1990 fuel tank issue

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Sep 28, 2007 | 12:06 PM

firemanshemi

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1990 fuel tank issue

I just bought a 1990 F150LB 6cyl. for my 16 y/o Son. The previous owner said that the rear tank fuel pump did not work, no problem we only needed the front. So, the rocket scientist son of mine went to fuel up, and yes he filled the rear tank and not the front. So he ran out of gas. Now the rear tank pump runs at a high pitch all the time when the selector is in the front position, and not at all when in the rear position. It also pushes fuel out of the rear fuel fill. I started siphoning the rear tank, and that stopped the flow of fuel. What I want to do is just cut out the switch altogether, and cut all power to the rear tank for good. How do I do that? please let me know if you can. Thanks, father of a rocket scientist

Sep 28, 2007 | 12:35 PM

kcb37

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If you want to do that all you have to do is find the plugs for the pump and unplug it. If it is running when the front tank is on and not the back you may have a bad switch though.

Sep 28, 2007 | 01:44 PM

fordmancounty

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if my memory doesn't fail i think there was a recall on the over flow problem with the tank's.

Sep 29, 2007 | 01:31 AM

fmr9

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If you have fuel coming out of the rear fill neck, the check valve in the rear pump is bad. Both pumps have a check valve to keep fuel from going into the tank not being used. The only way I know to stop the flow of gas to the wrong tank is to drop the tank, and plug the lines . If you are going to that much trouble, might as well replace the pump and have both tanks to use. With only the front tank, your son is going to be driving about 200 miles and need to find a station.
Good luck Frank

Sep 29, 2007 | 03:10 AM

StealthWyvern

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Quote:

Originally Posted by fmr9

Is thier a way to tell which pump needs to be repalced? When I use my rear pump about 1/4 of that tank ends up in the front tank(originally empty) before the rear one is empty..... Now I can't notice anything with the front tank tell I run about 3 tanks in the front back to back. Then i'll have maybe 1/8 of a tank in the rear.

Sep 29, 2007 | 08:41 AM

fmr9

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A checkvalve is just a spring loaded ball in the flow of fuel. The spring pushes the ball onto a seat and seals the flow off. Any flow coming from the direction of the spring, pushes the ball down harder. Flow coming from the other direction pushes against the ball until it compresses the spring a little and lifts off the seat. Each tank has a fuel pump, and each pump has a checkvalve. The checkvalve is there to let the flow move away from the pump, but not let the flow move towards the pump. If the spring is weak or broken, the seat damaged or worn, or if the ball is stuck in the open position, the fuel flows the wrong way thru the pump not being used and fills the tank not being used.
I think you just asked what time it is and I told you how to build a watch, but it is much easier to figure out the problem if you understand how it is supposed to work.
Sounds like you may have problems with both tanks.
Good luck Frank