Volvo RWD 900 Forum

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Wouldn't start 900 1993

Hi All,

Out on errands my car would not start after coming out of the store.
Three tries including some waiting, no dice.
This never happens, the car always starts up quick.
So instead of replacing the Fuel relay, RSR, CPS, fuel pump, etc.
I disconnected the battery ground cable for two minutes to reset ECUs.

Reconnected battery and it started up like nothing was ever wrong.

Dang, I forgot to pull OBD codes first!

It reminds me of Bill Gates go-to solution for software problems:
CTRL-ALT-DEL

Go figure.

Bill








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Wouldn't start 900 1993

Sorry, Bill, really reeks of a bad CPS to me. Let me guess, no Check Engine during cranking, right? A bad CPS rarely ever sets a code. Also, 99% of the time, no Check Engine then no code, especially fatal codes. I have trouble believing it was the ECU reset that got you going, more likely the extra few minutes of cool down while you fetched a wrench and gave it the two minutes. I know you're always quick to figure it's bad caps, but that's the last thought I usually have. My ESR meter can of course find all kinds of aging caps if I go looking. And what about surface caps, do you check and replace those? I can't remember if and how many are in those old ECUs. Of course if you now go for a good used one, it will still have old caps close to working threshold.

Now I had a very similar situation just a few months back. Cold start normally okay, but warm restart not reliable. I got caught out shopping a couple of times. Thought I was going to wear the battery down cranking away, so would take a few minutes break. Often, just when I was about to finally give up it would catch. One day no such luck and I could tell I was pushing my luck on the (newish) battery. I had frozen food melting so called my wife to come get it, also figuring I could use hers for a battery jump as needed or drive me home after a tow truck. 20 minutes later she arrives and I start cranking again, fired right up like nothing was wrong. Would run fine for days and I was too busy to start diagnosing an engine that was running perfectly fine.

One day I had a cold no start, actually the third one. Now having the time, I opened the hood and without hesitating started by checking the integrity of the CPS cable. Hadn't even changed into work clothes. Pulling it off the standoff clips and the insulation immediately cracked and peeled there. A couple of minutes to fetch a 10 mm ratchet, extensions and a universal and it was quickly out, revealing the classic insulation split at the sensor. I thought I had a spare CPS, but forgot I'd already used it. Phoned the local indie shop asking if they had a Bougicord or how long it would take to bring one in from the regiinal distributor. He said they could get me a Facet that day. Said that's the one they were now using and liked, also cheaper then Bougicord. Made in Italy, you can tell it's high quality. Facet is OE for a number of makes. I'm betting as good, if not better than Bougicord. They even include the standoff clips (NLA separately from Volvo). You don't get those with thd Bougicord, but do with the Genuine Volvo CPS. I'm now not going back to Bougicard if I can find a cheaper Facet. I found a really good deal on a Facet on Amazon or Ebay (I forget) and bought it as my new spare.
--
Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now








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Wouldn't start 900 1993

Hi Dave,

I do recognize how many seasoned techs swap out CPS's, and insist on OEM vs
unreliable after market CPS's.

What's the right coil resistance for the CPS?
I swapped out a Volvo 3547847 that looks like new and the coil tests 174 ohms.
I could dig through the service records to see when it was put in.

The replacement is a "Karpal 1KP VL 1005 001" - 1389399-5, 3547847, 35478478
Made in China

How do you explain the car starting immediately after reset the ECUs.?
And then working like normal.

I'm wondering if ECU reboot will work so well after my next surprise
shutdown that could be today or next summer.

See my post to Amarin for more speculative details.

Best regards, Bill





























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Wouldn't start 900 1993

Dear B.B.,

Hope you're well and stay so!

For the Crank Position Sensor / RPM Sensor (Volvo #3547847) - used in and after 1991 models - coil resistance is 170Ω ± 30. Source: Volvo, pocket data booklet - Cars 700,850, 900 (1991-1996), p. 40.

Sometimes transient conditions disrupt electrical systems. Thus, the SRS warning light may suddenly illuminate, for no obvious reason Disconnecting the negative battery cable clamp from the negative battery terminal - and waiting 10-20 minutes - usually re-sets the system.

At the risk of laboring the obvious - for which forgive me - auto electrics are subject to temperature and humidity changes: metal expands and shrinks. A coating of corrosion a few molecules thick - so invisible to the unaided eye - can disrupt a circuit. Corrosion increases resistance, sometimes to the point where power doesn't flow. But if the connector vibrates - e.g., when the engine is turned-on - the contacts may move just enough for current to find a path. The same is true as to heat.

Hope this helps.

Yours faithfully,

Spook








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Wouldn't start 900 1993

Hi Spook,

Thanks for the info.
Klaus sent me his pocket data book but its 1991-1998 TP 0302207
I can find all of the sensors under LH2.4 components but NO CPS
or RPM sensor?
It's a great book, but I told him to get better and I'll send it back.
He's still hanging in, and in good spirits, but not very optimistic.

There's a number of ECU lines with series connectors, looking like bullet
connectors.
Some are high up near the firewall on both sides of the engine bay.
There's a bracket between the firewall and the top of the strut mount that
the connectors are tie-wrapped to.

Whats your sense of any risk in taking them apart? If the female pins
corrode onto the bullet connector and or the material supporting the female
pins fails, it's a nasty job to fix.

Is there some good way to service the connectors without taking them apart?

I think Blindboy ran into this where his RSR connector crapped out.
I have photos of directional light socket failure with this sort of bullet pin.
Pictures on request, Brickboad wont upload pictures anymore.

Cheers, Bill








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Wouldn't start 900 1993

Dear B.B.,

Hope you're well and stay so!

The problem with the "bullet" format wire terminals is that they're secured to the connector housing with some sort of polymer "bushing", that goes over the wire/wire terminal and fits snugly into the housing. This polymer deteriorates with time.

When one tries to separate both sides of the connectors' housings - so that an oxidation-dissolving chemical can do its work - the bushings crumble. That leaves the wire terminals loose inside the connector's housing. Each wire's terminal then has to be matched to its mate in the remaining half of the connector

Under the steel brace - that connects the driver's side strut tower to the firewall - there's an eight-wire connector (C54 on the 1994 Volvo "Green Book' Wiring Diagram). There's precious little slack in the wiring harness, so manipulating the wire terminals is not easy. The hood's hinge makes side-access hard, even with the hood in the full, upright position.

Even so, having removed one of the now-useless gray terminal housings, I was able to mate the wires. I have small hands, so had just enough work room. A large-fingered mechanic will need to use a mini-needle-nose pliers to grip each wire terminal connector and push it into place.

I used a cloth-reinforced sticky tape to make a "boot" over the end of the wiring harness, where the now-separate wires each goes into the remaining connector housing. I hope this "boot" limits humidity-laden air's access to the wiring terminals.

In all this, I'm glad that corrosion had not bonded the wiring terminals: the connector housing halves separated easily. Had the wiring terminals corrosion-bonded, separating them would have involved applying a corrosion-remover and then one-by-one trying to break the corrosion bond.

It might be easier to cut-off the terminals and solder the wires, having first slid heat-shrink tubing over each wire. I'm not sure there's enough slack in the wiring harness to allow this to be done. Even if there's enough slack, the task would take several hours to do, because of difficult access.

Removing the hood would help. A helper is needed to do that. Removing and then re-aligning the hood - which I've never done - is not likely to be easy.

Hope this helps.

Yours faithfully,

Spook








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Wouldn't start 900 1993

Hi Spook,

You share my opinion that you shouldn't fiddle with those harness
bullet connectors that Volvo used to build the car.

What do you think about the big ECU connectors?
Any sense of them needing attention?
Do you know of service issues caused by ECU connectors?
If so, how to service?

Thanks, Bill









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Wouldn't start 900 1993

Dear B.B.,

Hope you're well and stay so. "De-corroding" the C54 connector required separating both halves.

As the ECU is inside the car, I'd guess corrosion on ECU connector terminals could only be a problem if the car lives in a high-humidity region and is parked outdoors.

You may recall that Takata airbags - not used in rear-wheel-drive Volvos - are most likely to turn into a "fragmentation grenade" on deployment, in cars that "live" in hot/humid areas. Humidity destabilizes ammonium nitrate used to generate the nitrogen that fills the airbag.

Based on years of reading posts, I don't recall many reports of problems with corrosion on ECU connectors. Should that occur, the ECU connector's design is different and more robust.

Thus, if corrosion is suspected as a source of malfunctions, separated the connector from the ECU, having first disconnected the negative battery cable clamp from the negative battery terminal. Then, spray DeOxit or a similar aerosol corrosion remover on the ECU's terminals and on the connector's terminals. Allow to dry. Re-seat the connector on the ECU. That should restore full connectivity.

Hope this helps.

Yours faithfully,

Spook








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Wouldn't start 900 1993

Hi Spook,

I see a 5% spray and a 100% brush-on version of Dexoit.

Any comments about which works better for the Modules and other connectors?

Have you seen this info re: zinc paste:

http://sw-em.com/anti_corrosive_paste.htm

Bill








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Wouldn't start 900 1993

Hi BB,

Regarding Zinc Paste:

In older cars they used brass or copper alloy (copper mixed with other metals) to prevent corrosion at the metal contacts. You know this from the "yellow-tinge" of the metal. In modern cars such as 900 series most electrical contact are already zinc-plated. Thus there is no need for zinc paste. In older cars yes. How to know if its already zinc plated? Look at the colour of the contact metal, if its "silver-white" then its already zinc plated.

The contacts of AFM, CPS, O2 sensor, ECU, ICU, fuel injector, idle valve and some relays are ALL zinc-plated.

The bullet type contacts at the firewall engine harness are ALL brass thus you could see some corrosion there. The RSR electrical contacts are also brass. Needs cleaning once in few years.

Thats why you'll see posts about reflowing the RSR once every few years. Once every few years is not long enough to cause any solder connection to crack. Its just that by removing and reinserting the RSR from its connector cleans the brass contacts.

A better than zinc contact plating is gold. Unfortunately its expensive for automotive use thus only available for more specialised items like for audio connectors in my hi-fi hobby.

Rhodium plating is also better than zinc but still expensive. Also used on some audio connectors in hi-fi and some very specialised use such as reed relays because rhodium is also a hard-wearing metal for the relay's internal contacts.

Don't use any abrasives (steel wool/fine sandpaper/glass fibre pens) to clean the zinc-plated contacts as the plating is very thin (few microns thick) and could wear them out. Use some ISOPROPYL alcohol on Q-tips and blow (or let) them dry.

Many many years ago I got rid of those brass contacts of engine firewall harness. I solder those wires one-by-one and put some heat-shrink over them. Spent the entire weekend doing this from morning to evening. Until now i have no issue with firewall harness. I figured long ago that harness replacement its not going to happen in lifetime of the car. And the 900 series harness is not biodegradeable type.

Hope these helps,
Amarin








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Connectors 900 1993

Hi Amarin,

Little by little I'm becoming amazed about how you have souped up your
wiring!

Did the bullet connectors fail before you wired the firewall connections direct?

Would filling them with dielectric silicone initially have extended the life of those connectors?

Did you use non-insulated butt crimps before soldering and shrink wrap?

Perhaps the general disdain for after market CPS's might be caused by un-plated connectors acting up with dis-similar metals for contacts?
If so, maybe they would become more reliable with zinc paste?

Best regards, Bill









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Connectors 900 1993

Hi Bill,

"Did the bullet connectors fail before you wired the firewall connections direct?"
No. The corrosion on these brass connectors never got that bad. Besides I was doing the cleaning once every few years. I got tired of doing this so soldering them was the solution. I also realised the 900 harness generally don't need replacement unlike those on 200 700 series. Plus I don't see any replacement harness for 900 series on Dave Burton's website while it was still up last time.


"Would filling them with dielectric silicone initially have extended the life of those connectors?"
Yes.


"Did you use non-insulated butt crimps before soldering and shrink wrap?"
No. I just strip-off the wire's insulator and twist them together before soldering. Remember to put the shrink-wrap down the wire before soldering. If you solder for too long the heat transfer might shrink the wrap before its intended use so put some insulator under it, maybe a small piece of paper or masking tape. You can't park the shrink-wrap further down the wire while soldering as the rest of them is under plastic tubing. Some bigger gauge wire might need longer (5-10 seconds) soldering time and repeated soldering. Using a 30-40 watts soldering iron is a must as soldering these wires need more heat than those on circuit boards.


"Perhaps the general disdain for after market CPS's might be caused by un-plated connectors acting up with dis-similar metals for contacts?"
Its possible. Haven't think of that before. Yes zinc paste might be helpful.


Best regards,
Amarin








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Connectors 900 1993

Hi Amarin,

"Perhaps the general disdain for after market CPS's might be caused by un-plated connectors acting up with dis-similar metals for contacts?"
Its possible. Haven't think of that before. Yes zinc paste might be helpful."

Maybe careful application of Copper based anti seize such as Loctite C5-A
is a better solution for deterring connector failures from the elements and
dissimilar metals? It might work best on connectors that have no danger
of shorting out to adjacent pins improving conductivity long term ?

Whatsay? Bill








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Connectors 900 1993

Hi Bill,

"Maybe careful application of Copper based anti seize such as Loctite C5-A
is a better solution for deterring connector failures from the elements and
dissimilar metals?"

I think that was meant for mechanical work (ie. anti-seize) not electrical

About contact corrosions, the primary issue here is sealing them away from the "elements"

Our car already using "sealed" connectors (well...except the battery posts) so the "element" part already taken care of

Dissimilar metal don't corrode by themselves unless the "element" part is there too

Coating the contacts with dielectric grease also works well to seal them away from the "elements"

If you also meant to use the copper paste as contact enhancer (copper conducts better than zinc) then don't. There are better contact enhancers available, one of them is Stabilant 22. Used by Boeing and NATO in their equipments.

Amarin











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Wouldn't start 900 1993

Hi BB,

I don't think any ground loop or RFI issue can be solved by resetting the ECU. Clearly the ECU has some issues and for this incident its unlikely solely due to aging capacitors. I guess there could also be solder joint micro-cracks on the ECU board. Yes need "opening up" to really diagnose. Meanwhile get some used ECU on the eBay. No re-programming needed as these ECUs are hardware based.

Amarin.








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Speculation mode 900 1993

Hi Amarin,

It's good to hear from you.
Have you been watching Laser headlights?
They're 4X brighter in new Audi's and maybe VW's now.
Lasers sound dangerous if aimed wrong, but they must have overcome that to go into production. Good for another post.

I'm in the speculation mode here, and glad to discover another temporary
fix for this intermittent fault that's documented by the service records
and notes from the refreshingly honest previous owner.

I don't see a ground loop problem at all, but that's likely why Volvo didn't
ground the RPM sensor harness at the bell housing.

I'll be interested to see if ECU reboot gets the car running after the next
surprise shutdown.

Elecrolytic caps aren't the only caps that fail / go out of limits.
I've seen other types fail causing oscillator circuits to quit and
kill some machines. This is why replacing caps in the old ECUs is a good idea.
Using the highest quality long life caps, and NOT old radio shack and flea
market parts as some people think.

One engineer at the UK site designed a LH mod for the fuel pump control based
on a 555 IC Have you seen it, and heard any reports pro or con?
It's buried in the UK FAQ, maybe our 700/900 FAQ?

****Connector faults*****
Look at this recent AWD post where it looks like a problem with a throttle
control module connector.
Start with the May 7th post This was a new fault after BZ resolved his vaccum leak.

https://www.brickboard.com/AWD/volvo/1688720/V70-XC70/2002_v70t24_engine_rpm_surges_idle_cold.html

*What's wrong with his connector?

Unfortunately BZ has a track record of asking questions and disappearing for
months until he has another question. He doesn't bother to report back
what he and/or his dealer did to finally solve his problem.

*Zinc Paste ACZP
ACZP was first suggested to me by wiring guru Dave Barton.
Look at this very interesting article by Brickboarder Ron Kwas.
http://sw-em.com/anti_corrosive_paste.htm

(His article highlights other problems with volvo connectors, for instance
toasted relay sockets for fuel relays where people were blowing 30 amp fuses
in a 25 amp circuit, and the normal current draw is around 11 amps
loose pins draw current when arccing and make a toaster it seems.)

*What's the best way to service connectors?
Clean (Beware strong solvents that can wreck bullet connectors)
I've used 90% isoprpyl alcohol and scrub with a toothbrush, blow off
with compressed air
Deoxit- when and where?
Repair or replace loose/bad pins
What lube?
Penetrox A is not compatable with rubber or polyethelene insulating materials
(Beware of destroying bullet connectors with the wrong chemicals)
Penetrox A-13 is OK with the above and very pricey
Dielectric silicone
Spray silicone
Copper based anti seez applied carefully so as not to short out any pins?
other?

Also see a section of the 700/900 FAQ Oxidized connectors. (pg 66)

I looked at LH and EZK interconnections and found several series connectors:
C2, C3, C50, C51, C54
Some of these are by the driver side firewall tie-wrapped underneath a bracket
to the strut post. I'm afraid to take them apart after having the OBD port
connector insulation fall apart. (photos on request)

Shielded cables for LH and EZK.
I found no shielded cables for LH.
EZK has three:
7/24 Knock Sensor connector C132 pin 7, pin 6 gnd to EZK 12,13
7/25 RPM (CPS) C156 pins 1 & 2 coil, pin 3 gnd to EZK 10,23,11
4/15 Power stage pin 5 to EZK pin 16 (output control line)
pin 3 gnd

I have a snap ferrite to put on the CPS harness, that wont hurt and
can help reduce any RFI pickup that can upset the RPM signal.
Maybe the fault is with CPS connectors?

I can only speculate why the ECUs locked up.
Old ECU caps, RFI, faulty connectors? Does the LH ECU need a mod?
I wont be surprised if the ECU will behave normally for 3 months before another
surprise shutdown. So this is the nastiest of faults to correct.


Here's the plan for the next time it quits:

First grab any OBD codes from ports 2 and 6.
Instead of reading current on fuse 1 and 11, just check for +12V at fuse 11
with the probe on either leg up top of the ATC fuse F-11.
If there's no 12 volts then FUEL is shut down via either of two fuel relay
coils & points or the LH switching ports 21 and 20.

The ECU controls switched grounds to enable both fuel relay coils,
both lines through C3 connector somewhere in back of the glovebox.
How hard is that to find?

In the off chance I get ambitious:
Test LEDs or 14v grain of wheat lamps on pin 1 and 5 of the fuel relay socket
to check 12V at both fuel relay coils.

Jumpers to fuel relay socket pins 2 & 4 to ground could bypass a failed LH ECU
to operate the relay and determing if ECU swiching failed.
It would quickly enable the fuel circuit including both pumps if LH crapped out.

****** WARNING ***** (For anyone reading this)
Jumpers to be used ONLY ON A TEMPORARY BASIS! Jumping those FI relay points would defeat program safeguards and keep the fuel pumps running ALL the time, including after you shut down the car and remove the key.

Best regards, Bill








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Speculation mode 900 1993

Hi BB,

Its good to hear from you too!

Its bright and sunny Sunday morning here in Malaysia. At my job as Forensic Pathologist (thats Medical Examiner in the US) I usually don't heed speculations as they could be too absurd sometimes : ) No homicide case that needs my expertise yet today so I think I'd do some answers to your speculations!



Speculation no.1 - Audi "laser headlights"
I think thats more of marketing term in order to sell their cars better, for those buyers thats technologically inclined. Laser as you know it is a single waveform of light. Thats why you have red or green lasers. No white lasers by the way! Because you and I know white light is a mixture of colours! So thats one misnomer made by Audi. If their pixellated "laser headlight" could project some pictures on the road then might as well put some "conference room" LCD projector on the car's hood to light up the way. LCD projector nowadays are very bright too. Use some 12V DC to AC MOSFET inverter to power up these projectors on the car. By then you could show some animated pictures on the road too! Like to inform the pedestrian its ok to cross the road now?? Come on Audi you could do better than misleading the public. Sometimes I think these Germans are too much. "Desperate" is the word that comes to mind!



Speculation no.2 - The 555 IC fuel pump controller
Here's the web link:
https://www.volvoclub.org.uk/faq/EngineFIComputer.html#ECUFuelPumpControlCircuitRepair
Simply said this circuit is for those owners with faulty LH ECUs (ie unable to activate fuel pump relay). The circuit is supposed to use CPS signal from pin1 of LH ECU. That signal actually came from pin17 of EZK ECU as the CPS connects directly to EZK (not LH). If you repair (reflow solder) or recap your ECU I think you won't need this. That time the article was written ECU repair was expensive (still is) and most of used ECUs also expensive. Used ECUs are cheap now at eBay.



Speculation no.3 - Volvo didn't ground CPS harness at bell housing
I think you're referring to the CPS harness's screen ground. Yes its true Volvo didn't do that. The bell housing is also electrically grounded by its mating to the engine. Why then the CPS harness's screen is still grounded to EZK which ultimately uses intake manifold ground? I guess its good engineering practice to reference any sensor's screen ground back to its sensing circuit ground first. Don't agree with this? Many 900 cars are still working with this stock ground configuration.

Isolating the screen ground with capacitors (means no direct ground connection) usually works well in power supply designs (usually for switched power supplies) where the interference frequency is known (this to calculate the microFarad value of the isolation capacitor). Can't just cherry pick any capacitor and expect it to work.

Snap ferrite is usually installed in supply wiring like from power adaptor to laptop or mains input in switched power supplies. I've yet to see snap ferrite installed in sensor wiring. I guess you're being super-critical here.



Speculation no.4 - Your plan of what to do when it quits

Measuring here and there is good when you know what to expect and do next. Not if you're still beating around the bush. Maybe you could watch "Pine Hollow Auto Diagnostics" (PHAD) at youtube on how to do that. My favourite channel too, almost daily watched. Ivan's into using laptops, pico sensor, cylinder pressure sensor, current sensing devices in diagnosing problematic cars. My observation (and also to my relief) is that not one of 900 series Volvo needed these steps.


Hope these helps,
Amarin








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Speculation mode 900 1993

Hi Amarin,

Thanks for all the comments.
OK about being a forensic pathologist. Years a go a ham radio friend, a dentist, got bored and went back to school to become a pathologist.
He helped me quit smoking when he explained what smokers and non-smokers lungs look like.
He did me a huge favor.

I did some more looking around LH circuitry and noticed two "Bridge connectors"
by the LH module harness: 18/1 & 18/2. They make a jumper between LH pins 19 & 29.
These look like Volvo diagnostic ports. Do you know anything about this?

I looked again at your posts Sep/Oct 2022 and nice photos of the EZK module.
OK about the hassle with plated through holes on PCBs. I was introduced to that issue in the early 80's having to repair Kenwood TS-930S, and TS-940S transceivers that had a huge problem after Kenwood forgot how to wave solder. The ugliest to fix is when the plated through holes are buried under an LSI.
You have to become skilled with solder wick and/or solder suckers.
BTW Kenwood never owned up to it. :-(

Do you have more photos of the boards and plated through holes?
I would first look at LH circuit traces out to C3 and the (Main Fuel relay)

I use a Opti-Visor magnifying headset here. Maybe there's something better?

Buying a used module will be a last resort here, since it probably is also
full of bugs. I'd rather fix the devil I know.

Another cool comment you made, is worth repeating for the gang.
If your engine quits.
Clear the ECUs simply by pulling Fuse 1
Wait 2 minutes to put it back and see if you get lucky.
Be sure to post back to share your results.

Thanks, Bill








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Speculation mode 900 1993

Hi BB,

Those jumpers are for grounding pins 19 and 29 to the intake manifold. They are not meant as diagnostic port for these ECUs for any user to connect laptops, scanner or diagnostic equipment. The plated thru holes are less likely to be problematic in these ECUs. They look like "pin-head sized" solder blobs on the board. These carry low level signals between two sides of the board. They are seldom found with micro-cracks. The micro-cracks are usually found at the solder side of LH/EZK connector pins. Anyway the real culprit is still those aging capacitors.

Yes I have other ECU photos but now it seems difficult to post it on the board. Sometimes the connection would just terminate while uploading a photo. I'm using my Macbook laptop for this. Weirdly I could still use my Android phone to read the board but the photos are in Macbook. Even if I transfer them to the phone its difficult to manipulate them on that tiny screen to post it on the board.

Buying a used module is like me like saying "if repairs unsuccessful at least you could plug in the used module in order to continue using the car". I meant it as backup plan. If you have another car in the meanwhile then this isn't an issue.

I'll try to upload the photos again in the meantime.

Hope these helps,
Amarin








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ECU photo error 900 1993

I can't upload any photos. This has become worse. I've used chrome and safari. Both can't work. Got error message as below:


The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, webmaster@localhost and inform them of the time the error occurred, and anything you might have done that may have caused the error.

𖝛]ERR: 24: Error in Perl code: Died at /home/www/lib/AWS.pm line 33.

Apache Embperl 2.5.0 [Sun Jun 18 15:06:46 2023]


Amarin








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ECU photo error 900 1993

H Amarin,

Brickboard has not accepted uploads for months.
Profiles and user mail is busted too.

Look here for a workaround by Kittysgreyvolvo.
https://www.brickboard.com/RWD/volvo/1688787/444-544/uploading_image_brickpix_gallery.html

I wondered why you serviced your firewall connectors every two years.
You don't suffer corrosive salt bath that we do in the winter rust belt.
Then Wikipedia.org told me about the nasty brown haze air pollution there.
A variety of nasty chemicals in the air.
Was this what was effecting your connectors?
Maybe you should move to New Zealand in the dry season?

Today I found this while searching for something else in Volvo pubs:

"WARNING: Do not use ignition switch during compression tests on fuel injected vehicles. Use a remote starter to crank engine. Fuel injectors on many models are triggered by ignition switch during cranking mode, which can create a fire hazard or contaminate engine oiling system."

Using the starter service port (key out) does not enable Ignition and prevents possible arcing damage to ECU's.

Best regards, Bill








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LH photos 900 1993

Hi,

Another share from Google Drive

https://drive.google.com/drive/folders/1F90TdZjUHJr4kFa4ZGrSb_Ti5VcoFWr_?usp=share_link


The jumpers are done because of damaged PTH holes on board. The PTH doesn't connect both sides of board AFTER soldering. Always check for continuity (the PTH) with multimeter AFTER soldering.

The small white "hybrid-analog" board is supposed to control over fuel pump relay activation. The 555 IC circuit was made to bypass this. This hybrid-analog board was problematic in old Porsche's LH ECU (circa year 1986) but not in Volvo's in my experience (my experience only covers 1994-1995 ECUs)

Here's the link about Porsche's issue:
https://www.jdsporsche.com/ECU-repair

Also included are photos of my spare 935 ECU from eBay made in Germany. It uses 3 resistor jumpers. But I'm currently using 935 ECU from Spain (original to car). I like original ECU better as engine running is smoother.

I can tell that the Germany ECU is older than Spain as its still using Philips ON823 as injector driver transistor (Darlington type). This part is already obsolete. Unobtainable from electronic stores. The Spain ECU is using Fairchild BDX53c driver transistor (also Darlington but non-obsolete). Maybe this one have better injector control.

Amarin








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LH photos 900 1993

Hi Amarin,

Thanks for the detailed photos and comments.
The Porsche ECU repair site was good too.

re: Board with Phillips caps (side view)
Did you check EZK C903 ? a rectangular green block "ERO" cap?
It's adjacent to a crystal and likely part of an oscillator circuit.

The coating over the board can be carefully scraped off around the PTH's
so that solder flows to the PCB track when you reflow.

PTH's are a pain where you sit down, the last two I repaired with a jumper
on the instrument cluster flex board, it was the +12V leg to the fuel gauge working and quitting with it's own perverse schedule to give troubleshooters misery.

Look at PTH.JPG upper right
just between D332 / D504 and T322
for a solder joint that looks like it needs attention.

I wonder if the Siemens 30191 voltage regulator mounted on the big heat sink might benefit from new thermal compound?
It looks like it's riveted on to the heatsink.

When I get my ECU out I'll try placing the PCB over a strong light and see if
the photo will highlight the PCB tracks better.
I'd look first at the legs for the RPM signal.
Good closeups blowup great with the PC to help survey the board.



Some handy tips from the Porsche guys to share here:
The LH2.3 ECUs are very easily damaged by voltage spikes and surges. We recommend:

Never try to jump start the car
disconnect the battery earth (ground ) lead and charge the battery first.

Never use a “rapid charger” with the battery ground connected.

Never do welding on the car without disconnecting the battery
AND also disconnecting the 35way connector on the LH2.3 (and the EZK!)

A faulty alternator, which allows the battery voltage to rise above 16v can destroy the ECU.

Never do any electrical work on the car without disconnecting the battery,
if at all possible.
Otherwise at least make sure the ignition is switched off – at your risk!

Flashovers from faulty ignition leads can damage the ECUs

Connecting the battery with reverse polarity is a sure way to toast your ECU's



The Porsche guys calibrate the AMM? Is there some adjustment in Volvo AMMs?

Best regards, Bill








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LH photos 900 1993

Hi BB,

Hope the photos are satisfactory. These were taken with my Android phone.


"Did you check EZK C903 ? a rectangular green block "ERO" cap?
It's adjacent to a crystal and likely part of an oscillator circuit"
--> No. I didn't suspect anything wrong with the MKT (metallized polyester) cap. Yes its a part of oscillating circuit because that Siemens microprocessor is basically an 8-bit 12MHz computer. The 12MHz speed is determined by the Xtal oscillator. I've read Siemens's datasheet sometime ago that you could increase the speed by upgrading the Xtal but that won't increase the car's horsepower. Increasing the speed would make the microprocessor runs hotter than usual that might require extra cooling (attaching heatsink or add fan maybe).


"The coating over the board can be carefully scraped off around the PTH's
so that solder flows to the PCB track when you reflow."
--> Exactly. One more helpful thing is to use soldering iron with pointed tip.


"Look at PTH.JPG upper right just between D332 / D504 and T322
for a solder joint that looks like it needs attention"
--> Already done afterwards.


"I wonder if the Siemens 30191 voltage regulator mounted on the big heat sink might benefit from new thermal compound? It looks like it's riveted on to the heatsink."
--> Yes its riveted. I think its ok to let it be. I did think of additional cooling like a small fan with ventilation hole (cutting hole to the plastic EZK box) but that would introduce outside dust to the components. The board is almost dust-free as it is. I did wonder why the EZK box is not a Faraday cage like the all-metal LH box. Anyway the car still works.


"The LH2.3 ECUs are very easily damaged by voltage spikes and surges."
--> Could be but for our LH2.4 ECU there are MLCC (multilayer ceramic capacitor) soldered to every connector pins on the board. If you look closely at bottom of the pins at board-side there's a row of small brown square things (ie MLCC). I think these are to absorb voltage spikes.


"Is there some adjustment in Volvo AMMs?"
--> Only for LH2.2 I think. Its supposed to be adjusted with a CO meter attached at the exhaust tip. Aimed for less than 0.5% CO level if I'm not mistaken. However no adjustments for LH2.4 AMM.


Best regards,
Amarin








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EZK photos 900 1993

Hi BB,

Good idea to use file hosting website. Here's first try from my Google Drive. These are photos of EZK ICU.

https://drive.google.com/drive/folders/120-V7mNPV7UWZ6HzSSU3oVfSsBwA6AbQ?usp=sharing

Amarin








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Wouldn't start 900 1993

Keep us posted on whether this happens again. So it cranked with no start?








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Wouldn't start 900 1993

Hi ?

It cranked fine but it acted like the ignition was shut down.
Just rebooting the ECU (s) got it working.
I goofed by not checking OBD codes to see if the ECU reported why it quit.

This problem smacks of ECU corruption.
The good news was I didn't need a tow home, with the ECU reset.
The Bad news is how do you pinpoint the exact cause of the problem?

When I recover from my shoulder replacement I'll replace the geriatric
electrolytic caps in the ECUs and service the connectors.

I think I'll keep my harbor freight ATC fuse current tester in the car
and if this fault repeats I'll check fuse 1 & 11 to see if the pumps are
drawing current. I'll try to get more info about the fault.

Bill












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