fuel gauge problems

Oct 05, 2004 1 Replies

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David Coleman 21 years ago

I have a 1988 f-150 with the 4.9 EFI engine, maual transmission. When I first bought the truck, the rear gas tank would work fine until it got down to about 3/4 of a tank. Then it would start bouncing from full to empty and about the time it got to 1/2 full, it fell to empty. The front tank worked fine. Now the front tank does the same thing. And I have noticed that if I fill both tanks,. the back tank pumps into the front tank until it is about 1/2 full. Which means the front tank runs over.

Any ideas or experience with a problem like this??

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Big Al 21 years ago

I had a problem like this with a Ford truck one time. There is a valve under the truck that switches the fuel line, vapor line and return line from the engine. On mine there was a recall for the valve. Sorry I can't remember what year the truck was, but it was the first port injected 300 six. This valve is a large plastic thing that looks like it has a small power brake booster on one end, has about nine lines going to it. The valve is powered by the fuel pumps. If the front pump is on it switches everything to work with the front tank. Moving the switch from front tank to rear switched the power to the rear tank. And that pump moves the valve to work with the rear tank. On mine, when the rear tank was selected, the return from the fuel injector would dump into the front tank and it would overflow.

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