Had enough with cold starts!

[Dean'o]

I've got a 02' and I am about ready to put a stick of dynamite under the hood! A couple weeks ago the truck started having trouble starting when temps were in the high 30's. It starts fine when plugged in. I checked the gpr and got voltage to it but nothing coming out, so I bought the stancor relay and installed it. The truck still wouldn't start when cold, so I called my mechanic and he said it had to be the relay. Come to find out the new stancor was no good, so he installed a factory replacement. Now I know I have a good gpr because it was starting fine after that in moderate temps. The other day I go to leave work and my truck is dead, batteries didin't have enough to turn the truck over. I knew the batteries were good because I tested them the day before, so I figure the alternator was shot. I took the alternator to have checked and I was right, so it's now good too. Tonight I go to leave for school and the truck cranks and cranks but won't start (wasn't plugged in). The mechanic said my glow plugs were good, but I need to check myself to make sure.So here is what I know:
1-GPR is good.
2-Glow plug wiring harness is new
3-Batteries are good
4-Alternator is good
5-I will assume the glow plugs are good until I check them this weekend
Why won't my truck start?

[HVAC SuperTech]

did you just assume your GP relay was good? are you getting voltage to the little wires on the top and bottom of the GP relay? Thats comming from your Key on source. if so, you sure youre getting voltage through it? if you measure across the 2 big terminals you should get 0.00 volts. If you get 12.xx volts, then your relay is bad again, well, as lomg as youre getting voltage to the relay to turn it on that is . Dont just assume you have a good GP relay. you already found out you have had something wierd going on with your electrical system.

[Dean'o]

I'll check it again to make sure when I can get to it, but pretty sure it's not the problem.

[HVAC SuperTech]

could be your CPS

[drummerboy]

had a similar thing and it was from an oil leak (NSP) and my oil level got low. It gets thicker in the cooler weather . Mine was to the point of not starting below 40* without being plugged in. So just a thought and a nice quick fix if it is to check oil levels. hope it you figure out the problem

(and feel free to just give me the truck instead of blow it up)

[Dean'o]

What's the CPS?

[Damaged82]

try new glow plugs, I replaced the ones in my brothers truck yesterday and my buddies today. a lot of issues when it gets cold. I had a pickup that every single glow plug was bad

[Damaged82]

and whats the cold crank amps on your batteries?

[highraven99]

and how old are the batterys? most battery tests only test a battery to a point that it would start a gasser, most of which dont have no where near the draw that our high compression diesels need.

[Damaged82]

mmhmm