fuel pump questions
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New User
Joined: Jun 2003
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From: rushville, NY
fuel pump questions
I recently purchased a 1986 F250 4X4 with a 351 auto as a plow truck. the truck was not running, but with a new starter and solenoid it started right up, just as I expected a Ford to do. However, I have to run it off external fuel tanks for now as the on board ones are bad. So here is the question.
When running, the fuel pump does not seem to "fill" the see through filter that is installed near the Carb ( 4 barrel holley) the filter stays about 1/4 full. The return line is truly pumping loads of unused fuel back to the tank. Although the truck runs, it is very hard to start without giving it a shot of either at first, once it is warm it starts right up. It also hesitates under load (running around the back field).
I removed the pump, and although it does seem to pump, if the outlet is plugged, the fuel goes right to the return line. Is this correct? Should there be a certain pressure reached before opening the return line valve? Should the return line have some restrictor valve in it?
Any help would be appreciated
Tom
When running, the fuel pump does not seem to "fill" the see through filter that is installed near the Carb ( 4 barrel holley) the filter stays about 1/4 full. The return line is truly pumping loads of unused fuel back to the tank. Although the truck runs, it is very hard to start without giving it a shot of either at first, once it is warm it starts right up. It also hesitates under load (running around the back field).
I removed the pump, and although it does seem to pump, if the outlet is plugged, the fuel goes right to the return line. Is this correct? Should there be a certain pressure reached before opening the return line valve? Should the return line have some restrictor valve in it?
Any help would be appreciated
Tom
Elder User
Joined: Oct 2004
Posts: 984
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From: Winnipeg, Manitoba
Sounds like you need a fuel pressure regulator, at the least. I do believe(and can be corrected) that these trucks had a low pressure pump in the tank, and a high pressure pump on the rail, to keep things running properly. Carbs only require 5-7 lbs of pressure, any more and you'll have problems, any less...same issue.
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New User
Joined: Jun 2003
Posts: 11
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From: rushville, NY
fuel pump
where would the regulator have been located? I checked both tanks and other then fuel level senders I find no wires that would go to an in tank pump. This is a mechanical pump mounted just below the coil on the drivers side of the engine.
Again, thanks for any advice.+++++++++
Again, thanks for any advice.+++++++++
Elder User
Joined: Oct 2004
Posts: 984
Likes: 0
From: Winnipeg, Manitoba
If it's a mechanical pump, you won't need a regulator for pressure. Where are your alternative fuel tanks located?
The hard start problem may not be related to the fuel pump or tanks either. Has this truck seen an ignition tune-up, as well as a carb tune-up?
The hard start problem may not be related to the fuel pump or tanks either. Has this truck seen an ignition tune-up, as well as a carb tune-up?
Elder User
Joined: Oct 2004
Posts: 541
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From: Fleming Ga
If it is hard to crank when cold and requires ether but cranks fine when warm, then you maybe have a leaking power valve in your carb that is leaking all the fuel from the bowls after setting awhile. Before trying to start next time when its cold, look in the top of the carb and open the throttle a few times. It the accelerator pump doesn't pump fuel into the carb then the carb is probably dry. Using ether allows the motor to run on the ether long enough for the fuel pump to refil the carb bowls.
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