Need Help with a solenoid issue, I think ... no crank, no start whatsoever. Replaced the starter solenoid, truck started, left on for about 10 minutes, turned it off and same problem came back = no crank, no start.
Please provide some much needed help. Thx

 

Seems the battery has the power to start the engine. The problem could be dirty connections where cables connect to battery .

Good move to remove those cables ,clean them,then put them back on and see if it will crank now.

 

Also clean the ground on your fender-mounted starter solenoid. It gets ground from the top bracket that's mounted to the fender.
Before cleaning get ohm meter and check resistance, ohm meter black to battery negative post, red to the upper bracket of your solenoid, how many ohm?

 

I didn't measure the ohms but when I turn the key to try to start it, I hear one ping each time I turn the key.

 

Just use your DMM and set the dial to measure resistance at 200Ω and get the reading.
If you don't know how or don't have a DMM that's okay but eventually you are wasting your own time on troubleshooting, if the ohm reading looks good you don't even need to spend further time and worry about poor ground, and just deep clean the fender where that solenoid bracket is mounted. To do further testing you will need to own a DMM (even a cheap one from harbor freight works fine) or learn how to use the basic functions.
Like hanky mentioned, you need to clean all terminals and the connections, your issue appears to be a bad wiring issue, including poor ground from the fender.
If the ground and terminal look good to you visually, there are quite a few tests to be done by a DMM. If the ground is bad or next to impossible to clean your fender, you can add-a-wire and run a brand new ground wire (8-12AWG recommended) from battery ground post or your frame to the base of your starter solenoid mounting bracket.

Additionally, check my signature below. Right now nobody has a clue what truck you have.

 

My truck is a 1978 Ford F150 with 360 engine 2WD auto transmission

 

Do you have a DMM yet? If you do but you don't know how to use it please send a screenshot of it here.
Another screenshot of your starter solenoid (should be called starter relay).

Then I can show you step by step what to test beside the ground.