fuel pump

10

Asked by GuruDJTFZ Oct 01, 2017 at 01:21 PM about the 1990 Ford F-150 XLT Lariat LB

Question type: Maintenance & Repair

1990 f150. Put a new fuel pump in and it worked
fine. Shortly after it stopped. What can cause this?
Tested the pump and worked. New relay and
ignition switch. Pump still dont come on when you
turn the key.

4 Answers

10

No power going to the pump. I have checked wires and havent found any problems. Can the ignition module on the distributor have anything to do with it?

1 people found this helpful.
58,955

First check the fuse (I think it may be under the hood) then the relay. If these check out, there is an impact switch (inertia switch, some people bypass it) that cuts off the fuel pump in a roll over or high impact. It is in different locations,... frame, under floor mat, Etc (likely under the dash and can go bad.) Possibly computer stopped sending a ground signal to the pump relay. I would test relay first (remove it as may have corrosion on the relay pins), then inertia switch (think under dash on most) then for voltage out of pin (forget which pin) for fuel pump at computer. If its dual tanks may be a failing fuel tank selector switch (known for melting the switch wiring on the back of the switch itself). Did you have any codes set on the computer? Can use jumper wire to ground the relay to battery - terminal see if it clicks if so leave grounded and see if voltage appears at the inertia switch (use to be the brown wire I think for power to inertia switch may be wrong tho.) Otherwise somewhere along the wiring is a fuse link to check and the possible bad wire going from from inertia or tank selector switches threw floor to tanks that may have gotten bad.

3 people found this helpful.

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