91 964 - Won't stay idling or running

[blair11]

Hi Everyone,

I'm baffled on this one....I'll try to keep it short.
HISTORY
Engine has been fully rebuilt and was running fine for past year in garage & driving up and down the street.
I then drove it to a shop for headliner work
It had been backfiring out of the exhaust a bit at low RPM but seems to smooth out when driving.
Drove it 7 miles to the shop and 7 miles back (first actual drive since the rebuild)
Got it home, tried to restart it the next day and that's when the problems started.

ATTEMPTED RESOLUTION
Thought it might be fuel related....
Drained the gas tank.
Tested the fuel pump after the fuel filter which is working great
Checked fuel pressure which shows within spec when idling but the needle jumps up and down due to erratic idle
Swapped out DME's

I haven't changed out the fuel regulator bc most of the posts read that if it doesn't leak it must be good.
It seems like the fuel pump primes the engine, it starts, uses that fuel and then it dies and won't restart.
If I wait and come back to the vehicle after 15 minutes, it will start again but then the cycle repeats.
I posted a video...any help would be greatly appreciated!

https://youtu.be/jfBaLlOrHQE

[livesportm]

Check the dual distributor belt to make sure they are both spinning when turning the motor by hand and caps off.

[walt]

Crank position sensor? I would check the coils also.

Edit: Another thought is to check the DME relay. Always a good idea to keep a spare in the glove compartment.

[Bobboloo]

Backfire through exhaust is usually an intermittent spark issue. i.e. unburnt fuel igniting past it's intended time. Check that spark plug wires are fully engaged. Distributor cap fully engaged. Check your distributor rotors. etc.

[mysocal911]

Originally Posted by walt

Crank position sensor? I would check the coils also.

Edit: Another thought is to check the DME relay. Always a good idea to keep a spare in the glove compartment.

Doesn't have one. Only has a RPM sensor, and that's good since the engine starts.

[Gavobo]

Have you tried checking the coils ?