'74 2L Starts Then Dies, Never a convenient time... Options

[GregAmy]

Nice beautiful New England Day, heading off to the Manchester CT car show and...car won't start. Cranks, a few cylinders fire, then it dies. I cycle the key and hear the pump running and then stop (as before) and same thing: spits then dies.

I tried cycling the key a few times, with the mindset of building more pressure, and it spits a few more cylinders then dies. Even got it to rev a little bit with a half-dozen key cycles, but always dies.

Only other symptoms is that I noticed the last time I drove it earlier in the week it was dying when I put in the clutch. Was not consistent, only did ti a few times, but that was unusual behavior.

Stock 2L fuel injection, but with cold start and idle air bypass systems disabled; been running fine like this for the several years I've had it.

Checked all the relays, each works with the heater blower. Swapping them makes no difference (which I expected, given the pump cycles with the key). My guess is that however the pump is supposed to continue to run after releasing the key, it's not getting the power it needs (just a guess, I've not gotten under there with a voltmeter to verify). The wiring diagrams are not clear (to me) how that power is applied to the fuel pump relay.

Any way to quickly salvage my afternoon trip to the car show, or am I using my beautiful afternoon to swap the street car onto the lift for extended diagnosis?

40-yr-old electrics, gotta love 'em.

- GA

[Dave_Darling]

The only injectors I know of that are not electrical are MFI and CIS ones.

I don't believe there are any injectors that ground through the injector body. They all have a ground wire. Most injectors, in fact, have rubber holders that isolate them from the metal parts of the engine, so the body of the injector would be a lousy ground path anyway.

Most injectors are supplied a steady 12V (or less), and the ECU grounds the other pin of the injector to open it, and disconnects the ground to close the injector valve. D-jet is the main exception, as the injectors are always grounded and the ECU sends power to the other pin of the injector to open it and disconnects the power to close it.

The ground for the injectors is the same as the ground for the FI. It is a ring with three tabs on the case seam on top of the engine near the flywheel end. The ring goes under one of the case through-bolts. Always worth checking these grounds.


I will want to know what the fuel pressure is when the car does not start. Doesn't matter if it's 29 PSI when the engine is running, because the problem isn't occurring then.

--DD

[McLovin]

The only injectors I know of that are not electrical are MFI and CIS ones.

I don't believe there are any injectors that ground through the injector body. They all have a ground wire. Most injectors, in fact, have rubber holders that isolate them from the metal parts of the engine, so the body of the injector would be a lousy ground path anyway.

Most injectors are supplied a steady 12V (or less), and the ECU grounds the other pin of the injector to open it, and disconnects the ground to close the injector valve. D-jet is the main exception, as the injectors are always grounded and the ECU sends power to the other pin of the injector to open it and disconnects the power to close it.

The ground for the injectors is the same as the ground for the FI. It is a ring with three tabs on the case seam on top of the engine near the flywheel end. The ring goes under one of the case through-bolts. Always worth checking these grounds.


I will want to know what the fuel pressure is when the car does not start. Doesn't matter if it's 29 PSI when the engine is running, because the problem isn't occurring then.

--DD

Interesting stuff. So he needs to check the ground and maybe the wires themselves for cracks or partial breaks.