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Fuel pump won't turn off?

J. Alexander
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J. Alexander New Member

J. Alexander

Posted
Posted

Hi, just got my hands on a 2007 silverado 1500 classic with 4.3 last week, now I'm having an issue. Truck runs fine, but when I turn off the ignition and remove the key, the fuel pump is still running. I thought maybe it would turn off so I went about my business, eventually drained my battery. Got the battery charged and going again, but fuel pump still on after shutting engine off. If I go to the fuse box under the hood and remove either the fuel pump relay, or the PCMB relay, it shuts off. I've tried tapping the relay to see if it's stuck, nothing. I've tried swapping an exact relay to the fuel relay, still on. I read that the oil pressure sensor could cause it to run, so I slid the distributor cap to the side and unplugged the connection on the sensor, the fuel pump still runs. Am I overlooking something obvious? Please help!

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

sounds like a bad pcm but before you condemn it I would get a wiring diagram and check the ground and power inputs to the pcm and the fp relay signal. today I had an 05 Sierra 6.0 that wouldn't stay running after a battery swap, no gauges, radio and blower wouldn't shut off even with the key out and no communication to the scan tool even though it booted up  I pulled the battery back out to see if the guy who did the swap messed up the ground and everything checked out but corrosion on the negative terminal. cleaned that up, touched the cables together to clear the capacitors in the pcm/bcm  and problem solved. it didn't seem to be a bad ground as it passed a voltage drop test to the body and cranked over fine so I'm thinking some how 1 of the modules had gremlins. I would look and make sure no 1 has messed with the wiring or added anything aftermarket that could be causing the problem and try doing the battery cable thing for the hell of it then break out the wiring diagram if it still does it

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