Hello to the group. I have a 1997 F 150 with 4.6 liter engine with approximately 290k.

Awhile ago I replaced the starter with a re-built one from the shop last July.

I'm now experiencing an intermittent problem with the new starter not working. As I turn the ignition key to the START position, there is a noticeable sound (thump) coming from under the dash or maybe on the firewall. The starter will not turn. Most times, the starter will finally work with turning the key on and off and into the START position enough times. After that, the starter works until the next time it doesn't work. The starter contacts were checked by the shop and all appears tight.

When the starter does not work,connecting the firewall solenoid hot contacts together produces nothing. I replaced the firewall solenoid without effect today.

The battery and charging system appears OK. I find that the problem occurs most frequently in the morning after the vehicle has been sitting for awhile.

When the starter does not work, moving the gearshift lever from PARK to NEUTRAL does not help. It does not work in either.

Really looking for suggestions about where to look next. It appears to be a loose or poor connection somewhere.