Fuel pump relay

Asked by Jul 19, 2017 at 11:02 AM about the 2004 Ford F-150 FX4 Ext. Cab 4WD

Question type: Maintenance & Repair

I believe my fuel pump relay is bad. Truck will crank
but won't start. Cannot hear pump running. I ran
power to the fuel pump and got it started so I
believe it's the fuel relay. I'm seeing that some
people are saying this year truck the fuel relay
switch is soldered into the fuse box and isn't
interchangeable. Is this true? Do I have any other
options than buying a new fuse box? New fuse box
costs 400 from the dealer

8 Answers


At the relay, unplug it, is terminal 30 hot, with engine cranking, It should be. If so, you can use jumper wire between terminal 30 and terminal 87, the fuel pump should run. If it runs that usually means the problem is on control side of relay, voltage and ground. The two top wires in diagram are voltage and both fuse protected. The voltage comes from pcm power relay. I'd want to check voltage and ground circuits for the relay before replacing. Just my opinion.

3 people found this helpful.

The 2004 relay is hard wired into the fuse box. So I cannot take it out. I spoke to another person who told me that if I have power on 32,33,34 with the key on, then my relay should be fine....I've changed the driver module and couldn't get it to start. I put power to the pump and got it to start. Cannot figure out what the issue is..

By the way I did have power to the 32,33,34


To start off with *WHITE3281* did not initially indicate what year his 150 was ? I have a 2002 model that began cranking and not starting on occasion and most recently will not start - it has no fuel pressure, relays K4 (fuel pump) and K163 PCM bench check O.K. and operate O.K. Both have power at pins 30 even with the key turned off - It is indicated elswhere that the wiring schematics are the same for the 1997/2003 models however the parts involved are physically located in different locations and are identified differently - On mine they are located in the fuse/relay box on the front LH fender - while *oilyspill*does give a great picture of the individual relay diagram - and guides one on how to jump directly to the pump --- I need a schematic that shows the whole fuel pump wiring system for a 2002 so I can see what else might be in the system --- For safety reasons I would suggest using an ohmeter to check the fuel pump for ohms /and or shorts before throwing any unfused voltage at it ---


ref." old guy " evidently I'm in exactly the same boat as you - I did exactly that and the ohms were well over 22k - then I hit it with 12 v. - obviously the pump still would not run - I did this @ the relay base - beforehand I field checked the relay and it worked just fine - remember even doing this there still is the possibility of corrosion buildup on either the hot side or the ground side so nothing is really accomplished here other than finding out if your circuit opened or not - Now I need to find someone younger than me to get er done ! Yes it would be nice to find a nice clearly legible electrical schematic of this circuit (Not a diagram)

1 people found this helpful.

2002 ford f150 fuel pump electrical schematic

3 people found this helpful.

mine do the same thing 2004 f150 my PCM relay switch was loose push back in started right up i might need to buy a new relay fuse box new for $400 .


ref: White 3281,oldeguy,oilyspill et all - These are all familiar posts for me and all have good information - my 2002 has done the same recently - FYI - In checking these things note there is a pressure relief valve on the back of fuel rail on my 4.6 L - it looks similar to a tire valve stem and can carefully be depressed to check for fuel pressure shortly after cranking - also on some year ? models there is an emergency crash switch located behind and above the RH passenger kick panel that sometimes trips if one gets bumped ! In checking my problem further I find my fuel pump circuit has 2.67K ohms resistance ( relay base to ground )and I'm on here trying to find out what is an acceptable reading ? - I suspect it should be less than 50 ohms ? Digging into this more I find that one of my fuel tank straps has let go and maybe with the tank hanging down a bit it has pulled a connection loose ?? 65 years ago it was a lot easier for me to crawl under vehicles and work on them !! Also FYI - I now find that on the subject of the fuel tank straps Ford had a Safety Recall Notice on them for some of the earlier models ( 2004 and older I believe ) -------- from 07/29/2011 they issued Safety Recall # 11V385000 & listed as Campaign # 11S21 -------- Has yours been done yet ? Cheers " another old guy "

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