Not all the time. Changed the solenoid mounted on the fender by the battery. and a starter. Still does it. Would a toggle switch on the small wire coming to the solenoid from the key/ign. switch show that the ignition switch is worn out after 30 years? Any one have any other ideas? Thanks for any help- Mike.

 

The Starter Relay(solenoid) on the inner fender should have a larger post with the battery positive cable on it and several other wires attached to that same post, this is the main power distribution of the truck(just FYI)

Then on the other larger post only ONE cable, to the starter motor, ONE cable..................ONE CABLE
Starter Motor also only has this ONE Cable attached

Then on the smaller post labeled "S" on the starter relay, there should be a red/blue stripe wire
This wire should ONLY have 12volts when key is turned to START, test it
Unhook it from the starter relay, put a test light or volt meter on the red/blue wire, and a ground
Turn key to START
You should see 12v
Release key and NO 12v

If you have 12v with key in RUN position then wire is sorted to 12volts somewhere, could be ignition switch, or safety switch

This safety switch is there to prevent starting "in gear"
On an automatic this switch is on the transmission, drivers side, called NSS(neutral safety switch), above shift linkage

On a manual it is the Clutch switch, its on the clutch pedal push rod in the cab,

 

Thanks Ron, I'll check the voltage on the red/blue wire on the starter relay when the key is turned on. I pulled the cable to the starter off the relay and the red / blue line wire. Checking the post for the starter cable showed hot. Assuming that would show a burned/closed contact in the relay. Replace the relay? Any idea what would cause it to stick ? Just old or could it be caused by any thing else? Thanks for your thoughts, Mike.

 

Starter motor draws 60-80amps when activated, which is ALOT, lol, so a relay for that many AMPs needs to have wide contact area and smooth surface, if all the AMPs try to pass thru a smaller contact area then it will heat up and WELD itself together, so when the relay is de-activated the spring inside can't separate the contacts so starter motor keeps getting the 12volts

Over time, and hundreds of startups, the starter relay contacts can get burnt areas, pits and spikes, and this can cause them to weld together

Failing Starter motor or bad cables can cause more AMPS to be needed, so Starter relays contact area AMP rating is exceeded enough to start melting surfaces, which causes the pitting and spikes