Air in fuel.....help!!!!!!!!!!!!!!!!!!!

[Bray14]

1991 7.3 f350 please help going crazy. starts up but revs up and down on its own. Dies when you drive. Filter new, return lines and caps new, fuel line from tank new, added in line electric fuel pump. Tested line with clear going into filter and have major air bubbles. This is driving me crazy. Any help would be greatly appreciated.

 

[79jasper]

Well first make sure you have fuel in the tank.
Then make sure you have way over a quarter tank. Just fill er up.


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[Bray14]

Thanks but has full tank. Dropped the tank and made sure it was clean and in working condition. pick up and sock looked just fine. Thought maybe it was the pick up pump which is why we added electric pump on frame rail. So want this truck back running. It is my daughter love. any other ideas

 

[79jasper]

Did you leave the factory pump hooked up?
Only a few things it could be.


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[Bray14]

Tried it both way with factory pick up pump and by passing it. Still same problem. I know it can only be a few things which is why this is so frustrating.

 

[Bray14]

Ran 3/8 rubber hose for new fuel line from tank to front.

 

[79jasper]

Wait, single tank or dual?


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[Bray14]

dual tank but only use the back tank. Front tank has a rust hole. Switch works fine as far as we know.

 

[Bray14]

nothing changed when electric fuel pump was added. Still ran bad.

 

[79jasper]

Need to bypass the selector valve. They can suck air.
Also check all the fuel line fittings.


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[Bray14]

will give it a try. so few things that can go wrong with these but holy crap this is a pain.

 

[Bray14]

Going to take electric pump and run it out of a fuel can and see if it still does the same thing. That should answer if air is coming from either tank. We love our 1991 f350 dubbed "Betty White" so any help would be great appreciated.

 

[79jasper]

Where did you place the electric pump?



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[Bray14]

on frame rail in the middle of cab. At the pump its is over 5lbs psi at the fuel filter it is only 3.25lbs.

 

[79jasper]

That means the air is coming in before the electric pump.
But I would venture a guess as the 3.25 is inline with the mechanical pump.


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