ok here's my delima. when i turn the key on to let the glo plugs come on they do and the batt. voltage drops to zero! then the light goes off and the volt gauge goes up 10-12v
and then i go to start the truck and it barely turns over and i have to pump the pedal to get it to start.

i check the batts and the altenator they're fine and working.

so im pretty sure its in the glo plug sys. some where.

if someone could help that'd be great. i have a gm electrical wiring book that's 4" thick and service manual but i need a place to start.

 

anybody? why is it when the glo plugs are on the batteries drain?

 

I haven't forgot about your problem yet but I can't say I have a good answer for you. My number one guess would be your batteries but you tested them as good. Check all your connections on the bats glow plug solenoid and the alt. If none of them are the problem then the next place I would check is the glow plugs there self.

 

thanks. i've checked most of the major connections like the batts, alt, etc. just havent had time to finish the little ones. im assuming it is the glow plugs since they're original on a 151,000 mile truck.