ben73

My 84 Corvette uses a '8625 PCM.
It's usually very reliable and starts easily after sitting for months on end.

Last week I had to move the car.
It started up just as it always does, but I shut it off shortly after starting to move some stuff that was in the way.
When I went to restart the car a minute later, it wouldn't start and the injectors were dumping a lot of fuel while cranking.

The odd part is that when the key is on, but the motor is not running, when I press the pedal the injectors buzz and spray fuel. This is not normal.

If I disconnect the battery for a while, it stops doing this for the first start attempt, but then the buzzing injectors return after one failed start.

I have swapped my ostrich equipped PCM for another with a known working burned EEPROM, but it does the same, so that rules out the PCM.

When I datalog, all the important sensors appear ok. TPS, MAP, CTS all good.

I know my way around this car very well as nobody else has worked on it during the 15 years I've owned it, but this has me scratching my head.



Any suggestions??

RBob

iTrader: (1)

If the PCM thinks that the engine is running it will enable AE. Which will do exactly as you mentioned. Buzz the injectors and spray fuel.

May be a bad ICM in the distributor. But then again this may be some sort of feature of the '8625 code mask that you are using.

I know that I had modified the '7747 code to do this. Eliminated the long cranking times with a dry TBI manifold. Removed that feature as it made it easy to flood the engine. Same as the pump shot on a carb, needed to be careful while working the throttle body.

RBob.

ben73

Thank you RBob, that sounds very logical.
I was going to swap the distributor, but couldn't see how that would fix it.

I will look for a 'engine running' status and also disable AE in the tune to prove your idea.
It's like the 'running' flag is being set during the first failed start after a battery reconnect.
I did notice a 'bad shutdown' flag, but I don't know what that means.

Will report back

THANK YOU.

ben73

I swapped the ICM from my spare OEM distributor into the Davis DUI, no change.
I tested the pickup coil in the DUI and it appeared ok.
I installed the old OEM distributor and it is dead. No spark, no injector pulses.
So I reinstalled the DUI and figured it was time to clean the plugs and turn the motor over with the plugs out after injecting so much fuel without a successful start. I then fired it up with the injectors disconnected to totally clear the cylinders and it ran properly.
I reconnected the injectors and it's fixed!
I don't know if I inadvertently fixed a bad connection during the testing, or if it was all a case of old fuel and fouled plugs because all I have done is idle this car around the workshop each time it gets in the way..
The AE without the motor running made me think something odd was happening as I have never noticed it doing that, but then again, it rarely fails to start first time, so maybe that's normal?

Anyway, it's fixed. Thanks RBob for your input.

Buccaneer

Nice Ben. NOW, get crackin' on that car and make some good runs.