'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

[GregAmy]

Ok, yeah, this thing is really pissing me off now.

- Car won't start. Turn on key, hear pump. Cranks, brief fire, then dead cranking. I smell fuel.
- OK, maybe fuel pump isn't staying on during crank, so I jump the relay, pin 87 directly to battery. Pump on, hear fuel sloshing through the return.
- Cranks, brief fire, then dead cranking.
- I remove each electrical connections I can get to easily, one-by-one: TPS, temp sensor, both large connectors to the relay plate, each relay individually. Try cranking after each: Cranks, brief fire, then dead cranking.
- After doing each one-by-one, ensure terminals are clean, wipe with dieletric, ensure proper secure connection, try cranking after each: Cranks, brief fire, then dead cranking.
- I ask my wife to briefly join me in the garage, sit her in the driver's seat, ask her to try and start it. Cranks, brief fire, then dead cranking.
- I ask her to try again, but this time I remove the air cleaner and snag some brake cleaner to spray into the throttle body as she tries to start:

Cranks, fires, then runs.

I keep it running by hand (as well as one can do without an AAR) and the engine continues to run after I stop spraying brake cleaner in the TB. I keep it running until it warms up, and ask her to turn it off, and retry.

It starts and runs.

I just took it for a ride around the neighborhood, starts and idles fine (it's warmed up now). I get home, shut it off, it restarts and runs.

I have no idea what is wrong with this thing.