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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / November 200485 Ford 460 starts & dies... help with ideas
I have a 1985 Ford F250 with a 460 gas hog engine. It has a holley double pumper carb which was put on by the previous owner. It ran fine one day, no problems. The next day when I started it it starts fine, runs approx 30 seconds, and dies. It does this repeatedly, but will not run longer than approximately 30-45 seconds without dieing. It acts like it runs out of fuel, but I am doubting that... Here are some of the things I have tried. It has dual fuel tanks with an in tank pump/filter in each tank, but the engine does the same regardless of which tank it is drawing from, so I dont think it is a plugged pump filter. There is no supplemental pump, or in line filters on the rail. It does have the small special filter/check valve/return port on the front of the engine between the steel fuel line and the rubber line to the carborator. I replaced that with a new one from ford ($46!), but the problem persists. I have had a mechanic I occaisonaly look at it, and he too is stumped. He tried a different electonic ignition module, a different coil, and new fuel pump relays, but the problem persists.... The carb has internal filters on the two input fuel lines. They appear clean, and I tried it with them removed, with no change to the problem. After the engine dies, if you move the throttle connector, you can hear/see fuel spraying into the carborator. Also, if you remove the fuel hose right at the carborator right after it has died, there is still pressure in the line. I removed the vacuum line that goes to the distributor, thinking maybe that was messed up, but the problem was the same. If you take the fuel hose off and crank the engine, it appears to be putting out a significant volume of fuel. I hooked one of the spark plug wires to an extra plug, and it appears to have spark as it quits, just slows down as the rpms die off. In summary, I'm stumped. I really don't think its a fuel availability problem but perhaps something in the carb, but I dont know what. My mechanic is stumped, and I need the pickup for work. Any input you can give would be greatly appreciated. Did did you substitiue the pickup in the distributer?Did you hookup a temporary vacuum gauge to one of the vacuum ports? > I have a 1985 Ford F250 with a 460 gas hog engine. It has a holley > double pumper carb which was put on by the previous owner. It ran [quoted text clipped - 40 lines] > mechanic is stumped, and I need the pickup for work. Any input you > can give would be greatly appreciated. I'm convinced it is a fuel supply problem. I hooked the truck up to an external, gravity feed fuel tank, and the truck runs fine. While doing this, I ran the regular fuel lines to a tank where I could watch them. While the truck is cranking, the fuel pump puts out fuel, but after it starts and the key returns to the run position, there is no - none - fuel coming out of the hose from the pump. The truck has two fuel tanks with in tank pumps, so I do not believe it is a pump issue, unless they both failed at the same time. I was told that in 86 they began putting a oil pressure shut off switch on the trucks, but I looked and I don't have one (mine is an 85). I tried bypassing the safety shut off switch, with no positive results.... Any other ideas would be greatly appreciated.... > Did did you substitiue the pickup in the distributer?Did you hookup a > temporary vacuum gauge to one of the vacuum ports? [quoted text clipped - 42 lines] > > mechanic is stumped, and I need the pickup for work. Any input you > > can give would be greatly appreciated. > The truck has two fuel tanks with in tank pumps, so I do not believe it > is a pump issue, unless they both failed at the same time. I was told > that in 86 they began putting a oil pressure shut off switch on the > trucks, but I looked and I don't have one (mine is an 85). I tried > bypassing the safety shut off switch, with no positive results.... Any > other ideas would be greatly appreciated.... Take a close look at your tank changeover switch. If it has failed, it may be denying power to both fuel pumps. > I'm convinced it is a fuel supply problem. I hooked the truck up to > an external, gravity feed fuel tank, and the truck runs fine. While [quoted text clipped - 4 lines] > >>snip<< Find the "hot" wire going to the pumps. (Your descrip. above tells us it's getting fire ONLY when the ign. switch is in the "start" position--it must also have fire when the ign. sw. is released & in the 'run' position.) Find a wire that is 'hot' only when ign. is in run position. Fuse a wire-link from this ign. wire to the fuel pump wire(Splice it in.). If it runs ok then, you could probably run this way indefinitely. Best to find a defective relay, tho', as another poster recommended. HTH & good luck. s > I have a 1985 Ford F250 with a 460 gas hog engine. It has a holley > double pumper carb which was put on by the previous owner. It ran [quoted text clipped - 40 lines] > mechanic is stumped, and I need the pickup for work. Any input you > can give would be greatly appreciated. The fuel pump relay should be on the firewall, engine compartment, driver's side. I would pull the relay and jump it with an ammeter to monitor current draw. I believe the circuit is from battery to relay to tank selector switch to each fuel pump.. as both tanks are involved, I'd suspect upstream of the selector switch. You could also use a test light to backprobe the output of the relay to verify you're not losing the relay.. Regards, Jim |
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