Fuel Injection: no negative reading at injectors, Car dies after 2-3 seconds Options

[Stanley1x]

My mechanic states he does not get negative at the fuel injectors (1974 1.8) and the car starts and runs only a couple seconds via the cold start plug.

Any suggestions as to why or where to to locate the problem would be greatly appreciated! Thank you

[timothy_nd28]

I do agree with finding a new mechanic that's competent with this fuel injection system, otherwise he will burn you by randomly replacing parts on your nickle.
Also to reiterate what was said, Ljet fuel injection systems do not have a separate fuel injector trigger points inside the distributor like the Djets have. Ljets do instead make tandem use of the ignition points inside the distributor as a trigger to batch fire the injectors via the ECU. The ignition point generates a frequency with tons of ringing and voltages up to 400volts that is dependent on engine rpm. The Ljet ECU listens to this noisy signal (on the negative terminal of the ignition coil) and then condition this noise by filtering and shaping the waveform so that it could be used by the semiconductor circuitry inside the ECU. I have built a similar circuit for my LED controller, which also listens to this noisy signal.

I still think your problem is related to the fuel delivery system. I have seen some (more than one) Ljets where the car will still run with the air flow meter connector unplugged. With that said, these cars ran horribly and the dual relay was bypassed so that the fuel pump could not be interrupted.

I would recommend installing a fuel pressure meter on the fuel rail. Have someone start the car while you or your new mechanic monitors the fuel pressure. As you are starting the car, you should be slightly above 30psi on the meter. Keep watching the meter as the car begins to stall. It should still be holding rock hard 30 psi. If you witness 30 psi as you are cranking, but the pressure drops after it starts, I would then temporarily add a jumper wire from pin 88d of the dual relay (black wire with red stripe) to the positive battery post. Try starting the car again, if the car stays running, you have isolated the problem to either the dual relay or the fuel pump contacts inside the airflow meter, or the wiring harness or a vacuum leak. I have seen a crack in the rubber S boot which was large enough to cause not enough low pressure to pull the airflow meter flap which in turn engages the fuel pump contacts at idle.