Hi Folks,

Been awhile since I've lurked around here. I have a head scratcher and am looking for some help. I have a 2006 F150 5.4 with a fuel pump that will not stop running. You read that right, the fuel pump won't stop. The truck runs fine. If I stop the engine for the day, the fuel pump will keep running until the battery runs down, and I have to jump it to get it running again. If I disconnect the battery when I'm done with it, and connect the battery back when I want to drive it, all is well. The thing is bone stock, no error codes, no other indication something is wrong. This one's a first for me. I've never heard of this before. I can't find any information about a fuel pump relay either. AFAIK, the PCM drives a relay that drives the pump, so that suggests I either have a pad PCM (ugh) or a bad relay. I'm hoping it's a stuck relay. My local dealership says it's the pump itself. that the relay is actually part of the fuel pump assembly. That doesn't make a ton of sense to me, but that ship has apparently sailed. Can anybody shed any light? Thanks.

 

Voltage is supplied to the fuel pump by the Fuel Pump Driver Module which is located on a crossmember above the spare tire. On these trucks they fail frequently, but the failure usually causes the pump to quit. I guess it could become shorted and supply voltage all the time, though I've never heard of that happening. I believe the FPDM is turned on and off by the PCM.

 

I would check the Fuel Pump Driver Module which is located on a crossmember above the spare tire. first it may be corroded and have holes in it cousin problems normally the fuel pump wont run but you never know

 

From what I can find, which is frustratingly little on this particular topic (and my manuals suck too), this FPDM gets it's power from the intertia switch, control signals from the PCM, and sends voltage to the pump. That means my dealership who told me the fuel pump relay is part of the pump itself, was full of crap. Another ford "expert" (not on this site) said the pump relay was getting stuck and staying on and that it can't be the PCM, is also full of crap. Done ranting. I'll have a look at that module today. What voltages should I be seeing? I know I should see battery voltage on the power lead, and I'm assuming same going out to the pump (upon signal from the PCM) what should I see coming from the PCM, is that a closure or battery voltage or something else? Thanks for your help!

 

I dont know the voltage but if unit in poor condition with pin holes or larger i would replace it