I have a 95 f-150 4x4 302 auto, the problem is the fuel pump runs constantly and you have to spray it with starting fluid when the engine is cold to get it to start and when it is running it has a miss when you put it under a load like its losing spark or injector palse. Also has check engine light on but when I hook up the scan tool the pcm won't communicate. I have done many test and pretty sure the pcm has ground and power I have tried couple different pcms still same issue. I am at a loss please repsond if anyone can help. Thanks John

 

A constantly running fuel pump is usually one of two things, a bad PCM or a stuck Fuel Pump relay. Your code issue is probably caused by corroded pins on the Diagnostic Link Connector. In light of the issue happening with multiple PCMs it's time to start checking relays, cleaning connectors, grounds and toss in checking what the battery voltage is with the truck off and running.

What other tests have you run?

 

I have checked voltage at the iac, and reference voltage at tps according to this test the pcm should have good power and ground. I have not changed the pcm relay could that be the problem. Also do you know where all the grounds are located

 

I specifically asked for the voltage at the battery with the truck running and off. It's just to verify your supply voltage is good. The grounds to be concerned with are the bundle near the the battery/start relay and the group on the driver side of the radiator support. It never hurts to check the ground on the engine block. Usually if it is bad you would also have starting issues, same for the battery voltage. I try to verify the simple easy to overlook items first.

There are other grounds for taillights and other systems spread throughout the truck. The ones I mentioned are very common problem areas related to powertrain operation.

 

I have good voltage from battery running and not running I have checked all the grounds I have found with my power probe they seem all to be good

 

Can you define what that means?

 

Well I replaced engine wiring harness turned key on fuel pump primed and shut off it started right up still has small miss when decelerating and is little sluggish but 99% of problem is gone

 

Figured out after adjusting timing it was out a little bit. I guess there was a bad wire some where in the harness causing my problem. Thanks for your help