My 99 F150 was doing fine then left mt stuck when it would not turn over. I have replaced battery, starter, solenoid & cables. When I turn the key I get a click but doesn't crank. I can jump across the solenoid it fires right up but the key won't start it. I have been able to keep turning the key back and forth getting it to crank intermittently. What am I missing?

 

I recommend checking the relays or the ignition switch.

This is NOT the ignition switch


THIS IS AN IGNITION SWITCH:

 

Your truck will only start in P or N. Before you take lots of stuff apart, try moving the gear selector to N, then a little bit on both sides. If you can get it to start by doing this, then the cable from the gear selector to the transmission has slipped a cog and the Neutral Safety Switch is not working right. The NSS lives on the transmission as I recall.

As was already posted, the Ignition Switch is high on the list of usual suspects. Turning the key and getting momentary joy tends to point to the ignition switch or the linkage between it and the ignition lockset.

 

If you're jumping the starter relay on the firewall and it starts, I would replace the relay.

 

The neutral safety switch is called a MLPS. It could be out of adjustment. It also tells the PCM which gear you have selected.

Correct me if I'm wrong, but doesn't jumping the firewall relay bypass the MLPS?

 

That is correct.

That would be premature since you haven't yet checked to see if the relay is getting the signal to energize.

 

I believe I had this issue and replaced relay under the hood.

 

I think when it wouldn't start I swapped relays and once it started I bought new relays.

 

That's what I was driving at - this is really pointing to the MLPS more than anything else. You do need to chase where you are losing the 12 volts.

 

Since the OP hasn't bothered to return to the forum since he posted, it's probably irrelevant anyway, we're just talking among ourselves.

Exactly. This is why troubleshooting, not guessing, is recommended.

 

Thanks to all who responded to my question. I have been out of town and have not been able to respond until today. Well, I have checked all contacts and fuses. It appears to be a intermittent short in the starter relay. Many thanks to everyone for their input.

 

That would be a HIGHLY unlikely situation.