Fuel issues
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Joined: Dec 2011
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Fuel issues
I have a 78 f150 4x4 with a 351m.. Starts fine cold, I have plenty of fuel in clear fuel filter, once motor is up to running temp, the fuel filter goes dry and truck doesn't run.. Have new tank, sending unit fuel lines, mechanical pump... Not too sure what's going on.. Any help would be appreciated!
Post Fiend
Joined: Dec 2006
Posts: 9,111
Likes: 3
From: Lexington Mo
Sounds like you may have a good ol' "Vapor Lock" issue on your hands. That fuel line may be close enough to the engine block, or head and getting warm enough to turn the gasoline from a liquid, to a vapor.
There are several fix's for this. Cooing canister, some guy's have even put wooden clothes pins on the metal gas line, letting the wooden pin absorb the heat from the metal. You could even try rubber fuel line, from the gas pump, right to the fuel filter and then to the carb. And route that rubber away from the side of the block, and away from the heads. If that keeps you going, then you know the problem.
Unk Bob
There are several fix's for this. Cooing canister, some guy's have even put wooden clothes pins on the metal gas line, letting the wooden pin absorb the heat from the metal. You could even try rubber fuel line, from the gas pump, right to the fuel filter and then to the carb. And route that rubber away from the side of the block, and away from the heads. If that keeps you going, then you know the problem.
Unk Bob
Elder User
Joined: Jan 2014
Posts: 898
Likes: 3
From: Chillicothe, IA
Just some questions to help get this answered.
Is this happening during idle, or driving, or both?
Did you replace rubber lines metal lines or both?
Did you put in an exact match to old tank? Vented or not?
Tank full?
Was it 107 degrees out?
Was carb rebuilt also?
Is this happening during idle, or driving, or both?
Did you replace rubber lines metal lines or both?
Did you put in an exact match to old tank? Vented or not?
Tank full?
Was it 107 degrees out?
Was carb rebuilt also?
Fleet Mechanic
Joined: Sep 2014
Posts: 1,626
Likes: 78
From: NE Texas
Further to what DB4 said- When you put on the new tank was it a vented or unvented tank? On 2WD the vent comes out dead center of the top of the tank. If you have an unvented tank with a non-vented cap, after a while the pressure drop in the tank will equalize with the fuel pump pressure and - bummer- no gas comes out. When it stops running, remove the gas cap - if you get a whoosh inrush of air into the tank, you have found your culprit. Like DB4 said, you could have a blocked vent on your gas cap, a plugged vent line, or even have a non-vented cap. Luckily a vented cap is a cheap fix.
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