Have a 1989 Ford F-150 with the 300ci six with fuel injection, the problem is you never know when it will start, when the key is turn on and you hear the high pressue pump charge up it will start, but when the key is turn on and you do not hear the high pressue pump charge up it will not start, and you have to keep trying. I have replaced the high pressure pump with a factory pump, I have replace a fuse link in the system, and the fuel control relay. Looking at the wiring diagram the only think left is the EEC relay and the ignition switch. Any help would be appreciated. Thanks bskull

. Test all underhood and underdash fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-t...tml#post252145

Test for "power through the fuses."

. Remove fuel pump fuse and fuel pump relay, clean contacts with steel wool or abrasive cloth, and apply a light coating of dielectric grease. It would be a good idea to remove each underhood fuse and relay, one at a time, and clean them. This has been a recurring problem on older F-150s. It would surprise me if the problem went beyond this.

. Check connections to the fuel pump for corossion--clean and apply light coating of dielectric grease. Be sure to disconnect the negative battery cable first and keep a fire extinguisher handy.

. Test/replace the Electronic Engine Control (EEC) relay, if the problem persists. Beyond this, the problem may be with the PCM or harness.