need help with fuel problem
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need help with fuel problem
can someone help? my 83 f-250 4x4 has a carb 460 and i am having trouble keeping gas to the carb. i recently changed both in tank fuel pumps. it ran great for about 3 months, but all at once it started starving for fuel.i can't imagine both fuel pumps would go out at the same time. i changed inline filters and i get gas at the carb, but it doesn't seem to have the pressure it should have. the truck will start, but then die after about 1-2 min. does the selector switch have anything to do with the pumps? also is there a oil pressure switch that i may be overlooking? i have yet to check the relay but i would think there would be no fuel if it were bad.
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From: Virginia
also is there a oil pressure switch that i may be overlooking?
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where is the oil pressure switch located? and how do i check it to see if it is working properly? I still think the selector switch may have something to do with my problem. It has to send a signal to the pump in order for it to operate and if the selector is bad, won't this prevent the pumps from working? The only place I have been able to locate a new selector switch from was the ford dealership and I hate to spend that kind of money unless it is a last resort.
Last edited by 83farmtruck; Dec 14, 2003 at 09:48 PM.
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From: Virginia
Well, the selector switch could be bad, but why does it run a little bit and then quit?
And I am sorry, but I don't know the exact location of the pressure switch on your engine.
And I am sorry, but I don't know the exact location of the pressure switch on your engine.
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I recently had a problem similar to this and it turned it to be the relay itself. Since power is supplied to the fuel pump directly from the soleniod, the truck starts, then the relay switches circuits. This circuit has the oil pressure switch and an inertia switch. My truck would start (power supplied by the solenoid) and then die once it turned over. Changing the faulty fuel pump relay solved it. The relay is located inside a black box underneath the driver's side hood hinge.
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Well, I am still at a loss with what is wrong with my truck. I have replaced the fuel relay, tried going around the selector valve, and nothing I have done has been able to keep my truck running more than 1-to 2 minutes. I am getting fuel at the selector valve when I break the line and turn it over. I am also getting fuel at the carb when I break the line there and crank the truck over. I have even gone as far as taking the fuel pumps out of the tank and running them in a can of gas and they seem to have good pressure and did not kick out. But when I hook everything back up and start the truck, it will run great for only a minute or so and the just quit pumping gas to the carb. I can break the line on the carb right after it dies and it is dry. But when I crank it over I get gas again. I even had someone tell me to try a new ignition, so I thought what the heck for $8 bucks it was worth a try but of course that did not help. Can someone please tell me what I am overlooking? I would love to get this thing out of the garage.
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From: Callahan US
There is a fuel regulator right in front of the carb. Fuel line going in and one going out and a return line. This little device has a screen in it where the fuel line enters it. Since the fuel filter in a 460 is in the carb, any trash that is in the gas ends up caught in this screen. I removed mine and blew compressed air across the inlet opening. This created a vacuum and pulled the trash out. I didn't atempt to blow straight into the regulator not knowing what is in it. This caused me trouble for months till I found the screen.
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From: Virginia
It sure sounds like your secondary fuel circuit to the fuel pumps is bad. Like the other poster said, the fuel pumps are run directly when cranking, but they switch over to the pressure switch and the relay for running. Sounds like you are filling the carb on start-up, and then the fuel pumps have no power after it starts, and the carb takes a minute and then runs dry.
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Where do I start to check the secondary fuel circuit to see where I am losing power? After changing the fuel relay I don't have a clue about the next step in trouble-shooting the electrical circuit for the fuel system. I know it is going to be something small that I am just over looking but I swear this truck is going to drive me nuts first.
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From: Callahan US
If it is like my truck there is not a secondary fuel circuit. The oil pressore switch and the fuel regulator are the only things that regulate the fuel. The pumps run continuously as long as there is oil presssure. The fuel regulator is what moderates the fuel pressure so there is no need for a secondary fuel circuit. I have just went through what 83FARMTRUCK has gone through. Look at the screen inside the regulator and if I am wrong then so be. If you think you have a power problem to the pumps then why dont you check power (AT THE PUMP) when the truck dies. If power shuts off before engine dies then you have relay or switch problem. If you lose power to the pumps after engine shuts off you have fuel delivery problem like filter or (screen). The power would have been shut off by the oil pressure switch then.(which is normal.)
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From: Virginia
"If it is like my truck there is not a secondary fuel circuit"
Sorry, I should have said secondary fuel electrical circuit.
The Haynes manual in the auto store has the electrical diagram of the fuel electrical circuit/pressure switch/relay/pumps, in it. It's called "hot fuel handling" in the diagram.
Sorry, I should have said secondary fuel electrical circuit.
The Haynes manual in the auto store has the electrical diagram of the fuel electrical circuit/pressure switch/relay/pumps, in it. It's called "hot fuel handling" in the diagram.
Last edited by Franklin2; Dec 29, 2003 at 06:05 PM.