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Posted by: potomacmidget Aug 25 2018, 02:45 PM

Dear All,

I have a 1971, 1.7L 914, D-jet, original/stock with exception of the muffler system.

Purchased from a fellow board member here, very well sorted car - has been solid for like 5 years.

As of a month ago it starts fine, then after 30 minutes runs rough, backfires and then stalls. Has happened twice, managed to get home by keeping the engine rev'd at 2K RPM and then popping it in gear and keeping it in 3rd reving high, with backfires. Once it stalls very difficult to get it to start again. Both times it has been hot out, have not experienced this before, fuel pump is in the original position and perhaps vapor lock? (but never happened in the past).

Prior to the issues I pulled distributor, replaced the points, condenser, cap rotor, and reinstalled. I exercised caution pulling it an ensured I lined it up properly. I "did" adjust the timing post distributor installation (had to find the faded spots and repaint them) and I adjusted the throttle at the screw by the throttle body. System idled great at like 750 RPM and ran fine - but then the stalling problem previously described started.

I am thinking of the following could be issues:

ignition parts? new but a bad component maybe?
timing messed up? but not sure how it would drift as it starts fine
fuel pressure regulator issue?
CHT issue?
bad coil? acts up once hot?
bad fuel?
bad relay board or D-jet pressure sensor?
bad fuel filter?

Any help appreciated. After the first failure I found I had a leaking fuel injector, leaking from the injector itself(crack). I replaced the injector and it fired up fine, but then 30 minutes later it sort of goes demonic on me...so that was not the root cause.

Thanks in advance,

Reg

Posted by: mark04usa Aug 25 2018, 04:22 PM

Reg,
Your symptoms could well be due to hot weather vapor lock. I would recheck tune, be sure you have no fuel or vacuum leaks, and no fuel hose restrictions, but if the engine runs well until fully warmed on a hot day...vapor lock is a common problem. I still have the fuel pump in the original location on my '70 with D-Jet and had hot restart problems, but a change to Chevron premium fuel helped my car. So, be sure to use a quality premium gasoline.

Good luck sorting out

Posted by: Dave_Darling Aug 25 2018, 11:27 PM

Next time it tries to die, try removing the gas cap. If it sucks a bunch of air in and the car runs OK again, your evaporative emissions system is plugged up.

--DD

Posted by: potomacmidget Aug 26 2018, 05:18 PM

QUOTE(Dave_Darling @ Aug 26 2018, 01:27 AM)

Posted by: Ansbacher Aug 26 2018, 05:55 PM

Been there- Coil, Coil, Coil!

Ansbacher

Posted by: IronHillRestorations Aug 26 2018, 08:29 PM

Fuel filter? Trigger points? Old electric components can get wonky when they get hot, but I'd change your fuel filter before I did anything. It sounds like it's getting plugged and then loosens up after the pressure is off

Posted by: Racer Aug 27 2018, 06:33 AM

I've had similar issues over the years:
1) crud in tank was getting into the fuel filter and clogging it, and would slowly cause the car to stop running. Wait 30 min or so, and car worked fine until the cycle repeated
2) relay board and fuel pump issues. Ran fine. would slowly loose power. couldn't keep running and stall out. Usually harder to restart and time to restart was more variable than in situation 1.

That said, each car is different.

Posted by: potomacmidget Aug 27 2018, 06:35 PM

QUOTE(Racer @ Aug 27 2018, 08:33 AM)

Posted by: cuddy_k Aug 27 2018, 09:15 PM

QUOTE(Ansbacher @ Aug 26 2018, 07:55 PM)

Posted by: TheCabinetmaker Aug 28 2018, 05:57 AM

Definite sign of a failing coil

Posted by: Racer Aug 28 2018, 06:25 AM

On the plus side, while the board has diagnosed it as either a fuel issue or a spark (ignition) issue.. we all agree its getting plenty of the 3rd needed element. . . Air!

Posted by: potomacmidget Aug 30 2018, 07:59 PM

QUOTE(Racer @ Aug 28 2018, 08:25 AM)

Posted by: euro911 Aug 31 2018, 12:15 AM

Change the components out one at a time, so you'll know for sure which component was the cause of failure

Posted by: marksteinhilber Aug 31 2018, 08:20 AM

It might even be the tiny braided mesh ground wire that connects the moving points mounting plate inside the distributor. They go bad and resolderingbthem is difficult and still may not re-establish a good ground connection. I’ve seen that first hand. On cars this old, every electrical connection including the ignition system is suspect.