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
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you didn't mention if you were getting spark when the engine won't start. have you checked for spark? If no spark could be a pip sensor or ignition control module problem.

 

we have spark at coil and spark plug

 

You stated before you hot wired the pumps to turn on, you have spark, now you need to check the fuel pressure.

 

we have replaced fuel pump relay, tfi, coil. The only way i can get it to run is by jumping the yellow wire (constant power) to the red wire (on power). this is at the fuel pump relay. you can't hear the pump run when you turn the key to on but it runs when you start it. Dont know why it works and would love to figure out the problem but for now it runs.