[John L Williams]

The headhunter pumps runs up to 58 psi then runs for a minute or so then cycles off and the pressure drops to 30 psi and immediately starts running again. It does this repeatedly until it shuts off due to overheating.
The 12 volt pump runs ok, pumps to 35 psi and cycles on and off properly.
The headhunter pump was running ok until I filled the water tank through the tank fill at top of tank. It started cycling right after.
Any suggestions?

I had problems with mine doing the same thing, but it was a combination of air in the lines, and the "city water" valve was open..