Possible ECU woes

[SilverMT]

Hello everyone.

prior to purchasing my 2003 diesel ZT last November I had found this forum whilst trying to educate myself about potential problems to look out for.

Having learned about the plenum issue I made it a point to check my drains with every wash. I would pour some water down the side drains and feel confident as I watched it all came out from under the car. Little did I know how naive I was being as I thought that this was what was being referred to and never checked the middle drain, under the ECU.

A few days ago my car lost power during a drive. After coasting to a safe parking spot, I tried restarting the car. Turning the key would crank the starter confidently but alas the car would not start. Had I not refueled earlier on I would have suspected that I ran out of diesel.

I noticed that I no longer heard the whine of the diesel pump when turning the ignition on. Theorising that it might be an electrical problem, I fiddled around with the fuses next to the battery, and tried turning the key again. To my surprise, the car started!

Alas, the happiness provided by my newfound electrical genius was short lived as the car turned off again within a few seconds. Another fiddle with the fuses let me start it up again, only to have it turn off once more after roughly the same amount of time. No amount of further prodding to the fuses and relays led to the car starting again, so I had to have it towed to the garage, defeated and disheartened.

I'll try to relay the troubleshooting steps that my mechanic described as well as I can:

He first tested the in-tank fuel pump. Supplying a direct charge made it turn however no fuel was reaching the engine bay before the high pressure pump. It may be of importance to mention that (I believe that) he noticed that when the ignition was off the fuel would arrive into the engine bay, but with the ignition, it wouldn't.

Computer diagnostics apparently gave nonsensical error messages consisting of a string of numbers rather than the usual letter followed by a number.

Upon accessing the ECU box he saw that there was water beneath it. A corner of the ECU box shows a water mark (diagonal lines on lower left corner):


The ECU itself looks like this (doesn't look bad):



Close-ups of lower-left corner:







There seems to be some mineral build-up along some of the traces. To my beginner electronics-hobbyist eyes it looks like the only components in this corner are resistors, diodes and what seem like transistors. Would these have been damaged upon contact with water, or would shorting these have caused damage further up-field?

Would this explain the fuel pump issue or could it be caused by something else? What about the strange error messages? Have I fried my ECU? Should I try cleaning with denatured alcohol?

Thanks to this forum I already repaired the leaking boot, solved a coolant leak issue that turned out to be broken O-rings, and I also replaced 3 rusted door trim panels with replacements from Rimmer Bros.


Losing use of the car to this is bumming me out.

Any advice would be very much appreciated.

Cheers
Ian

[marinabrian]

Hi Ian, that's an NNN100692, so you car is a non EOBD compliant early manual.

In the close up of the board you've pictured the part of the circuit responsible for the injector primary circuit, with a cluster of three resistors including a 3k3, 33k and 15k alongside a transistor, and is not responsible for the fuel pump output.

However I'd say given the creep of corrosion along the shielding tracks to the side of the board, the main processor on the other side of the PCB will have corrosion of the pins, and the whole ECM isn't being initialised.

You could give it a go cleaning up the PCB carefully, but I'm not hopeful given that the diagnostics throw up nonsense

If you get stuck, I can sort this out for you

Best of luck.

Brian

[SilverMT]

Hi Brian,
thanks for the quick and technical reply.
Given the current postal delays, I'll try cleaning it first (I'm in Malta).
If that fails I'll get in touch though.


Would you say that it is a certainty that the fuel-pump symptoms are caused by the PCB corrosion? Or could it be that the PCB is actually fine and the cause is elsewhere?


Something I forgot to mention in my original post is that there are no warning lights on the dash and there are no other obvious electrical issues.

[marinabrian]

, it is highly likely the ECM FPO driver is at fault, the ECM outputs a low signal to the pull in coil of the fuel pump relay on pin 10 of the connecter directly adjacent to the injector loom plug.

Pin 10 arrowed in this picture of your ECM.......


https://the75andztclub.co.uk/forum/a...1&d=1586527916

If you temporarily ground this pin, the fuel pump should run, if it does, then the ECM is almost certainly the problem

Brian

[SilverMT]

I'll run that test and then take it from there.
Thanks again for now.

[Arctic]

Hi Ian.
Glad you posted here as suggested you soon found the answers you needed much quicker than you would have here.

https://the75andztclub.co.uk/forum/s...125864&page=41

[SilverMT]

Originally Posted by Arctic

Hi Ian.
Glad you posted here as suggested you soon found the answers you needed much quicker than you would have here.

https://the75andztclub.co.uk/forum/s...125864&page=41

Hi Arctic,


yes indeed. Thanks for the suggestion

[SilverMT]

Looking at the other side of the board (I don't know why I didn't look at it or take a picture to upload here earlier) revealed a mineral build-up in between pairs of pins on a couple of ICs.


I used contact cleaner and denatured alcohol to dissolve and clean off the contaminants, using a small paint-brush to gently encourage the process. Spraying contact cleaner by itself dissolved the minerals but left them there after evaporating. Hence my use of denatured alcohol. From what I read isopropyl alcohol is better as denatured alcohol contains water but denatured was all I had and I sprayed again with contact cleaner on the clean board. I cleaned both sides of the PCB.



Unfortunately I didn't have the wherewithal to take before and after pictures as seeing the prominent mineral build-up between the IC pins gave me some hope that all was not lost. So I was anxious to start cleaning.


This morning I re-connected the ECU to the car and low and behold, it started after a four or five turns. While I had access to the area, I cleaned and vacuumed the remaining debris and ensured that the drain was clear. My model car doesn't have a drain on the driver's side. I'll buy some aquarium filter material like the one I've seen on here to keep as much debris out as possible in the future.


Thanks to Arctic and marinabrian for your replies, and advice.


Crisis averted!

[suzublu]

The drains are on the floor of the plenum chamber, one under the pollen filter and one under the servo The wing top drains aren't as important

[SD1too]

Originally Posted by SilverMT

I used contact cleaner and denatured alcohol to dissolve and clean off the contaminants ...

Congratulations Ian! That's the sort of car maintenance which impresses me.

Simon