When I fill my truck up (dual tanks) and drive off the rear first, the front tank overpressures and comes out of the filler cap and overflows. Please advise.
I have an 87 F-150 longbed with a 4.9L.Thank you,bobby

 

quick fix: drive the front tank first, then the rear, then back to the front. when you go back to the front there will be about 1/4 to 1/2 a tank the was dumped in there from the rear tank. there was a recall on this, but your truck is too old. why would you drive the rear tank first if you know this happens?

 

This is a relatively straight forward fix... With the '87 you need to change the switching valve on the chassis just behing the high pressure pump.