Chevrolet Repair: Wont Start - Fuel Injectors Signal, oil pressure switch, crankshaft position sensor

Question
1988 350 TBI K1500. I have tested my fuel pressure & it is within specs (9-13 psi) with fuel pump running but get no spray from injectors. I can pour a small amount of fuel into the throttle body and the engine will start and run momentarily. I have used a 9-volt battery on the injector with the fuel pump running (with jumper in ALDL) and gotten spray from the injector. +12 volts is present at the injector connector with the key in the run position but apparently the negative signal is not getting switched to ground while trying to start. I replaced the computer (and used the original PROM and CALPAC) with the same results. What other solutions could I be overlooking? Are there any sensors that would prevent the computer from switching the injector signal to ground?

Answer
Hello Kyle,
I believe the crankshaft position sensor sends the signal to operate the injectors, as well as the fuel pump relay.
You could check the relay to see if it is operating properly. Does it re-energize during cranking after the orriginal three second prime operation?
Don't check at the wire feeding the fuel pump, because there is an oil pressure switch that sends battery voltage to the pump as soon as oil pressure reaches 4PSI, so you would be measuring that voltage. You need to just check the relay operating wire, or just feel if the relay closes.

But the crank sensor, or its wires is what I suspect.

Van