90 F150 Fuel Pump Issue
12-23-2014, 11:04 AM
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90 F150 Fuel Pump Issue
OK guys. I owe a case of beer to whoever can help me out of this jam. I'm in the middle of moving into a new house and my truck is stuck at my old house. 
Anyway. My issue is this. The fuel pumps will not run when i turn on the key. (dual tanks and neither will work)
A few weeks ago i had an intermittent issue with the fuel pumps staying on after i shut off the truck. get out and bang on the relays and they would shut off. so fast forward to the day i closed on my house with a bed full of furniture. hit the key truck turns over and no fuel pump prime. So far i have changed:
Fuel pump relay
EEC relay
swapped the EEC with another i had.
I've tried to jump the relay and still no fuel pump power.
I've test power at the relay plug and i have power at the yellow wires and at the red.
I do NOT have power at the wires going into the inertia switch.
I also only have a little bit of power on one connector on the dash switch.
I'm very good mechanically, but electrically i'm a freakin idiot. the two guys i know that could help me out are both busy and again i'm stuck. i need to move my truck this week to my new house. does anyone have any suggestions. i don't want to keep throwing parts are this. i also can't understand why there is no power going into the inirtia switch. gotta be a bad wire near the relays i'm guessing, but i checked and i have power on both sides on the fuesable links as well. any insight would be GREATLY appreciated. Thank you in advance. P.S. i DID use the search function and have tried the test that many people have mentioned. My next step was going to be replacing the fuel pump relay wiring harness and EEC wiring harness, but i wanted to see if anyone else had any ideas b/c i'm running out of them.
Anyway. My issue is this. The fuel pumps will not run when i turn on the key. (dual tanks and neither will work)
A few weeks ago i had an intermittent issue with the fuel pumps staying on after i shut off the truck. get out and bang on the relays and they would shut off. so fast forward to the day i closed on my house with a bed full of furniture. hit the key truck turns over and no fuel pump prime. So far i have changed:
Fuel pump relay
EEC relay
swapped the EEC with another i had.
I've tried to jump the relay and still no fuel pump power.
I've test power at the relay plug and i have power at the yellow wires and at the red.
I do NOT have power at the wires going into the inertia switch.
I also only have a little bit of power on one connector on the dash switch.
I'm very good mechanically, but electrically i'm a freakin idiot. the two guys i know that could help me out are both busy and again i'm stuck. i need to move my truck this week to my new house. does anyone have any suggestions. i don't want to keep throwing parts are this. i also can't understand why there is no power going into the inirtia switch. gotta be a bad wire near the relays i'm guessing, but i checked and i have power on both sides on the fuesable links as well. any insight would be GREATLY appreciated. Thank you in advance. P.S. i DID use the search function and have tried the test that many people have mentioned. My next step was going to be replacing the fuel pump relay wiring harness and EEC wiring harness, but i wanted to see if anyone else had any ideas b/c i'm running out of them.
12-24-2014, 06:51 PM
#3
Sometimes.....the wire connector under the relay goes bad. If you unclip the relay box from it's holder, you can turn it upside down, take the bottom of the relay box off and check the wires coming out of the relay.
It's worth a look because they do get corroded.
You don't say if you have dual tanks but the dash switch on those can act up. I'm just thinking relay box first because you said banging on it helps.
Also check just call me sean's post at the top of the page on checking codes. The pic with green arrows shows how to test the pumps.
It's worth a look because they do get corroded.
You don't say if you have dual tanks but the dash switch on those can act up. I'm just thinking relay box first because you said banging on it helps.
Also check just call me sean's post at the top of the page on checking codes. The pic with green arrows shows how to test the pumps.
12-29-2014, 07:40 AM
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Well just a quick update. Bought a new FP Relay connector and rewired it up. Truck fired right up. I guess it had a bad connection at the plug? Either way it's back up and running now. 