83 cranks but won't start (SOLVED)

[GeorgeT]

I had a similar issue with a failing double relay.

[Odoyle]

Ok update, replaced the voltage regulator with a NOS bosch unit. Brushes on the old regulator where right at the end of their life. I stuck a light in engine bay near the alternator and saw there was a loose bullet connector coming from the red wire on starter, I sanded the bullet and reconnected it. Alternator now has 13.8V at battery when running, so that's definitely fixed. So now I'm driving the car, starts fine in the morning when cold, park it in sun, cranks but won't start. Let it sit for another 20 minutes and try again and it starts. Talked to Mark Allison and said he had an 82 come in earlier this year with same problem, they replaced the marelli coil with a new bosch coil and it fixed problem. I have since bought a bosch coil and replaced my marelli coil, have only done a couple short drives, but car is starting every time, have yet to leave it hot in sun, but will do this week and update.

[Odoyle]

Update: I let the car idle in the garage up to around 190F, fan kicked on, car shut off. It will crank but not start after that. I restarted it 20 mins later it got to about 190F then it would shut off. After running nearly every diagnostic from the Bosch fuel injection troubleshooting guide, I tested the resistance on the magnetic pick up wire when the car was a no-start condition and found it had 0 ohms when it should have 700-800 ohms. Also tested from the negative pin to the distributor body which is suppose to give infinity ohms but it was 0 ohms too. I had a spare magnetic pickup so I took the distributor out, installed the new pickup ,gapped it, and re-timed the engine and ran the car through 3 fan cycles before I shut it off. Have driven it about 5 times since the repair and haven't seen the back of a flat bed soo... hope this advances the science for any 80-85 owners with hot start issues.

Side note: In the process of misdiagnosing, I replaced the most of the evap system (vapor canister, 3-way fuel vapor sepator, 2-way check valve underneath car), and the 2-pin connector and about 6 in. of wire going to the coolant temp sensor because I could change the RPM of the motor on cold start by moving the wires. Didn't fix my hot start problem but the idle seems a little smoother and more consistent.

[rridge]

Step one listed in the Bosch FI Troubleshooting guide is to check the ignition. It's seldom obvious whether a cranking no-start is FI or ignition related. The ignition side is much simpler to troubleshoot. The FI system depends on a reliable rpm signal from the ignition.

[spider2081]

Great that you car is up and running reliably.

I'm curious where you have the meter leads and what scale (range) the ohm meter was on when you made this test:

Also tested from the negative pin to the distributor body which is suppose to give infinity ohms but it was 0 ohms too