2008 f150 STX with a 4.6 liter engine. I’d turn the key and nothing happened except the sound of the starter relay clicking once. Battery good. Starter fuse good. Starter and PCM relay good. Had voltage to the bottom slot where the relay plugged in. Had voltage to the right slot where the relay plugged in when I turned the key to start. When I jumped the top & bottom slot with a piece of wire the starter would turn and the truck would start. As for the left slot the relay plugs into, I’m not sure how to establish wether or not the PCM is providing ground for it, but it seemed that was the issue. I replaced the neutral safety switch and the problem resolved with no further issues for a week. When I got in the truck to go to work a week later, same problem. Turned the key. No crank, no start. Could hear the starter relay click each time I turned the key. Battery still good. All relays and fuses still good. I jumped the starter relay to get to work. It wouldn’t start when I got there, but two hours later it started without issue. I ran a short errand and it started twice more with no issue. The next morning when I left work, same issue. No start, no crank. Battery still good. Everything else unchanged. I jumped the relay to get home. Stopped somewhere on the way home and had to jump it once more.It started without issue after I got home. Four hours later I got in the truck to go to town. Same issue. I jumped the relay. Once I got to town I turned it off &:started it back with no issue. Got home & started it twice more over two hours’ time with no issue. I have a sneaking suspicion it won’t start without jumping the relay tomorrow morning. Thoughts anyone? I’ve had my truck since it was new, and I really like it, but I’m ready to set fire to it at this point. Frustrating as all get out.

 

I’ve read every forum thread and watched every YouTube video on the net, and still I haven’t a clue what the problem is.

 

I am dealing with this exact same issue. I changed the starter relay and the same issue. My battery and alternator are new and I am starting to think its the battery.

 

Mine seems to have resolved on its own for now. It hasn’t failed to crank in since the day I posted the thread. No idea unless the anti theft module is going bad. Has a new neutral safety switch, new starter relay, and new ignition relay. I’m sure it’s waiting until I have somewhere really important to be.