Scratching my head over this one... 87 305 TPI, turning on the ignition does not turn the fuel pump on. The fuel pump is good, if I run power directly to it it works fine but does not receive power via the usual path. I'm pretty sure the fuel pump relay is not the cause of the problem, as pulling it out and jumping the live wire to the pump power wire also does not work. There is definitely power coming to the live wire just not going out the other way.

I don't know if this is related, but when I short the live wire to the pump power on the plug, the MAF sensor relay clicks on and off if the ignition is off, or clicks on and stays on if the ignition is turned on.

This is especially frustrating because it worked fine until yesterday when I replaced the spark plugs... best I can figure I bumped something while getting those hard to reach ones at the back. Any help would be much appreciated.

 

Be careful when jumping relay connections, you can damage the ECM.

Because the pump does not come on when you jump power to the pump wire in the socket, assuming you’re jumping the correct one, that places your problem between the socket and the pump, an open circuit.

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Happy Racing!

 

Well after much agonizing troubleshooting, I tracked the problem down to one of the grounds. It was good enough to let the pump run with 12v applied directly but bad enough that it wouldn't work through the wiring. Go figure...