I have seen brand new pmds go bad in a couple weeks, then the replacement of same brand last for years afterwards. No rhyme or reason, luck of the draw.
Remove and clean all the engine grounds, and battery cable ends. Rough grounds will really mess with pmd, and gm was kinda cheap with them in the first place.
Where and how is your pmd mounted? Do you have a spare for testing? Unfortunately a spare pmd for a 6.5 is like a spare tire- you just need one. After grounds are good, you normally swap in the spare pmd. If you have to buy one, then skip to the next 2 steps first.
Make sure you are getting good fuel pressure to the ip. Dont just crack the bleeder ontop of the filter, you need to know it is good coming out of the filter housing. You can open your water in fuel drain and see volume and hook pressure gauge there- no pressure gauge, at least thumb over the fitting test.
Go to home depot or the like and buy 1/4" diameter 6" long piece of clear tubing. Install this inplace of the fuel return out the front of the injection pump. A trapped bubble in the fuel is ok, but a stream of bubbles means air is sucking into the fuel system somewhere, it must be found and fixed. Air in the diesel will cause everything from running wierd to not running at all.
Leroydiesel.com sells lifetime warranty pmds, remote mouting kits,etc. best answer I did running fleets was mount 2 pmds on the truck. Use an old plug just to keep thr contacts clean on the spare. Then any problem, anywhere, anyone can just turn off engine (if running at all), move plug from one to the other and start it back up, and go.
With 2 lifetime warranty ones- you can keep driving the truck while the old one is in the mail for free replacement.
Fingers crossed it is a quick and easy fix.
