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Fuel lines to the fuel pump

I just replaced my rear fuel tank, brand new tank and pump. I know the fuel lines were a pain to get off even using the correct tool( trucks almost 30 years old). When I put in the new tank I was unable to get the fuel lines to snap on. So after an hour or more of trying and trying (even tried soaking with penetrating oil). So I guessed maybe they don't click on, and just used the clips. Now the truck won't get gas from the rear tank, but I can hear the pump running (front tank works fine). Do they have to click in to build pressure, or could it be something else.
 

Fellro

Moderator
Staff member
Tghe pumps will run and self prime without fuel lines on them. If they were loose you would have a major fuel leak. Sounds like the switching mechanism isn't working. That can be either a mechanical passive switching device, or a simple check valve depending on year.
 
Can it be the switching mechanism even though the truck runs when I have the switch on the front tank. Once I switch it to the rear tank it reads what's in the rear tank at a 1/4 tank and just dies. When the switch is on the front tank it reads a full tank and stays running perfectly fine.
 

Fellro

Moderator
Staff member
Yes, the mechanism is not electrically connected, so it acts independent of the pumps. If it sticks such that only the front tank can flow, it would do exactly as you describe. I have a similar issue, and as a result I do not run the rear tank. Mine also got to leaking... Some times they fail such that it returns the excess fuel back to the wrong tank, allowing it to overflow.
 

Fellro

Moderator
Staff member
You haven't answered what year your truck is, so it can be different. 87-91 had a canister looking device on the frame rail ahead of the front tank, 92-97 have a check valve in the fuel lines themselves.
 
So when you turn the key to the on position without starting, the sound you hear from the fuel pump getting primed is the sound I hear. I start the truck using the front tank, after it's idling I switch to the rear tank and it's a constant sound of the fuel pump priming and the truck dies cause there's no gas goin to it. I could switch it to the front right before it dies and runs fine.
 

Fellro

Moderator
Staff member
Just fixed it, kinked fuel line. I guess the hassel of feeding the filler tube over the frame and back to the neck I forgot to watch the fuel lines. I dropped the tank and pulled the lines and was sprayed with gas, so I new gas was goin thru. So I started to follow the lines found nothing abnormal looked at the connections and notice the supply tube looked like I was bent at one point. So I straightened it out put the tank back up filled it with gas and it started fine idled fine. Now I gotta keep my fingers crossed cause I'm going to test drive it and make sure it could keep up the demand of wide open throttle.
 

Fellro

Moderator
Staff member
Well, that for certain can cause troubles... gotta love the simple fixes.
 

fatherdoug

Tonto Papadapolous
So you have the have the canister style. The problem now is they are hard to come by.

Plain and simple, the valve is stuck to the front tank. The rear pump simply can't get fuel past the valve.
I did manage to actually find a listing for a new one...
https://www.tascaparts.com/oe-ford/...4p5JjWNlTgfKKBKt2Hqinr7zuo_g1Q0XOMRoCcD3w_wcB

After a month long search for one of the mechanical switching valves, I finally found one in Massachusetts collecting dust on a dealer's shelf.
 

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