I just purchased a 90 f150 but there is a problem somewhere in the fuel delivery system. I assume its a fuel pump problem but I want to check all stops before I replace it. My question lies with the selector switch. With the switch set on the front tank, and in the KOEO position, my test light shows power on the red wire that leads to the front pump but not on the dark brown/yellow that leads to/form the same pump nor on the yellow/white that leads to the gauge. Would this indicate a switch problem or pump problem? I have the same results with the switch set on the rear tank with the exception that neither wire leading to or form the rear pump shows any power. It was assumed that the rear pump never worked to begin with, or so I was told. I only have access to a test light so I can't tell the voltage or the such and I'm not very electronically inclined to understand what I should be checking for and how with a voltage meter anyway.

I have no yet tried grounding pin#6 on the pump relay yet. As for that I have another question. With grounding that pin, doesn't that really just bypass the pcm relay in turn checking if that relay works or not?

Please help if I am checking the selector switch wrong?
Also, I am using a schematic I stumbled across - http://i54.photobucket.com/albums/g9...el1990F150.gif