Well first want to say hello i'm new to the site...now we are working on brother in laws car and he has a 1990 f150 and it getting spark so know that is not the problem for the car not wanting to start. We have measuered the relay harness and we are only getting 8 volts, is this low or about right. Also the fuel pump is not turning on when switch is turned on with key. I researched some on the site and we found the interia box and reset that. wanted to get any ideas from you guys. Thanks

 

Welcome to the forum! 8 volts is definely not enough, search for some loose/rusty connections. Can you hear the pump when you turn the key on? Have you checked fuel pressure?

 

no the pump does not turn on. we just tested it again and now we are not getting any voltage. Going to do a search but looking for fuses in engine bay can't seem to find them..thanks

 

try to start with replacing a relay, if you have no voltage at it's "output"

 

well after testing seems like from the harness going back to the tank i'm getting 12 volts when checking but only getting 5 volts from harness i guess from computer so i'm guessing it's a bad computer

 

The computer doesn't supply voltage to the fuel pumps, it only turns them on by supplying ground to the relay. There are no fuses under the hood, just fusible links. They are bolted to the solenoid.

 

if you have two tanks then it might be the tank switch

that is what was wrong with my 87