I have a 1988 ford F150 wtih dual tanks. I can't seem to get the rear tank to work. I have voltage going to the rear fuel pump, when the selector switch is on rear tank but, it empties the front tank all the time. The rear tank is always full even when I have the switch on the rear. Can anyone help?

 

What happens when you put the switch on the front tank? I've seen this problem before, but normally the tank that the switched has selected fills the other tank, not the other way around as you described.

 

I think I know what is going on. The late 80's trucks use a mechanical selector valce the relies on the low pressure pump in the tank to switch over. This switch needs to see a minumum of 3lbs of pressure to switch over. If the pump in the tank is bad or not coming on for any reason, even if you switch to that tank, the valve will not switch over. The other problem is if this is whats happening, you put a big strain on the frame mounted high pressure pump because it does not have the help of the low pressure pump when you switch to the other tank.

Hope this helps.

--Mike

 

Thanks for your help! I think I understand what you are saying. The high pressure pump is still pulling fuel out of the front tank because the valve is not getting pressure from the rear tank pump. I thought that this might be the problem but I wasn't sure. It seems to make sense because my rear tank never empties out no matter which tank I would switch to. Thanks again for your reply