ok i have a 2002 f150 4.2l 4x4 5spd manual... about a week ago i went to start my truck,fired right up but sounded odd so shut it down to the starter still cranking the engine, after about 6 or so seconds it stopped, so coast started to get home. pulled starter and had it tested and test came back as good/proper, replaced firewall relay/solenoid and it fixed the problem, for a couple days, now its right back to doing it again.. ould i have fried a new relay/solenoid that quick or does it sound like i may have bigger issues?? until i figure it out i was going to throw a kill switch between starter and battery to kill starter if it acts up i can just cut power and keep engine running. thanks for any help

 

In the starter is a second power solenoid that makes contact to pass battery to the starter AT THE SAME TIME throws out the starter gear to engage the flywheel.
This engagement is what you heard. Not good for the flywheel teeth.
Likely need a replacement starter if the contacts are burning closed or something is sticking..
Good luck.