Quote:
Originally Posted by rfmaster
In these early EFI systems GM put a primitive back to keep fuel pump operating by installing (normally open - NO) oil pressure switch in parrallel with FP relay contacts. If FP relay fails, but as long as oil pressure is above 4-6 PSI the oil pressure switch will keep current flowing to the fuel pump.
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You know it is a good day when you learn something new... this statement struck me as odd, so I looked at the circuit diagram and you are correct. It looks like the only real purpose of the FP relay is to prime the fuel system at start up before oil pressure builds. This also explains my weird fuel pump "run-on" problem I mentioned back in post #177 - the oil pressure switch is connected to BATT 12V+ (as is a good portion of the rest of the FP relay circuit) and provides power to the fuel pump after I turn the ignition off
until the pressure drops to the point where the oil pressure switch opens. Thanks for the education, RF... I just wish we could help find the problem for FB72.
Mark