460 Fuel Starvation?
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460 Fuel Starvation?
1987 F-250 with a 460 (carburated). When under any sustained load (such as a grade) the truck loses almost all power and will not rev. Also occasionally backfires through the intake/air cleaner. If you attempt to floor it it will eventually die completely. But for short grades or flat land with no load, it seems to run normally and has plenty of power.
Fuel filter in carburator is clean and the fuel regulator appears to be clean as well. Truck has no catalytic converter. happens on either tank, so I don't believe it's a pump issue. Any ideas?
Fuel filter in carburator is clean and the fuel regulator appears to be clean as well. Truck has no catalytic converter. happens on either tank, so I don't believe it's a pump issue. Any ideas?
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About 85k. Really runs great other than this problem. Good compression, oil pressure and never even gets to the halfway mark on the temp gauge.
One other issue that probably is not related: Occasionally will NOT come off high idle when warm...
One other issue that probably is not related: Occasionally will NOT come off high idle when warm...
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To add to the difficulty of the problem, I found today that 1987 does NOT have a test of the computer. EEC IV began in 1988, so I can't even scan for codes from this version computer.
If anyone has any ideas, please help? I need this truck for work.
If anyone has any ideas, please help? I need this truck for work.
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Is your fuel pump in the tank, or the frame rail? If it is in the tank, it could be the old "sock" problem. The strainer on the fuel pump gets clogged.
Good Luck.
Frank
Good Luck.
Frank
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The truck has just two low pressure pumps inside the tanks. No high pressure pump on the frame as it is carburated. I have not pulled the tanks apart yet because the problem happens on either tank. Have there been instances of BOTH pumps having problems at the same time?
The only thing else in the fuel line is the selector switch for the tanks, but I don't see any means of filtration there...
The only thing else in the fuel line is the selector switch for the tanks, but I don't see any means of filtration there...
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From: Cloud USA
Maybe the fuel pressure regulator? The 460 you have has the hot fuel option which circulates the gasoline back to the tank and holds a certain pressure, like an EFI. THis prevents vapor lock. Something to look into.
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From: Gilbert, Arizona
I have the same problem, butcher. My fuel lines and filter are in good shape, but I haven't dropped the tanks to check the fuel pump socks yet.
Have you disconnected your fuel line from the carb and checked the fuel flow? My pumps seem to be really weak, I'm surprised it runs as good as it does.
Scott
Have you disconnected your fuel line from the carb and checked the fuel flow? My pumps seem to be really weak, I'm surprised it runs as good as it does.
Scott
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From your description, with the occasional backfire from the intake, it sure sounds like fuel starvation. You may end up taking things apart piece by piece and cleaning/inspecting as you go.
I had a car once that would plug up its sock in the tank after being run for 15 minutes on the road. Drove me crazy trying to find out what was wrong. Thought it was heat related due to the time element. But it was thin rusty bits floating around in the tank. 15 minutes of a running big block on the road, sucked up enough junk to restrict the sock pretty good. Then when parked long enough, the junk would fall off without the suction to hold it on. So it would run fine again, for a while. That was one of the most puzzling troubleshooting jobs I ever had to do.
I had a car once that would plug up its sock in the tank after being run for 15 minutes on the road. Drove me crazy trying to find out what was wrong. Thought it was heat related due to the time element. But it was thin rusty bits floating around in the tank. 15 minutes of a running big block on the road, sucked up enough junk to restrict the sock pretty good. Then when parked long enough, the junk would fall off without the suction to hold it on. So it would run fine again, for a while. That was one of the most puzzling troubleshooting jobs I ever had to do.
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c_rossman nailed it
Turned out to be the vapor seperator/fuel regulator. Finally went to a dealer and was in the middle of describing the problem when he knew what it was. Turns out Ford replaced many thousands of these with a different model. Something to do with the orifice size for the return line to the tank. Kind of weird that new trucks in 1987 didn't exhibit this right off the lot though. The replacement seems just as restrictive when you blow through it as the old one. But I'm thrilled to have my work truck back and able to go up hills again.
Thanks for the help!
Thanks for the help!
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