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1991 ford F-150 fuel problem ( 2 problems)

I have a 1991 ford F-150 XLT big three hundred inline six cyclinder with two tanks that I seem to be having two problems with. The first problem is the fuel drains into the front tank when i am running the back tank. The second problem is the fuel pump does not kick in every time i turn the key , is it suppost to ? I have to turn the key on and off until I hear the fuel pump humming under the truck. Any suggestions or answers would be greatly appreciated. Thank you.

You’ll need to replace the switchover valve/reservoir. There are three fuel pumps: 2 lift (in the tanks) and one high pressure pump. The selected tank and the high pressure pump should run when the key is first turned on and …normal run. This is a common (and dangerous problem…imagine when both tanks are full?

thank you very much for your feed back. I am only aware of two pumps one in each tank. Why is this a dangerous problem? What do you mean by imagine when both tanks are full ? thanks again !

If both tanks are full, then having the rear tank fill the front will cause fuel to spray everywhere(far more fuel is returned to the tank than is consumed by the engine). Ford did switch to having two, high pressure pumps in the tank at some point…I’ve forgotten, but I thought it was in '93. Prior to that, there were two in the tank and one the frame rail under the driver’s foot.

OK cool , thank you very much! you have been very helpful !

There was a technical service bulletin for that problem which indicated that the check valve(s) might be the cause.