Please help
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6th Gear
Joined: Jul 2025
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Please help
I have a 95 F150 with the 351W, I am getting a bad misfire when the engine is at operating temp and only at idle. I replaced plugs wires distributor cap and rotor. That didn’t fix the issue with the misfire. I then moved on to the fuel system, I did a pressure test on the fuel rail and got 29 psi while running, with no loss of pressure with the engine off. I replaced the front tank and fuel pump. Now that the new tank and pump is in it won’t start or run. But it will start and run on the rear tank with the old pump. I have checked and double checked the wiring, pump (to make sure it is a working pump) and all of the grounds, the new pump is loosing voltage, it starts with 12v immediately after the ignition is turned on but will drop to 6.5v after about a second. I tested the fuel selector switch and found that 1 of the terminals for the front tank was bad. replaced the fuel selector switch and checked what I could see of the wiring for that. Checked all of the relays by switching them around and with a multi meter (all of them are working). I have even checked to make sure the inertia switch wasn’t tripped. I’m now stuck trying to figure this out.
Thread Starter
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6th Gear
Joined: Jul 2025
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just did the pressure test. It is 0 psi. And the rear is at 27psi while running. thank you for saying that, I was so caught up in all of the what if’s that I didn’t even think to do that simple test.
FTE Chapter Leader
Joined: May 2006
Posts: 12,342
Likes: 1,315
From: Central Mississippi
Filter changed?
You know about the 1-2 second prime that happens at Key On-but not start?
The ECU won't give the pumps power unless it sees distributor turning.
Testing a pump in place can be done with a drill battery & some jumper wires.
Just don't run for long
What did the sock look like?
You know about the 1-2 second prime that happens at Key On-but not start?
The ECU won't give the pumps power unless it sees distributor turning.
Testing a pump in place can be done with a drill battery & some jumper wires.
Just don't run for long
What did the sock look like?
Thread Starter
|
6th Gear
Joined: Jul 2025
Posts: 6
Likes: 0
Filter changed?
You know about the 1-2 second prime that happens at Key On-but not start?
The ECU won't give the pumps power unless it sees distributor turning.
Testing a pump in place can be done with a drill battery & some jumper wires.
Just don't run for long
What did the sock look like?
You know about the 1-2 second prime that happens at Key On-but not start?
The ECU won't give the pumps power unless it sees distributor turning.
Testing a pump in place can be done with a drill battery & some jumper wires.
Just don't run for long
What did the sock look like?
Lead Driver
Joined: Feb 2002
Posts: 7,966
Likes: 595
From: Greater Austin, Texas
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Thread Starter
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6th Gear
Joined: Jul 2025
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I know, I am trying to fix it on a budget and do the rear pump later.
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FTE Chapter Leader
Joined: May 2006
Posts: 12,342
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From: Central Mississippi
Well, if it were mine, I'd put a meter on the incoming harness plug & see if I get acceptable voltage at KOEO prime.
If yes, I'd put my drill bat on the harness pins that I know go to pump motor & verify it doesn't run before dropping the tank again..
Did your replacement pump require harness/plug splicing to match existing?
If yes, I'd put my drill bat on the harness pins that I know go to pump motor & verify it doesn't run before dropping the tank again..
Did your replacement pump require harness/plug splicing to match existing?
Thread Starter
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6th Gear
Joined: Jul 2025
Posts: 6
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Well, if it were mine, I'd put a meter on the incoming harness plug & see if I get acceptable voltage at KOEO prime.
If yes, I'd put my drill bat on the harness pins that I know go to pump motor & verify it doesn't run before dropping the tank again..
Did your replacement pump require harness/plug splicing to match existing?
If yes, I'd put my drill bat on the harness pins that I know go to pump motor & verify it doesn't run before dropping the tank again..
Did your replacement pump require harness/plug splicing to match existing?
Hotshot
Joined: Jul 2020
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From: Near Salt Lake City
Replace the caps in your processor is what I'd do next
Hotshot
Joined: Jun 2015
Posts: 12,871
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From post 1
FTE Chapter Leader
Joined: May 2006
Posts: 12,342
Likes: 1,315
From: Central Mississippi
Judging from posts over the years, the most common failures on new module installs are with the spliced in connectors.
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