03 Hummer h2 won't start in extreme cold
 

I live in Yellowknife, the truck was starting fine until we had a cold snap of -40 days, the truck just cranks over and won't start, truck has oil pan heater block heater and battery blanket, I checked all fuses and none are blown, you can ear the fuel pump prime, any idea why it's not kicking over? I took the vehicle into a warm garage for a few hours and then the truck started fine but had a wonky idle like it was struggling to idle the interior lights were like going dim and not dim, and when i move around the mas air it
Seems to affect the idle by moving the plug that clips
On?

How old is the battery. Low volts will cause all kinds of problems .
You might have one bad cell. Start at the beginning,
Fuel. Pump is running, will the engine crank yes or no.
A dim light when cranking sounds like a battery or ground problem.
Last is air flow , if all else is working fine. It would be interesting to try
A hot air gun into the air filter to see if warm air allows it to start. Mike

Well since you say it cranks over but still fails to start but once you got it an "warm garage" it started fine. I have heard about gas with excessive water in it freezing in the lines? I have never experencied it since Pennsylvania winters are 15-35 degrees, but I have heard of it happening.

Do you think this issue could be anything to do with the mass air flow being bad?

I have a similar problem.I changed the oil/filter and I washed it after to clean it up. Well, now everytime I want to start it I a tik,tik,tik...like the starter or battery is going bad, it wasn't doing it before. I had the battery chaeck by the dealer and is fine. After I started one time and runs is fine. I check the starter for loose cables or jsu rust and nothing. Will see what happen...

tick tick tick is usually a sign of a weak battery. Did you leave the key partly turned on while washing it?

No, it was completely out. I had the battery checked and they said it was ok. I took over last week for something else and they guy told that sounded like the starter or flyway, so I don't have any idea yet what it is.:cool:

If you suspect its the starter, just replace it. They are cheap and easy to get to and are a high wear item. I doubt its the flexplate.

All the things you mentioed here happened to mine, began from sitting for a few days in -40 and not starting, lights dimming etc so i charged up the batteries all the way and now it wasnt idling smoothly sort of like vibrating. I got my batteries checked they were fine, they jusy cleaned up the minor corrision on the terminals and when i restarted everything was back to normal.

I'm retouching my hood, once is out of the shop I'll look into the starter and replace it if needed.