SignalSimon

Greetings from England!

I've been looking at a 1987 c4 today - someone's unfinished project which has now been taken on by someone else and has not run for some years. Evidently the previous owner couldn't get it to run.
It needs a whole lot of TLC.
Another mechanic had looked at it some time ago, he believed the VATS may have been responsible for the no-start.

Bearing in mind I've never worked on one before, I did some research on VATS and had a put together a list of tests and workarounds.

Anyway, it turned out the VATS was perfectly fine, pulling in the crank relay and sending the 30Hz to the ECM.
ECM supply voltage was however low at 8.7V due to a corroded fuse.
This was cleaned, ECM supply now a good 12V.

I had spark and injector pulse (noid light) on both banks.

Next test fuel pressure... Zero.
The fuel pump had voltage but wasn't drawing any current.
It failed the bash test so a temporary fuel pump was fitted.
This ran but only developed about 5psi.
I had very low voltage at the pump, the cause was another corroded fuse. Cleaned fuse and holder.
This time, I could hear the fuel pressure regulator hiss on key-on prime and fuel pressure was good at 45psi.

Cranked over, the engine fired a few times but wouldn't stay running.
Turned out only cyl. 3 and 5 were firing.
Checked plug wires vs firing order and found incorrect installation.
I wasn't convinced the base timing was correct due to the orientation of the distributor - it looked a bit advanced but I didn't have my strobe with me so didn't attempt to adjust.

Attempted to start again, this time engine continued to run (but badly) and SES flashing so switched off.

Feeling the headers, all bank 1 were now firing but none of bank 2.

Inspected bank 2 plugs, they were black but not wet.
Checked and cleaned "INJ1" and "INJ2" fuses.

Turned the key on, I noticed the radiator fan started up.
Turned to crank.... Cranks but no injector pulse.
VATS signal present, ignition REF signal present.
Then I noticed the SES light flashing 1,2 then 1,1 repeatedly.

Has the ECM failed? Or is it stuck in a test mode or something?
Tried disconnecting the battery to reset - no luck.
Tried bridging A&B on the ALDL to enter / exit test mode - no luck.
Checked white / black to ALDL for short to ground - clear.
Also checked the PROM module was seated correctly in the ECM.
The sticker says it's an remanufactured ECM so has been changed in the past.

I ended up cleaning the rest of the fuses, which brought the climate and interior lights back to life.
The clock no longer resets at every key-off.
The instrument cluster has a bit more life now but still needs some more work to get everything in order.

A new fuel pump and gasket are on the way.

Any advice on the ECM?

Thanks,
Simon.

Cliff Harris

There is no fuse in the ECM supply voltage wiring. There is a fusible link after the ECM power connector that is connected to the positive battery cable connection at the battery.

The "ECM" fuse goes between the ignition switch and the ECM. Its function is to tell the ECM that the ignition is turned on.

SignalSimon

Fair enough, I had checked the permanent supplies on B1 and C16 were good and found the ignition switched supply on A6 low.

Maybe now I'm back to the original crank,no-start condition that was the reason for the car being stood so many years.

Can't ask the original enthusiast for more information - he has sadly passed away.

Simon.

GaryDoug

Correct me if i am wrong, but isn't code 11 just the code for the CCM reply to diagnostic mode (normal)?

SignalSimon

That's just it... I can't understand why it is in diagnostic mode. I've never jumped A&B on the ALDL other than to try and get it out of diagnostic mode.
I did check for ALDL pin B short to ground and it was clear.
Next time I go round I'm going to check for shorted injectors.
I might take my scope too, it's not an automotive one but will do the job.

Simon.