question about fuel pump voltage
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question about fuel pump voltage
I have an '05 e250 with a crank no start. Fuel pump is not turning on. The fuse, relay and inertia switch all check out.
With the harness unplugged at the pump, turn key on, I get 12.5v at the hot wire. The ground wire has 8v with the key on, is this right?? why would the ground wire have voltage at this plug?
When I plug the pump in I am only getting 3v on the + side, and 0.1v on the ground
With the harness unplugged at the pump, turn key on, I get 12.5v at the hot wire. The ground wire has 8v with the key on, is this right?? why would the ground wire have voltage at this plug?
When I plug the pump in I am only getting 3v on the + side, and 0.1v on the ground
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From: Virginia
All I have is a 2003 diagram. In it, I see nothing unusual about the wiring. In 2003 they come out of the underhood fuse box with a 30 amp fuse #17. This goes to the fuel pump relay located in the same underhood fuse box. It then leads from there to the inertia switch (safety crash switch) and then back to the fuel pump.
See if you can find the fuel pump relay. I would probe in there for voltages, possibly you can find another relay that is the same type of less importance, like the WOT A/C relay or something like that, and swap the relays and see if that makes a difference.
See if you can find the fuel pump relay. I would probe in there for voltages, possibly you can find another relay that is the same type of less importance, like the WOT A/C relay or something like that, and swap the relays and see if that makes a difference.
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All I have is a 2003 diagram. In it, I see nothing unusual about the wiring. In 2003 they come out of the underhood fuse box with a 30 amp fuse #17. This goes to the fuel pump relay located in the same underhood fuse box. It then leads from there to the inertia switch (safety crash switch) and then back to the fuel pump.
See if you can find the fuel pump relay. I would probe in there for voltages, possibly you can find another relay that is the same type of less importance, like the WOT A/C relay or something like that, and swap the relays and see if that makes a difference.
See if you can find the fuel pump relay. I would probe in there for voltages, possibly you can find another relay that is the same type of less importance, like the WOT A/C relay or something like that, and swap the relays and see if that makes a difference.
I'm at the point of assuming its a ground problem but trying to locate it will take some time.
Ground wires in any circuit should only have a very small voltage, around 0.1 - 0.2volts correct? I am getting 8volts at my ground wire in the fuel pump circuit ( this is when the fuel pump is UNplugged)
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Yes it does and mine had typical corrosion so I replaced it with a new one
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From: St Louis
The 2003 diagram isn't useful, generational wiring update, completely different.
Did you check the integrity of the ground going TO the FPDM? Pin 3, BK/OR wire. Should be connected to a grounding bolt on the inside of the LH frame rail aft of the axle.
If that ground is good, then the replacement FPDM becomes suspect. What part was used?
Yes it does and mine had typical corrosion so I replaced it with a new one.
If that ground is good, then the replacement FPDM becomes suspect. What part was used?
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The 2003 diagram isn't useful, generational wiring update, completely different.
Did you check the integrity of the ground going TO the FPDM? Pin 3, BK/OR wire. Should be connected to a grounding bolt on the inside of the LH frame rail aft of the axle.
If that ground is good, then the replacement FPDM becomes suspect. What part was used?
Did you check the integrity of the ground going TO the FPDM? Pin 3, BK/OR wire. Should be connected to a grounding bolt on the inside of the LH frame rail aft of the axle.
If that ground is good, then the replacement FPDM becomes suspect. What part was used?
Hotshot
Joined: Jan 2004
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From: St Louis
Ive tried bypassing the FPDM with a jumper from pin 2 to 3 and 4 to 5 with no luck.
1. Testing procedural error. Pin 5 is HOT only when the fuel pump relay is energized. Verify input power. Verify it it UNDER LOAD as you could have a high resistance that is causing the supplied voltage to be dropped before it ever gets to the pump.
2. Open ground circuit as already described.
3. Both of the above.
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From: Virginia
I am getting way behind the times. I looked at the above diagram, and then did a google search on "what is the purpose for Ford's fuel pump driver module" but I did not get all the info that I wanted. They say they are now varying the voltage of the fuel pump, and that varies the output of the pump. And from the above diagram, it looks like the engine computer has control wires going to the module.
But my questions are why did they go to this setup? Before they ran the fuel pump wide open, and the regulator on the fuel rail kept track of things, dumping most of the fuel back to the tank when it wasn't needed. Did they get rid of the fuel regulator? Do they still have a return line to the tank? What is the main advantage to this way of doing it? I am assuming the other OEM's are doing the same thing. Seems like they all go to the same engineering schools and think the same way.
But my questions are why did they go to this setup? Before they ran the fuel pump wide open, and the regulator on the fuel rail kept track of things, dumping most of the fuel back to the tank when it wasn't needed. Did they get rid of the fuel regulator? Do they still have a return line to the tank? What is the main advantage to this way of doing it? I am assuming the other OEM's are doing the same thing. Seems like they all go to the same engineering schools and think the same way.
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Thanks for the help I got it running, I found a broken ground cable that grounds the body to the frame, the braided one on the passenger side.. Very surprised this affected my fuel circuit, new cable and it started right up.
Thread Starter
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New User
Joined: Oct 2019
Posts: 10
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I am getting way behind the times. I looked at the above diagram, and then did a google search on "what is the purpose for Ford's fuel pump driver module" but I did not get all the info that I wanted. They say they are now varying the voltage of the fuel pump, and that varies the output of the pump. And from the above diagram, it looks like the engine computer has control wires going to the module.
But my questions are why did they go to this setup? Before they ran the fuel pump wide open, and the regulator on the fuel rail kept track of things, dumping most of the fuel back to the tank when it wasn't needed. Did they get rid of the fuel regulator? Do they still have a return line to the tank? What is the main advantage to this way of doing it? I am assuming the other OEM's are doing the same thing. Seems like they all go to the same engineering schools and think the same way.
But my questions are why did they go to this setup? Before they ran the fuel pump wide open, and the regulator on the fuel rail kept track of things, dumping most of the fuel back to the tank when it wasn't needed. Did they get rid of the fuel regulator? Do they still have a return line to the tank? What is the main advantage to this way of doing it? I am assuming the other OEM's are doing the same thing. Seems like they all go to the same engineering schools and think the same way.
Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
I guess "Minimum 1 pint in 30 seconds" into an old coffee can won't cut it anymore?