Read posts 8 and 18. I believe it's either a short in the fuel pump wiring between the relay and the inertia switch, or possibly a PCM problem in light of post 18.
Fuel Pump Fuse Blows
- Thread starter Rickyll7
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Read posts 8 and 18. I believe it's either a short in the fuel pump wiring between the relay and the inertia switch, or possibly a PCM problem in light of post 18.
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What is the PCM? Is that the same as the ECU? It's behind the passenger side kick panel right?
Also, its the # 25 fuse, its a 20 amp Maxi fuse.
nyuk98gt
15 Year Member
RickyII7:
PCM = powertrain control module, or, yes, ECM (computer).
I'm on the road so I can't tell you what the FP fuse number is on my car. (Sorry).
Chris
PCM = powertrain control module, or, yes, ECM (computer).
I'm on the road so I can't tell you what the FP fuse number is on my car. (Sorry).
Chris
Turbo92PGT
Member
I had the EXACT same problem on my mustang. Except mine was intermittant. Then one day I punched it around a corner and the car shut off. I pulled over and tried putting in new fuses and they all blew. Towed the car home. Pulled the CCRM out and replaced that for good measure (junkyard one). No luck. Unplugged the fuel pump etc like you did. Kept blowing.
My problem ended up being the engine wiring harness at the back of the motor. It was hardly noticeable but what happened was the wiring touched against the EGR tube and shorted out a couple wires. Cut and soldered and insulated the wires and it was good as new. I have not had a problem with it at all since.
I have had my motor out of the car and I think I just neglected exactly how I ran the wires.
That would be my guess. Good luck, feel free to email me if you have any more questions.
[email protected]
My problem ended up being the engine wiring harness at the back of the motor. It was hardly noticeable but what happened was the wiring touched against the EGR tube and shorted out a couple wires. Cut and soldered and insulated the wires and it was good as new. I have not had a problem with it at all since.
I have had my motor out of the car and I think I just neglected exactly how I ran the wires.
That would be my guess. Good luck, feel free to email me if you have any more questions.
[email protected]
Problem Solved!
It turns out that the fuse was the computer fuse as previously suggested. The 1998 gt manual is wrong. The MIL eliminators were the culprit. One of the wires was worn and shorting out to the transmission mount. I did some Google searching and found someone with a similar issue. His problem was a shorted MIL eliminator so I though I would check mine out.
Thanks to all who helped!
It turns out that the fuse was the computer fuse as previously suggested. The 1998 gt manual is wrong. The MIL eliminators were the culprit. One of the wires was worn and shorting out to the transmission mount. I did some Google searching and found someone with a similar issue. His problem was a shorted MIL eliminator so I though I would check mine out.
Thanks to all who helped!
nyuk98gt
15 Year Member
Inked12679,
An oldie but goodie thread!
All was good before the installation of the headers and mid-pipe, correct? If so, then something has happened so now we have to sort out what the issue is. I will say that the hotter engine bay may not be a likely cause because lots of people run headers (coated and not coated) and electrical issues do not result.
This is not much as much fun as modding but get the car up on jack stands and carefully check the wiring of the O2 sensors and the wiring harness that runs above the transmission (near the back of the engine). You'll need a mechanics mirror and a decent light. Even then, you will have to feel for melted insulation. If there is missing insulation then there will be a short when the bare wire contacts the body or something else that's grounded. Another possibility is that a wire got a little pulled out of a connector during the recent work, leaving a little exposed metal that can cause a short.
I don't have my Hayne's manual anymore but there are wiring diagrams in the back. Find the harness and see what else is bundled with the fuel pump wires. This will help you to figure out where to start (and where to go) if you don't want to start under the car.
HTH,
Chris
An oldie but goodie thread!
All was good before the installation of the headers and mid-pipe, correct? If so, then something has happened so now we have to sort out what the issue is. I will say that the hotter engine bay may not be a likely cause because lots of people run headers (coated and not coated) and electrical issues do not result.
This is not much as much fun as modding but get the car up on jack stands and carefully check the wiring of the O2 sensors and the wiring harness that runs above the transmission (near the back of the engine). You'll need a mechanics mirror and a decent light. Even then, you will have to feel for melted insulation. If there is missing insulation then there will be a short when the bare wire contacts the body or something else that's grounded. Another possibility is that a wire got a little pulled out of a connector during the recent work, leaving a little exposed metal that can cause a short.
I don't have my Hayne's manual anymore but there are wiring diagrams in the back. Find the harness and see what else is bundled with the fuel pump wires. This will help you to figure out where to start (and where to go) if you don't want to start under the car.
HTH,
Chris
wmburns
SN Certified Technician
+1 on above.
To anyone else reading this thread. There is an ERROR in the owner's manual for some model years between 1996 and 1998. The PCM fuse and fuel pump fuse are labeled backwards. Which means that you may think the fuel pump fuse is blowing when in fact it's the PCM fuse that is blowing.
Another oddity of the 1996-1998 model year Mustangs is the O2 heater circuits draw power through the PCM. Which means a ground fault in any of the O2 heater circuits will blow the PCM fuse. This is a terrible design that Ford changed in the 1999+ model years.
Suggestion. Verify which fuse is blowing. IF the fuel pump fuse is blowing THEN there should be no key on power at the trunk mounted IFS shut off switch. In the same vein the PCM should communicate with an ODB2 reader/scanner.
Be open to the possibility that if after the fuse blows and you are unable to communicate with the PCM, stop and think that maybe it's the PCM fuse that has really blown.
To anyone else reading this thread. There is an ERROR in the owner's manual for some model years between 1996 and 1998. The PCM fuse and fuel pump fuse are labeled backwards. Which means that you may think the fuel pump fuse is blowing when in fact it's the PCM fuse that is blowing.
Another oddity of the 1996-1998 model year Mustangs is the O2 heater circuits draw power through the PCM. Which means a ground fault in any of the O2 heater circuits will blow the PCM fuse. This is a terrible design that Ford changed in the 1999+ model years.
Suggestion. Verify which fuse is blowing. IF the fuel pump fuse is blowing THEN there should be no key on power at the trunk mounted IFS shut off switch. In the same vein the PCM should communicate with an ODB2 reader/scanner.
Be open to the possibility that if after the fuse blows and you are unable to communicate with the PCM, stop and think that maybe it's the PCM fuse that has really blown.
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