Looked at previous threads but didn’t see one matching my problem. Starts just fine 99% of the time, then for no apparent reason I turn the key lights come on, but nothing but very light click-no crank. Checked starter, new battery, looks like voltages getting to starter and solenoid. I’ve heard rumors of grounding problems at the starter. Tried tightening things there in spring this year but nothing seemed to move-probably corrosion welded. It seemed to be better over summer, but now going into cold wet/cold frozen the problem is back. Had one case of hundreds where holding key in ignition position for 15 seconds, the starter suddenly kicked-no weakness, just turned over like it should have 15 seconds earlier. Ideas welcome!
You may need to have the start trigger circuit looked at. Some older cars ran the trigger circuit straight from the switch to the solenoid without relays. I think most newer cars and trucks use a relay now. One advantage is the ability to interrupt the circuit easier with the security system. Another is to reduce high-amp strain on the ignition switch. Either way, your symptoms sound like a relay on the fritz.
Something else to check is the starter inhibit switch. If this is an automatic, try moving the shifter to neutral and back to park while holding the key to the start position. If this is a stick shift, hold the key to start and cycle the clutch pedal up and down a couple of times to see if the problem is there.
Hopefully that helps narrow down the problem.
Wish I’d thought of these. I’ll check. Both sound like good possibilities. Thanks.
Happy new year. I saw this twice already and it was the connector at the starter that was looking ok but badly corroded. In one case when trying to clean the connector it just broke in the hand of one of the guys I work with.
I had a similar problem on an older F150 and it turned out to be the main ground wire. It turned out to be a slightly corroded and loose (ground) wire where it was attached to the chassis. Easy to check.
Do '01 F150s have factory security systems from the factory, PATS? If PATS, is that little LED flashing while you try to start it?