label 561, not a 951, so Jim, your car is still seemingly the lone target of this 951 serial killer.
--
Art Benstein near Baltimore

“Dance like no one is watching; email like it may one day be read aloud in a deposition.”

In nearly 20 years of monitoring the forums with a special interest in this failure of the fuel pump driver transistor, I've never had a single such failure with the white label 561, nor of course any 9xx ECUs. Nor have I seen one documented until yours. Nor has any white-label LH2.4 ECU been shown to have the failure prone hybrid the pink-label units had.

Having 4 failures, you have to acknowledge this failure has an external cause. It has nothing whatever to do with your crank sensor, and nothing whatever to do with capacitor aging. The only thing which could be a serial killer of 951 ECUs with this symptom (grounding pin 20 allows full functionality) is a direct short to battery supply. This would cause instant failure to any open-collector relay driver; even in the rugged new hybrid.

If you can guess one particular fuel relay spans all the failures, you might have one with an intermittent short of the coil winding. This is easy to imagine, because the start and finish of the fine-wire winding have only a thin coating of enamel separating them.



Go ahead and use a workaround such as a universal pump controller, or simply wire in a kjet relay as Dave Barton has done in the past, but if you invest in another 951, please look over the wiring carefully for anything that could cause a short pin 20 to battery, and please use a different example fuel relay from any you've had spanning the multiple failures.
--
Art Benstein near Baltimore

Some ancient threads from before we KNEW the white labels identified the later hybrid version. Back then it was only a shaky deduction.

http://www.brickboard.com/RWD/index.htm?id=721162
http://www.brickboard.com/RWD/index.htm?id=990665
http://www.brickboard.com/RWD/index.htm?id=734849

Excellent post Dave!

The fuel pump controller is an excellent workaround idea especially when paired with Barton's ideas for use with a relay.

I've been trying to resurrect an '89 Alfa Romeo Spider (running L-Jet) that has been sitting for about 6 years but the fuel pump relay has been a headache. It's a 7-pin Bosch job that is NLA. There's a couple replacement numbers but getting ones hands on them is proving difficult. I have one coming from...somewhere in eastern Europe...for the paltry sum of $74. --That controller may be a better solution in the long run.

I've already used Art's page to choose a good main fuel pump. I'll leverage his and the rest of the Volvo community's knowledge any chance I get.

The Alfa community is active, which is great, but much different than ours here. There's a lack of true technical information on the inner workings and home workshop fixes, replaced by directing people to a few suppliers/mechanics out to make a buck. It makes sense, there's a market and some parts are unique and scarce.

Thanks and have a great day!

-Will
--
XC60 / Odyssey

1-what number relay do you need?

2-worldpac lists the 69-218 bosch pump for replacement. i'd do that before subbing some other number.

Hi Chuck! Thanks for showing an interest. I don’t have a worldpac account to look things up, is it something worth doing?

2) I ended up with a Bosch 69-412. For the in-tank pump I purchased an Airtex per http://cleanflametrap.com/transferPump.htm. The -412 looks identical and seems to be doing the trick. Haven’t had to install the in-tank yet though I will eventually. The fuel lines on Alfas are notorious for rotting from the inside and all indications point to this car being no exception.

1) I gathered all the below part numbers for that big bugger of a relay. As best I can figure the only one actually available to buy is the HuCo, though no retailer in the USA has them for sale. I do have an order placed for the Herth+Buss via “Amazon Global Store UK”, but it’s been a couple months now with no indication that the order will actually go through.

BOSCH 0280230001
HuCo / Hitachi 132019
Herth+Buss ELPARTS 75614186
Hella 4RP008189141
STANDARD MOTOR PRODUCTS RY489
INTERMOTOR 59176
VEMO V20710001

ALFA ROMEO 605228760
ALFA ROMEO 116851104300
BMW 13631276264
FIAT 60522876
RENAULT 7700708960
--
XC60 / Odyssey

https://www.pelicanparts.com/More_Info/13631276264.htm?pn=13-63-1-276-264-M400

not affiliated with this place, just an example of brand and part number.

worldpac is wholesale only, needs business license and tax numbers along with credit report. no diys.

Amazing. I checked Pelican Parts, but only found the KAE brand part (which the Alfa folks say doesn't stop the pumps from running when the car stalls).

Thank you for the tip!

-Will
--
XC60 / Odyssey

Service the ground wires, especially at the intake manifold
and for the controllers, etc.
Check your OBD ports for codes again.
Make sure you get a 1-1-1 on each port.
That should give a health report for the ECU and any missing signals, etc.

The LH manual that Dave suggested is first class, did you check it out?

I have a failed bullet connector at one of my OBD ports
so I can't read all of them now.
I'll get around to fix it when I recover from my
shoulder replacement. No rush, my car's running fine.

Good luck, Bill

The 1985 240 gets power at fuse 4 via the ignition switch.
Find the volvo wiring diagram for the 1992 240 to be sure.
Post back with the download link, if you get lucky.

Bill

Hi B.B.

Thanks for the fast response. Here are the diagrams. The signal from pin 20 and 21 are what activate the fuel pump relay (Y-R on diagram), through fuse #4. I have no voltage on 20 or 21.

I guess all four of my previously working and stored on a shelf ECU, are all now bad? Could it be something else?

ECU pin 20 and 21 do not get voltage from the ECU. The ECU ties them to ground when it wants to energize the FP system relay. You will not see voltage on those pins if the FP relay is toast as I suggest is most likely. If the ignition switch was the problem you would likely need more than a fuse 4 bypass to run, but it remains a possibility. Please refer to my earlier post.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Hi Dave,

Ok, I understand the ecu pins now. I'll check the relay again. I really appreciate your help.

https://i.postimg.cc/Y2XH6jNN/Volvo-LH2-4-ECU-diagram.jpg

https://i.postimg.cc/y6f2t5b0/volvo-240-fuse-box-diagram-1992.jpg