123quattro

So, this has just popped up in the last 4 days on my 84. Occasionally after shutting the car off on hot days, it immediately won't restart. Cranks just fine, but not even a cough out of it. Wait 5 minutes and it will always restart like nothing ever happened. This happened today when I got home so I did a little more checking. Fuel pump is working normally. Spark is fine as well. This makes me think fuel is getting boiled somewhere? Anyone have ideas where to troubleshoot next?

TIA.

Pics of said car...

WICruiser

Sounds like a leaking injector that dripples fuel in on shut down that clear up with a little time.

If you can access a fuel pressure gauge check to see if the pressure drops off when the engine is shut down.

123quattro

Immediately after you turn it off when it's hot, it won't start. That's with waiting less than 1 second when you re-key it. No matter how much you crank it, it won't even attempt to fire either. I would suspect with an injector, eventually the rail would get re-pressurized and then it would fire. Unfortunately, I don't have a fuel gauge handy to check rail pressure. It's completely related to heat soaking the car though.

Fabio421

The L Jet system has a safety feature that wont allow the fuel pump to work if the RPm is below a certain point. Theoretically (sic) if you have a weak battery or bad ground wire it would have increased resistance when hot which would cause it to crank more slowly. It could be slightly below the threshold of this safety feature.

Disclaimer: This is just a WAG. YMMV

AO

Do you have spark?

123quattro

Spark is fine, it cranks quickly, and the fuel pump is running. It did it today when I pulled into work and I had a friend feel the injectors. Pretty sure they aren't being fired. I'll need to get a scope on them to double check that part.

Anyone know how the engine speed is calculated? I know on the newer systems they use two sensors. I'm wondering if mine has two (crank position plus TDC pin or distributor maybe?), and one sensor is failing occasionally while hot. It wouldn't affect rpm sync while running, but it won't sync on a re-key.

AO

Green wire if I'm not mistaken.

123quattro

Hum. Seems to be getting worse. Car cut out twice while driving today and then died just as I pulled into the driveway. It still started up 5 minutes later.

123quattro

I confirmed tonight that when it won't start, it's not firing the injectors but is sparking and has fuel pressure. Weird.

AO

Is there a Fuel Injection relay that you can try jumping?

123quattro

The only possible engine related relays are fuel pump, jetronic, starter, and burglar alarm. I'll try jumping the jetronic (XVI) tomorrow and see if that has any affect.

123quattro

The relay that powered the ECU, number 16, was bad for those who care.

AO

Called it!