1992 Ford F-150 - Fuel pump question

key on engine off fuel pump wont cut off

Possibly the contact points inside the fuel pump relay are stuck together or the blue/orange wire (which is the ground for the pump relay trigger circuit through the ECM is still showing a ground after the key is first turned to the run position.

That blue/orange wire should ground in the ECM for 2 seconds before going away IF the engine is not cranked over.
This could be checked with an ohmmeter or test light connected to the battery +.


OK correct above, the fuel pump power circuit is purposely designed to turn off by the powertrain computer, anytime the computer detect the engine isn’t rotating. Often involves monitoring for pulses in the ignition circuit. That’s done for safety reasons, so the FP turns off in event of a crash. I’d guess however that the engine computer in OP’s case knows the engine isn’t rotating, and the problem is past that point in the circuit; i.e. either the fuel pump relay contacts are stuck, or there’s a short circuit, possibly inside the relay plate that is bypassing the relay.

I had a VW Rabbit years ago with this problem, turned out to be a faulty fuel pump relay. When I showed this problem to a VW Dealership shop who had made a mistake that damaged the relay, they told me the fuel pump is supposed to run whenever the key in in “on” … lol …