DanD

Hi, yesterday,my 2000 4.0 stumbled a couple of times then stopped on the way to work.I was 30 miles from home,had no fuel pressure so I dropped the tank and put a new pump in.I still have no fuel pressure,and don't seem to have power to the FP relay,what could cause this? I can't find a schematic on my old haynes book or online.

any help would be greatly appreciated.

dcollins3208

Bad fuse, bad ground, bad relay, a short. I'd start with the fuse and go from there. My guess would be fuse or relay, more likely the relay.

dcollins3208

Here's a diagram from a 99

DanD

thanks for the diagram! I'll try swapping the ASD relay next I guess,I swapped the a/c clutch relay with the FP realy and still nothing,and my cheap multimeter that reads correct to the battery reads no power to the FP relay with the ign on.Also,I don't think it's normal for the cooling fan to kick on when you turn the key on,is it? starting to think it might be the PCM.

all the fuses in the power distribution center are good.

CCKen

Here's a diagram of the 2000/2001 fuel pump circuit.



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Here's the 2000/2001 PDC.




Here's the 2000/2001 JB.





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Here's a guide to the fuses in the PDC.



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DanD

thank you so much CCKen! that's more than enough for me to correctly diagnose what's going on! I sure appreciate your help.I was about to order a new pcm,this way I can make sure if that is indeed what it is.

DanD

well,the voltage to c1 reads 4 volts,I swapped the relays between the fp and starter,and starter still works.I have 12v to C5,unplugged the tank harness in case I got the wires wrong to the FP and the guage,reading 3 and 4v back there as well.I did notice when I was trying to determine which for sure was for the guage when I had it out in town,I couldn't get the guage to read anything but E under any circumstances,so that makes sense.

The fact I'm getting a funky voltage reading to the relay,and the cooling fan comes on whenever the ign is on,seems to point to the PCM.

What say you?

BTW,it has 200624 miles on it,so about time anyway from what I gather.

DanD

well,it's fixed.I checked the voltage to C1 on the FP relay,had only 4v.so I unplugged the PCM and it dropped to 0.I then checked continuity from the FP fuse to C1 and had continuity.

Somehow,I must have missed checking that fuse,or blew it while working on this in the near darkness in the gravel parking lot where I was dropping the tank and replacing the pump.

replaced the fuse,heard the FP and it starts now.I feel really stupid for missing that fuse,but not as stupid as I would have if I'd bought a new PCM and then found it.The fan is running b/c of a stuck relay.

Thanks for the diagrams! I sure made it a lot harder than it was,lol.