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Just when I thought my 940T was behaving, it started gagging,
tending to stall, no power and reminding me about Murphy's Law, and
suddenly the joke's on me again.
I took it for a spin with a 0-50 amp analog ammeter plugged into Fuse 1 socket
in place of the fuse. (Main fuel system fuse)
(The HF current tester has a 30 second limit, so is unsuitable here)
The car cooperated by running terrible, and doing it's best to stall, and had
severely decreased power, having to nurse extra gas peddle to avoid stalling.
Fuse 1 ran at 10 amps stable the same as when the car is happy,
suggesting that the fuel pumps are behaving. There's a new RSR.
Now I searched through the sorry library I have for LH 2.4 and EZ117K
and found these interesting items:
* RPM & crank position info from EZK is needed to enable the fuel system.
* Governor Function: EZK module uses the power stage to interrupt every other
plug, Usually becoming active at 6200 RPM.
So I replaced the CPS, and instant relief.
After a few hiccups when starting, the engine smoothed out and ran fine.
The old OEM CPS looks fine and I can see no sign of harness failure.
I get 179.5 ohms gradually increasing to 180.3 on the coil and the third is a ground. I see no high resistance short to ground wiggling the harness.
Is poor performance for after market CPS's due to cheap harness wire and crappy shielding? The replacement is a cheap Chinese Karpal CPS.
Why did this CPS fail? Isn't it a simple induction coil, either good or open?
This problem started suddenly as if someone pulled a switch.
Could the problem have been the CPS connector? I used a little dielectric silicone on reassembly.
Do the EZK and LH.4 module connectors need periodic service?
What's with the Governor function? can that decide to kick in without high
RPM? Is that the "limp home mode" where every other plug fires?
Is there an updated LH2.4 and EZK Ignition manual for the 940?
Comments encouraged,
Bill
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Bill, the EZ-117K Ignition System diagram you have posted is functional, whereas (label 217) is the ECU in the footwell on the passenger side behind the kick panel. The EZ-117K module (label 260) is on the driver's side and up...you need to remove the bolster panel, remove and look up and to the right of center...there it sits in a cradle (with a pink or blue label) to the left is another module which is the ABS module. I suggest not to overthink the situation at hand, changing the CPS is prudent and not too expensive, BUT I support using either Bosch or an OEM Bougicord. The failure of the CPS is common, time and wear predictable, I use the Bougicord and ALWAYS carry a NEW extra with me. The idea of a governor is a rabbit hole I will step back from at this time.
I will impress upon you to learn about the resistor pack (they rust, impeding current) that powers the injectors located on the inside of the engine compartment driver's side near the ignition module (label 419) that are also prone to wear out or cause a fuss from heat, vibration and if the thermal paste dries out between the aluminum base (heat sink) and the ignition module causing intermittent bad behavior. There is more, but I will step back and give you time to think, look, find and ponder.
No Saws All needed.
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Hi Paul,
Thanks for chiming in with your comments.
The EZ-117K diagram is from the 89 700 ignition book and doesn't show
the CPS, and has the old Hall Effect distributor.
When you say "bolster panel" do you mean the panel under the steering wheel?
Does that mean I can't get at the ignition module from the instrument cluster
opening?
I like working under dashes as much as getting a root canal.
Best regards, Bill
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Hi Bill,
Its possible that you have a faulty EZK module (black plastic box). Not LH module (metal box)
As usual, the culprit was dried capacitors from old age
I had similar symptoms earlier this year. I checked the capacitors with capacitance meter and confirmed it. Replaced the parts and all was well again.
Anyway DIY repair not recommended for those with beginner's soldering skill. The copper tracks on the double-sided EZK board could delaminate with excess heat
So its easier to replace the module with known good part, lots of it available at eBay
Look for the exact part number when shopping at eBay
NB:
1. Only do this after you've ensured other ignition parts are working well
2. There is no updated EZK manual that I know. EZK is hardware based module. As the hardware remains the same there's nothing new to write about.
Amarin
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Hi Amarin,
Please elaborate on the exact symptoms you had with the EZK module.
Was the engine running on two cylinders with the failure?
How many caps did you replace? Do you have more particulars, photos?
Does the EZK unit come apart easily to get at the board?
No problem soldering here.
The problem will be finding the right caps.
Some caps are junk when new.
I suppose it would be a good idea to survey the LH module too.
Capacitors crap out with age.
Best regards, Bill
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Symptoms were:
1. Car started easily no problem there
2. Also idled well no shaking there
3. Problem arise when you press the gas pedal engine started to shake with loss of power
You're too fixed with the 2-cylinder idea ever since you read the manual. The 2-cylinder idea is for rev-limiting function at high rpm. No, these symptoms happened at low rpm above idle. Shakes like random misfire with loss of power.
I replaced 3 caps there. I never had new junk caps as I got my supply from farnell. Unless you get your parts from suppliers with lazy old inventory then yes you might get those crappy caps. The caps I'm referring to is beyond your usual neighbourhood variety. I had to search for old datasheets of the original caps (Philips) then match it with datasheets of new caps. You need long life electrolytic caps with moderate ESR just like the originals in EZK box. Otherwise the new caps might interfere/clash with voltage regulator's function.
Yes the shakes could be from other faulty ignition components too. I did mention checking the others first before suspecting the EZK.
Just get the eBay item. Its plug n play. No overthinking required.
Amarin
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Hi Amarin,
Do you have an amateur radio call sign?
How long ago did you rehab the ignition module?
Have you looked at the Fuel module?
What specific caps did you select for the swapout?
I'd like to order them, and do this job only once since
I don't have full use of my left arm after
torn triceps surgery and a full shoulder replacement.
I'm only part way through rehab.
Regards, Bill
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Hi Bill,
Do you have an amateur radio call sign?
-> No. I don't do amateur radio.
How long ago did you rehab the ignition module?
-> Feb 2022
Have you looked at the Fuel module?
-> Yes in 2019 pre-covid. Replaced those caps already
What specific caps did you select for the swapout?
->Vishay 105C 100uF 40v (2 pieces), Panasonic 125C 470uF 10v, Kemet tantalums 100uF 10v and 10uF 16v. These are for my non-turbo EZK. The Philips caps are obsolete now (25 years had passed). Anyway you need to open your EZK box to know what specific caps needed. Yours might be different for turbo EZK
I'd like to order them, and do this job only once since I don't have full use of my left arm..
->Thats why I recommend you to get a good working unit from eBay, save all the troubles (don't you agree?)
Amarin
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Hi Amarin,
Thanks for those details.
Tomorrow the rain will be gone and I'll try to access the module
and at least find out what the part # is.
Good for you to rehab both modules, you are blazing a path for geriatric
controlller servicing.
->Thats why I recommend you to get a good working unit from eBay, save all the troubles (don't you agree?)
Save what troubles? My Volvo is more than a car, its a hobby.
Maybe I'll need to find some Ebay controllers,
but I'd put new caps in them before I installed them.
Thirty year old electrolytic caps are time bombs.
You never said how badly the old caps were out of tolerance?
Best regards, Bill
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Hi Amarin,
I missed your reply until now.
Thanks for the details, photos, and comments.
Plated through holes are indeed a common failure point on circuit boards and
the worst offenders are under LSI's, no fun to remove to get at the repair.
I found two bad intermittent through holes in my 940 instrument cluster,
and was hard to confirm but easy to fix with a 1" jumper.
This was for the fuel gauge that was busted from day one.
It's a mystery how any through hole connections work reliably with that flex board.
I'm unable to work under the dash yet with with a lame left arm.
Luckily the car is running in it's perfect behavior mode now,
subject to change without notice, conforming to Murphy's Law.
If the engine reverts into "speed limiting" behavior, by seemingly
running on two cylinders, plan A is to unhook the battery for ten minutes
and see if that might reset the ECU.
There's a crazy idea promoted by Micro$oft.
Is there a a procedure to clear ECU memory?
Yes, I suspect the ECU is the likely culprit.
Best regards, Bill
USER ERROR: replace user and press any key
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Hi Bill,
Is there a a procedure to clear ECU memory?
->Yes. Disconnect the battery or pull out fuse #1 for a while. I usually do it about few mins.
Luckily the car is running in it's perfect behavior mode now,
subject to change without notice, conforming to Murphy's Law
-> Need to catch this troublesome fellow Murphy and put him behind bars!
(just kidding)
Good luck!
Amarin
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Hi Amarin,
I can't see how pulling fuse 1 can clear ECU memory.
Disconnecting the battery for ten minutes sounds more like it.
Maybe there's some ECU pin to short to ground?
Perhaps that info is buried in Volvo service literature, maybe airbag service?
Murphy lives everywhere, in every machine, is immortal, and has
"Get out of jail free" cards. Sorry to reveal the grim reality.
I'm kidding too, (about any humor in this)
The good news is: we remain optimists.
Eventually I'll report back with any findings.
Cheers, Bill
Doctor to patient: "I've got good news, and I've got bad news."
"What's the bad news?"
"I had to amputate both of your feet."
"What's the good news?"
"The man in the next bed wants to buy your shoes."
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Ahoy Amarin,
I see the LH module is on the passenger side wall
and the ignition module in the center with a harness going in the side.
This is what's high on the engine firewall with no connector that I see.
Is this the EZK module with the connector on the back instead of the side
as shown in the 94 pictoral ?
These are listed as "oscillation dampers" on one site?
Thanks, Bill
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Hi Bill,
The EZK module is inside the cabin compartment of the car, under the dashboard
For my car (right hand drive version) its beside the steering column (but first, need to take down the "above knee cover" inside footwell)
For your car (left hand drive version) I'm not sure whether its on driver's side or front passenger's side. Take down the "above knee cover" inside both footwells to look for it
No you can't take the module out thru the speedometer cluster. Need to approach from below, from within the footwell and looking upwards
Amarin
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That is a vibration damper on the fire wall.
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A vibration damper? What's that about?
It was plastic, it was rectangular, but it doesn't have a 25 pin connector.
I got 2 out of three, for zero points.
Now my second guess is that the ignition module is hidden under the windshield, in back of the radio, and you access by either Sawzall'ing the dash open or pulling the instrument cluster out to find it.
Here's the EZ-117K info that includes item 293, "Idle compensation relay"
that I don't see in the 94 940 book.
The location pictoral is a little fuzzy for the ignition module for a 940
newbie like me.
Maybe every so many timing belts, or decades, you gotta swap out old caps from the controllers?
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Your EZ-K ignition module (in LHD) lives up high on the right side of the pedal assembly. You will need to remove both the footwell and under dash panels as well as the knee bolster plate for proper access. Fairly easy to get at with good lighting, but the mounting bracket can be a bit of a knuckle scraper if you're not careful. I'll sometimes need to remove it when working on the later style square brake switches at the pedal that can be a real pain to remove without breaking the plastic tabs.
That black box thingy on the firewall is a vibration dampener, just a chunk of metal, as others mention. I wondered about it for years, especially with it having a braided ground strap. It's seemingly some kind of design afterthought to deal with harmonic vibrations that showed up at the firewall. I see mention of two additional vibration dampeners supposedly on the fenders up by the headlight assemblies. I can't say as I've ever noticed them.
That "idle compensation relay" was apparently used with certain EZ-117K and EZ-118K systems on '87-'89 740s with B200/230K, B200/230E engines (not North American market). It's shown in manuals living in front of the left strut tower behind the power steering reservoir. Beyond the obvious of it having something to do with idle and being a dotted line optional component, I'm not familiar with its exact function, but ignition module idle compensation is described on p53 in TP30317. It was apparently needed on some engines where the CIS (constant idle system) wasn't fully integrated with the ECU (the way it is in the B230F/FT engines we're familiar with). In the manuals, pin 9 that it's connected to isn't indicated as an input or output, but I supect pin 9 is a secondary load input signal (pin 8 is the primary load input signal from the ECU). It's also connected to the cooling fan motor and climate control system, so possibly had something to do with the magical ECC system available in Europe.
As for your problem in general, you seem to have your heart set on blaming the ignition module, although a flaky rpm governor is really grasping at straws. Amarin concurs with you that it's a definite possibility. It would be nice to be able to temporarily swap one in (a huge advantage for me having two similar 940s). I'm thinking more along the lines of Spook with your distributor and ignition wires. I've had a worn distributor cap/rotor that looked not too bad, but created all kinds of intermittent problems until finally becoming a no start. Any hint of oil inside or at the bottom of the distributor cap from a leaking distributor shaft seal/bushing?
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Dear B.B.,
Hope you're well and stay. I have Volvo TP32043/1 (Bosch LH2.4 Systems) 252 pages, dated January, 1995.
BTW, when were the distributor cap and rotor last replaced?
Hope this helps.
Yours faithfully,
Spook
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Hi again Spook,
Thanks for the info.
I'd like a copy of that plus the new ignition system manual.
Do you have it on PDF? Can you share that manual?
If not, Just having the publication number is a step in the right direction.
I suspect all the ignition parts are OEM and recently swapped but I'll
have to check the service info. I have 1-1/2" stack of service files
on this car from when it was new. Mostly Volvo and some indy shops
worked on it. The list of chronic unsolved problems include this thing where
the car suddenly quits behaving and needing a tow to shops. No amount of breaker boxes helped fix it since it's a stubborn intermittent and tough to fix
when everything seems OK after it's towed to the shop.
Regards, Bill (pooped & off to the sack)
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only valid test for the cps is using a scope and wiggle the harness. resistance is futile. however, i've NEVER seen a flaky sensor cause running problems, usually they quit when hot, ok when cold or quit completely.
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How hard is it to get scope probes at the CPS input ports at the ignition module?
Perhaps the CPS connector is the problem, It couldn't go open without
killing the engine dead, but what happens with resistive contacts?
Would the old sensor have worked by just unplugging and plugging back in?
I wish I tried that first.
My car suddenly went into "limp home" or "The governor mode" was turned on.
(maybe they are one and the same?) Have you measured the CPS signal at the
module with the car running? Is that line free of random hash that might
give the wrong RPM value to the module, and start governor mode?
Do the modules have any filter caps that may be out of limits with age?
I found no ground connection from the metal bolthole insert of the sensor to the ground lead of the harness, so the CPS harness shield isn't grounded at the transmisssion. Is that normal?
How about the main connectors for the fuel and ignition modules, do they
get finnaky and need attention to end these kind of chronic intermittent problems?
Cheers, Bill
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i made a set of typical bosch 2, 3, 4, etc. pin connectors male and female to breakout each connector plus i have a breakout box for the ecus, if needed. in your case, a trip to the junkyard and 3 4mm female banana plugs and go. again, never had a cps cause your isssue and never heard of limp home on lh 2.4. and no, the ecus or connectors USUALLY don't need any attention. unless you reenacted the scene in risky business where the dad's 928 became a uboat.
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LH 2.4 does indeed have a limp home function if the signal is lost from the AMM. The AMM wire has to basically fry to enable limp home mode, which is why we have to manually disconnect the AMM to force limp home mode in cases where we want to isolate the AMM as the cause of a no start and indeed be able to limp home. It's not documented in the LH 2.4 manual that the loss of any other signal forces limp home mode, such as loss of the O2 sensor, block temp sensor, or EGR, which makes sense as these aren't critical for starting and running. The TPS and CPS on the other hand are critical and couldn't be programmed around if their signal was lost. In limp home mode the ECU uses a pre-programmed injector duration. Acceleration will be poor and the engine will badly stumble at moderately higher rpm, which some have attributed to an rpm governor function, but it's simply self-limiting fuel starvation.
Having all those breakout connectors would certainly be handy at times. Wow, a breakout connector for the ECU. I'm trying to imagine what it looks like. I can imagine it being handy for attaching an oscilloscope, but otherwise for multimeter use may not give you much better access than probing at the side of the ECU connector.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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Hi Dave,
Here's an exceprt from TP31397-1 1982-89 700 ignition fault tracing manual
indicating there's speed limiting functions in every Volvo controller.
Maybe this is "Limp Home" maybe it's "speed limiting", whatever it is
I think it's kicking in and out, and don't know why yet.
Do you have a more up to date ignition manual?
Where did the AMM screen wires go? Did they cause the AMM to croak the car?
Bill
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That's a seriously nice breakout box and I imagine worth serious $$. I suppose working at dealer service you couldn't afford to play too many guessing games. You want to know exactly what's going on and be able to easily do the diagnostics by the book.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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been working on volvos since 1988. i know a dead amm has a limp home substitue in the ecu but what was described in the post had nothing to do with the amm.
tried to post a picture of a 35 breakout box---we'll see.
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Dear B.B.,
Hope you're well and stay so. It seems as if a critter found the air box a congenial place, and made some "improvements".
Your site clean-up should clear-up the problems.
Hope this helps.
Yours faithfully,
Spook
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Hi Spook,
Yes, some critter that put foam backed tape in there.
Maybe I should leave some gremlin poison in there?
Seriously, would you care to speculate about this item:
>* Governor Function: EZK module uses the power stage to interrupt every other
>plug, Usually becoming active at 6200 RPM.
What about "Unusally", when this mysterious feature kicks in when not wanted?
Regards, Bill
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Hi Bill,
You may know this already…. I believe you are referring to what’s know as a “Rev limiter”. So you don’t self-destruct your engine! Probably an early version of a “Rev limiter”. They are more common on newer cars.
Jim
--
Will I buy another Volvo??? We'll see....
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Dear B.B.,
Hope you're well and stay so. I didn't intend to convey that some critter installed the foam, but rather that a critter could have shredded the foam, causing debris to impede air flow.
I know nothing about the ignition system's 6,200 revs/minute limitation. I can't recall ever having seen - on my 940s - the tachometer showing more than 4,000 res/minute.
Hope this helps.
Yours faithfully,
Spook
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Hi Spook,
I can't see why there would be tape in the airbox at all.
Sure the 6200 RPM sounds crazy even for a racetrack, but my hunch is that
the EZK module can be at fault for puttting the car in this mode
at low RPMs. The car was running as if only 2 cylinders were firing.
Have you seen the inside of the EZK module? Are there any capacitors in there?
Maybe the next time the car fails like this I should shut down and pull
the plugs and see if two are wet and two clean to support the idea that
every other cylinder shut down with no spark?
Regards, Bill
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Dear B.B.,
Hope you're well and stay so! A "film" of corrosion only a few molecules thick - and so invisible to the unaided eye - can disrupt a circuit. Thus, the sudden onset of symptoms reflects the completion of a corrosion "barrier". It is akin to a faucet being shut: as the handle is turned, the flow of water diminishes and then stops completely.
Removing and re-connecting the Crank Position Sensor (CPS) may break-through the corrosion barrier and restore operation.
Because CPS removal/replacement is tedious, most - who replace a CPS and so restore smooth operation - do not re-install the in-service unit, to see if it has failed internally, or if failure was caused by corrosion.
Your test indicates the CPS itself is OK. The resistance in coil should read 170Ω±30 (Volvo pocket data booklet - Cars , 900, S90, V90 ...] 1991-1998, p. 42.)
Hope this helps.
Yours faithfully,
Spook
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