Confirmation of FDM crossover problem? 1991 F150 5.8
 

So one item on my to do list is to drop both fuel tanks, clean them up and repaint. Since I suspected the front tank of having a leak, it came first. I got around to dropping it last night.

I couldn't find anything that would fit tight/exactly into the fuel lines, and since I figured the plug was more to keep dirt out, I used a bolt that fit closely and taped it in place [as I didn't have any hose clamps available.

Went to start the truck after everything was buttoned up and it would turn over, almost fire, but not start. Then I noticed the ever present smell of gas. Got out, looked underneath, and found what must've been a half gallon of gas on the shop floor. :-X15

So this time I turned on the key, but not to start, and looked and sure enough, fuel was practically pouring out of one of the lines. I didn't have a choice but to kink the line and tape the crap out of it as I didn't have any other materials to properly plug the line.

So I'm just wondering, with fuel dumping out of one line to the front tank when the rear is selected, is this confirmation of the FDM crossover problem, or would it have to be dumping out of both lines?

Has nothing to do with the crossover problem, that fuel crossover problem is a bad valve inside the tank.
What you have is normal.

Okay... so, for the sake of learning a thing or two, why is fuel coming out of the front tank line when the rear pump is activated?

The front tank check valve is not there, it's in the tank you removed... Remember?

Hehe... yes, I remember. ;) I guess I didn't realize the check valve was inside the tank itself- I guess I've just been confusing myself. :D

I just couldn't help myself.. You left yourself wide open and this old smart a$$ jumped all over it!!!!!:-X24