Son has 87 f150 w 4.9, efi, ecc-iv, duel tanks. only the rear tank has worked since he had it. Truck would turn over and not run. Try it again later it would run. Notice sometimes fuel pump ran and some times not. This is the three pump system. I can "hot wire" the fuel pump by running direct from battery to pump - pump runs truck wont. I can hotwire it by jumping the yellow and red/yellow at the fuel pump relay. Again pump runs but truck wont. Is that because both methods bypass the relay? If its a bad ground where any I looking for it? The ecc is grounded to inner fender. We tried a junk yard fuel relay and a junk yard ecc - no dice. I know thats not a great way to fix it but times are tough.

any help is greatly appreciated. thanks in advanced

 

You might check the TFI ignition module. It controls spark and fuel pump operation.

 

we did that. now we get code 87 - faulty fuel pump relay circuit. tyring to find the faulty part

 

Check the chassis grounds. Engine to chassis, frame to bed and ohm out the FP ground at the tank to make sure there is no resistance to the frame.