Hot Fuel Problems
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New User
Joined: Dec 2004
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Hot Fuel Problems
I have an '85 F250 460 with twin tanks and the "hot fuel" system. Last winter the front pump quit working and I have been running the rear tank only since then. Last week the rear pump quit and now I am trying to troubleshoot the tanks, pumps, and relays. I have a couple of questions:
Any help or suggestions would be appreciated.
- Where is the oil pressure switch which controls the pump circuit?
- Where is the relay that switches power from pump to pump?
- Are there any problems that occur more frequently on these systems?
Any help or suggestions would be appreciated.
Elder User
Joined: May 2004
Posts: 506
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From: Edwards Air Force Base
Welcome to my nightmare. Unfortunately it was a while ago so I gorgot which two pins but you don't have a lot of choices so....
The pump won't run unless you take your diagnostic plug and jumper two pins. To clarify, it will run for a few seconds when you first turn on the ignition but then will quit unless you jumper those pins.
Second, just because the pump runs when you put 12VDC on it doesn't mean it is good. I have changed 10-15 pumps that ran on the bench but wouldn't pump gas out of the tank.
You MIGHT have a good pump if your little 1 1/2" piece of rubber hose is shot though that goes from the actual in tank pump to the pickup tube. I have seen this often where the hose has a hole in it so the pump just picks up fuel and then dumps it back in the tank instead of the fuel line.
If you have the pump out already, and the rubber hose is not shot, then get a pump and replace it. You have it out already anyway. Then if you stick it in and it works, you know your other pump is shot also since the relays, oil switch etc must be good if that tank is working. If it doesn't work, you still needed a pump for the other tank since it died while this one was still working before.
Basically, you KNOW you need at least one pump if not two. These pumps do go bad often. I mean really it has been almost 30 years. -ggg- I had to change both of my in tank pumps already and have done many on other people's cars that are about this old as well. I just did a Jeep Cherikee a couple weeks ago so it isn't a Ford thing, it is just an age thing.
Lee
The pump won't run unless you take your diagnostic plug and jumper two pins. To clarify, it will run for a few seconds when you first turn on the ignition but then will quit unless you jumper those pins.
Second, just because the pump runs when you put 12VDC on it doesn't mean it is good. I have changed 10-15 pumps that ran on the bench but wouldn't pump gas out of the tank.
You MIGHT have a good pump if your little 1 1/2" piece of rubber hose is shot though that goes from the actual in tank pump to the pickup tube. I have seen this often where the hose has a hole in it so the pump just picks up fuel and then dumps it back in the tank instead of the fuel line.
If you have the pump out already, and the rubber hose is not shot, then get a pump and replace it. You have it out already anyway. Then if you stick it in and it works, you know your other pump is shot also since the relays, oil switch etc must be good if that tank is working. If it doesn't work, you still needed a pump for the other tank since it died while this one was still working before.
Basically, you KNOW you need at least one pump if not two. These pumps do go bad often. I mean really it has been almost 30 years. -ggg- I had to change both of my in tank pumps already and have done many on other people's cars that are about this old as well. I just did a Jeep Cherikee a couple weeks ago so it isn't a Ford thing, it is just an age thing.
Lee
