87 f150 fuel pump problem
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87 f150 fuel pump problem
87 f150 4.9L 300 straight 6 with dual center tank. (17gal & 19gal). the fuel pump is not running and i've discovered i have continuity across all 4 pins of the plug at the fuel pump with it unplugged from the pump. this is the pump in the tank. the high pressure pump has been replaced along with the EIM on the distributor, the fuel pump relay, and fuel pressure regulator. is there any other componant involved that could be giving me these readings or is it just a bad wire(s)? i've traced the wires coming out of the pump all the way up to the cluster at the firewall. i haven't veiwed every inch of each wire but they seem solid and i can watch each wire move at another location as i move it. wasn't sure if there was another electronic device responsible for sending signals back to the pump. thanks for any and all input
Elder User
Joined: Sep 2003
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From: Louisiana
Your tank selector switch is in the circuit. Most likely you pump is bad. Does the guage work? The fuel pump is a common failure on Fords. Not each individual truck but within the Ford Truck Community.
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yes the guage works for both tanks which i don't understand beings how when the plug at the tank is disconnected from the pump i have continuity across the pos and neg for the pump and the guage so how the guage is working i have no clue. the fuel pump in the tank and on the rail have both been replaced. how is the selector switch wired in relationship to the pump?
thanks alot
thanks alot
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From: Louisiana
https://www.ford-trucks.com/forums/s...d.php?t=476082
Read this thread. Subford put a schematic there that covers your year. Hope it helps.
Read this thread. Subford put a schematic there that covers your year. Hope it helps.
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the white button on the top is not popped and just to be sure i unplugged it and jumpered the plug. also i was under the assumption there was one pump in the tank however it seems as though i have two pumps in the tank. i haven't physically looked yet but thats what the wiring diagram says. that being the case, i would be experiencing this on the pump in the center of the tank. haven't had time yet to look for another pump to determine whether its the front or the rear. thanks
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From: Louisiana
Originally Posted by JunkHead73
also i was under the assumption there was one pump in the tank however it seems as though i have two pumps in the tank. i haven't physically looked yet but thats what the wiring diagram says. that being the case, i would be experiencing this on the pump in the center of the tank. haven't had time yet to look for another pump to determine whether its the front or the rear. thanks
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ok i don't know who's dumber, the guy who tried to explain how one pump works two tanks,or how two pumps are in one tank, or me for believing any of it. anyway... i have 2 individual tanks. really feel like a moron now. i have continuity across all four pins of the front tank pump plug. i disconnected the fuel tank selector switch on the dash, it checks ok and i have continuity across four of the six pins on that plug. all waires look fine and i can't find a flaw in any of them. going crazy.......................
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From: Central NY
You have a low pressure fuel pump in each tank (so thats 2 so far) and a sigle hi pressure pump inside the frame rail. (3 total pumps for your year)
The selector switch simply directs power to the selected in-tank pump.
The hi pressure pump and the selector switch both get power from the fuel pump relay thru the inertia switch.
Check for 12v at the inertia switch. If you don't have it there check for it on the yellow wire on the fuel pump relay. If you dont have it there check fusable link M and if thats good check the solenoid.
If you have 12 on the yellow wire at the FP relay, check the eec relay.
Hope this helped,
Tim
The selector switch simply directs power to the selected in-tank pump.
The hi pressure pump and the selector switch both get power from the fuel pump relay thru the inertia switch.
Check for 12v at the inertia switch. If you don't have it there check for it on the yellow wire on the fuel pump relay. If you dont have it there check fusable link M and if thats good check the solenoid.
If you have 12 on the yellow wire at the FP relay, check the eec relay.
Hope this helped,
Tim
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