Alright so the other day my jimmy started up perfectly fine in the morning. It was about 36 degree. Later on I went to go start it but it wouldn't start, the lights are on, dash lights, and radio are all perfectly fine. When I go to start it I can hear the pump engage and when I turn it full I can hear the reley in the glove box, but no cranking. After awhile of constantly going back to power on into start it finally starts to crank and start. I dismissed it as it could be a minor hiccup.

So about a week later is about 20 degree and it starts fine but does the same thing after I get to work. But later on in the day its even colder, about 15 degrees. I spend an hour trying to get it to start the way I did before no luck. But all the lights and everything where fine. Call my brother down to see if a jump night help. About 7 minutes in the cables still wouldn't start until I tried cranking it after he pulled the cables off and it finally started to crank. And I get it home.

Today being even colder between 5 to 0 degrees and colder later tonight it doesn't crank at all but lights and everything are still on when I out the key in or open the door.

So what could be wrong? Can it be my Battery's CCA? Its 660 CCA and I just got it about 6 months ago, I do admit this battery does look smaller than my older one. Just changed all my spark plugs about 3 months ago. And changed the oil last week. I also read it could be a possible Crank Shaft Sensor? Any help is greatly appreciated

 

Doesn't sound like the battery or the crankshaft sensor to me. I would make sure all of the electrical connections under the hood are clean and tight while you are waiting to hear from those more in the know than I. You might also want to share more information about your Jimmy, i.e. 2 vs 4wd etc...

 

Its a 1996 GMC Jimmy 2-Door RWD to 4WD. It has a 4.3L V6 Vortec.