I have just replaced my weak GP, starts fine runs fine. After a twenty mile trip, I shut down for fuel, tried to restart, nothing. Weird feed back through speakers, VM says 8 or less.. And the Relay number two under the hood was clacking, this controls IDM. I waited a few tried again, same thing, even swapped relays around, this time I waited a few minutes with igntion on and tried suprise it turned over and reluctenly started. I got home check voltages all looked good so tried to start same thing. So shut off ignition did some poocking around, tried again this time good voltage and good turn over, no start. Stop and tried one more time and started just like normal two turns and running. Any Ideas? Or trouble shooting Ideas? Oh I do have clean cables starter has been replaced in last six months.

 

Load test the batteries. Most Autozones will do it for free. These engines need all the power 2 batteries can give it. The IDM will act screwy if if battery voltage is too low. ie. 10.5 volts IIRC.