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91 pk with no power to the fuel pump


jasont26
01-15-2008, 11:46 AM
i have a 91 chevy 6 cylinder with no power to the fuel pump i checked the fuse and relay and both are good. If i jumper the relay to start it, it will stay running when i pull the jumper but will not start. I need to know what controles the fule pump relay

J-Ri
01-15-2008, 04:27 PM
There is an input to the relay from the PCM. The PCM will supply either power or ground, I can't remember for sure which. Check for voltage/ground with a voltmeter. A test light will draw more current than the circuit is designed for.

jasont26
01-15-2008, 04:42 PM
i did use a test light and found no voltage there from the pcm. I will re check it with a dvm, do you think i did any damage??

J-Ri
01-15-2008, 04:46 PM
It's possible... probably not likely for just a short test period, It's just better to be safe. A relay has about 80 ohms resistance, a test light has around 3 ohms. And if it isn't supplying power, there was no harm done.

jasont26
01-15-2008, 04:53 PM
so with no power there am i looking at a new pcm??

J-Ri
01-16-2008, 05:05 PM
Not necessarily. First, check for power to the wire off the PCM, there could be an open in the wire somewhere. Also, make sure you have power to the PCM from the ignition switch. You probably do if it runs jumpered, but I try to check everything I can.

jasont26
01-23-2008, 12:15 PM
just a update i changed the oil pressure sending unit and it runs without the jumper but it starts hard and i dont hear the fuel pump prime. i found a wireing diagram and there is a few places the power comes from for the fule pump relay. the hot fuel modual and the fule primer module i need to find them and check them. thanks for the help

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