Mechanics

F150 LOW VOLTAGE AT FUEL PUMP

1999 Ford F-150

Engine Performance problem
1999 Ford F150 V8 Four Wheel Drive Automatic 130000 miles

changed bad alternator now fuel pump wont run. Checking 7.3 volts at fuel pump connection. Checking 7.3 volts at the emergency shut off switch. Battery is fully charged. Replaced fuel pump also. Changed relay also. Where is fuel pressure regulator located, could it be the problem
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Jadams6831
May 23, 2010.




Hi jadams6831,

Thank you for the donation.

No, it is not a problem with the fuel pressure regulator if the fuel pump is not running.

The voltage should be battery voltage at the fuel pump and since you are only getting 7.3 volts, something is wrong somewhere.

Is your engine 4.0, 4.6 or 5.4 L?
Did you test the voltage at the fuel pump relay?

KHLow2008
May 24, 2010.
Hadnt gotten that far yet. Did swap out relay though, it didnt change anything. Cant figure out why changing alt caused this or coisadence.

Tiny
Jadams6831
May 24, 2010.
I need to know the engine specs to get the correct wiring diagrams

KHLow2008
May 24, 2010.
Sorry. Its a 5.4l extended cab xlt 150

Tiny
Jadams6831
May 24, 2010.
The fuel pump relay gets it power from Fuse # 10 ( 20 A) ( Light Blue/Orange wire). Check if you have 12 volts to the fuel pump relay via this wire ( terminal # 30 of relay ).

Remove fuel pump relay and apply battery voltage to terminal # 87 of fuel pump relay and check if the fuel pump works.

Under right side of dash there is an inertia fuel shut off switch. Check for continuity between th eDark Green/Yellow and Pink/Black terminals.
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KHLow2008
May 25, 2010.
Thanks for your assistance I think I can get it from here. Jadams6831

Tiny
Jadams6831
May 25, 2010.
You're welcome and if you have anything more, just post reply and I will get back to you once I am online.

Thank you for using 2carpros and have a nice day.

KHLow2008
May 26, 2010.
We found a bad tang on fuel pump fuse. Of coarse fuse checked good but thats what happens when you assume. Thanks for your help

Tiny
Jadams6831
May 26, 2010.
Glad you have fixed the problem.

Have a nice day.

KHLow2008
May 27, 2010.

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