Fuel pumps

Tiny
RONNIEJD
  • MEMBER
  • 1991 FORD F-150
  • V8
  • 2WD
  • AUTOMATIC
  • 210,000 MILES
91 F150 fuel pumps won't turn on. Have changed the fuel pump relay, eec relay, fuse, and inersha switch with no luck. Any suggestions.
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Thursday, August 25th, 2011 AT 4:47 PM

12 Replies

Tiny
KHLOW2008
  • EXPERT
Have you tested for power supply to the relays?
Apart from parts replacement, what have you tested?
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Thursday, August 25th, 2011 AT 8:50 PM
Tiny
RONNIEJD
  • MEMBER
Have checked fire to eec relay, fuel pump relay, and fuel pump fuse all have fire. Checked fire at selector switch, one prong with low voltage. Inersha switch not triped.
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Thursday, August 25th, 2011 AT 9:07 PM
Tiny
RONNIEJD
  • MEMBER
Have tested both relay sockets, and they have fire. Checked the fuse socket, and it has fire. Checked selector switch which has low voltage on one terminal. Inersha switch not tripped.
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Thursday, August 25th, 2011 AT 9:11 PM
Tiny
KHLOW2008
  • EXPERT
At the self test output connector, does grounding the Light Blue/Orange wire works the fuel pump with ignition on?
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Thursday, August 25th, 2011 AT 9:22 PM
Tiny
CADIEMAN
  • MEMBER
Take the fuel pump pressure with a gauge. Also check the injector fuse.
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Thursday, August 25th, 2011 AT 10:18 PM
Tiny
RONNIEJD
  • MEMBER
Stuck screwdriver in self test connector on the light blue/orange wire and before I grounded it the pump started working. Does that mean a wire was loose in the self test output connector and should I change the self test output connector. Seems to be doing great now. Thanks for all your info and help.
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Thursday, August 25th, 2011 AT 11:20 PM
Tiny
KHLOW2008
  • EXPERT
That seems odd. The self test connector is connected to the fuel pump relay and ECM fuel pump grounding circuit. The only possibility for the problem would be a bad connection for the Light Blue/Orange wire which also leads to the ECM from there.

From back of self test connector, check the connection of the 2 Light Blue/Orange wires. It is not necessary to replace the connector, repairing their continuity should solve the problem.
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Friday, August 26th, 2011 AT 12:16 PM
Tiny
RONNIEJD
  • MEMBER
Truck started twice after it first started up. Test drove it about 3 miles. Turned it of. Now it won't start again. Tried to ground self test output connector. Nothing but fuel pump relay clicks and eec relay gets warm to touch.
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Friday, August 26th, 2011 AT 3:56 PM
Tiny
CADIEMAN
  • MEMBER
Ck the pump pressure!
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Saturday, August 27th, 2011 AT 1:41 AM
Tiny
KHLOW2008
  • EXPERT
After grounding the Self test connector, test for battery voltage at the fuel pump. If voltage is available, check the fuel pump grounding circuit.
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Saturday, August 27th, 2011 AT 11:50 AM
Tiny
RONNIEJD
  • MEMBER
No pressure at pump. Haven't checked voltage at fuel pump. Have temp. Changed the ECM module (5.8 lt.) With a 5.0 lt. EMC to check fuel pump. No change, doesn't work. Is the 5.0 compatible enough with the 5.8 to check the fuel pump?
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Thursday, September 1st, 2011 AT 8:39 PM
Tiny
CADIEMAN
  • MEMBER
Those are two different ecms no. Find the fuel pump fuse and test the voltage to the fuse. Then check the fuel pump for power and ground.
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Thursday, September 1st, 2011 AT 10:44 PM

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