Hard Starts in the cold weather

Moi · December 20, 2020

Help I’m having the same issue please help. What was the problem?

Morgan06 · February 15, 2021

If it is about -35 degrees outside, would a 2012 Chevrolet truck start, it sitting outside for 2 hours?

02 GMC 2500HD · March 17, 2021

Hi,

I know this topic is a bit old and there are already a few threads on similar issues, but it's happening to my truck now too.

A little history on my truck:

2002 GMC Sierra 2500HD SLT, extended cab, 4WD, 6 liter, automatic, snowplow package, 130,000 miles.

I bought it back at the end of November last year. I got it "for a song" because it had codes PO171, PO174, and PO300 and the owner just wanted to get rid of it. I found that the 171 and 174 codes indicated a vacuum leak and were caused by leaking intake gaskets and holes/cracks in the EGR tubing.

I changed out the gaskets with the steel Fel-Pro (not technically hard to do, just a pain for my back and remembering what goes where when putting everything back together), replaced the EGR tubing, changed out the spark plugs and wires, and put a new battery.

Cleared the codes and they never came back - truck never failed to start so far, even in -10 degree F temps.

Yesterday I tried starting it and it just cranks and cranks, almost catches, but doesn't. When it almost starts (but doesn't) the engine makes a weird sound - almost like a deep exhale or sigh. I've checked the fuel pressure with the key on (I can hear the fuel pump prime) and it's at 50 PSI, which I understand is within range for my engine (the throttle body is not "fly-by-wire," it actually still has a cable actuating the throttle blade), and almost no bleed down - the pressure stays up there for quite a while.

The security light doesn't stay lit (although it reminds me to change the oil), so I don't believe it is a VATS or Passkey issue.

I've tried starting it with my foot off and on the pedal, disconnected the MAF, re-connected the MAF, added gas to the tank so it's on half full, and even tried shooting starting fluid in the throttle body - won't start.

Any ideas or suggestions? I can be a little handy with engines (can follow instructions at least) and have some tools.

Thanks for all your help.

CamGTP · March 17, 2021

Pull a plug and wire and see if it's got spark.

If nothing then it may not have a good crank signal.

davester · March 18, 2021

Yeah, testing for spark, and perhaps check if the injectors are getting pulsed with a noid light (or something else that will tell you if they are getting a signal.

02 GMC 2500HD · March 18, 2021

Hi CamGTP and davester,

Thank you for your replies!

Wouldn't you know it - the truck started right up last night like nothing was wrong. Turn the key, barely any cranking time, and fired right up!

I was able to pull some codes: P0300 (Random Misfire) and P01637 (Generator L-Terminal Circuit).

I understand the P01637 is tied to the alternator (or the wires going to the alternator?), but I see the needle on the dash voltmeter is swinging past 14, which I'm assuming means it's charging the battery?

Does anyone know if the P01637 code would cause a no-start condition?

So I guess the next possible steps would be:

- Pull the alternator and get it checked. I have no idea if it's ever been replaced or if it's the original one.

- Replace the alternator anyway, since I have no idea if it's original.

- Check the wires going to the alternator - anyone have any idea how to check these wires and what I'm looking for?

One other variable in this equation might be the weather/temperature when I tried starting it last night - it was a bit warmer than the last time it wouldn't start - it was about 35 degrees F, as opposed to about 25. Would a +10 degree change make that much of a difference? But, the funny thing is it started right up a bunch of times previously when it was much colder (- 10).

I'd like to try and get this starting thing sorted out, because now I'm getting a little worried about the truck stranding me - especially if I have the bed loaded with stuff and/or towing something... Or, if I have the wife with me - I'd never hear the end of it.

Also, I intend to use this truck to snowplow my driveway next winter, and it tends to get a bit COLD in upstate NY when it snows...

I'll try to keep this thread updated, in case it helps others who may have similar problems.

Thanks for any thoughts, suggestions, and ideas.

davester · March 19, 2021

I would suggest only replacing the alternator if it tests as being bad. I would just put a voltmeter on the battery with the truck running, and see how the voltage across the battery terminals compares with the dash voltage. If it's 13.5V-14.5V, it's working fine. And it's not causing the no-start condition, short of not charging the battery at all, and that would be obvious... And I would check/clean the alternator plug and check the wiring for problems before replacing the alternator due to that P01637 issue.

Can't tell you what may be causing the problem for you, my '04 Sierra starts up fine at -35C. I'll plug in the block heater below about -25C or so when it sits overnight. I've considered putting a battery warmer on the battery, as that's more important for starting these engines now.

02 GMC 2500HD · March 19, 2021

Hi davester,

Thanks again for your reply. I like the idea of a battery warmer and will look into it.

It was 19 degrees F this morning and again, the truck started right up with no problems. The P0300 code is gone but the P01637 is still present.

However, the alternator was making a little noise and got louder with increased throttle, and I also noticed that the lights (interior and exterior) were pulsing slightly. They would get a little brighter with increased throttle, and would also continue to pulse slightly during idle. Not sure if this is related, but for my piece of mind I'm going to just replace the alternator and belt this weekend. Looks very easy to do.

At worst this doesn't fix the starting problem and I have more diagnostics to do. At best, it does fix the problem and I have a spare alternator that I can look into/learn about rebuilding.

Again, I'll try to keep this thread updated with my saga in case it helps others.

02 GMC 2500HD · March 22, 2021

Changed out the alternator and belt this weekend - it took about 15 minutes (only 2 bolts and 2 connectors - I wish changing out parts were always that simple) and the hardest part for me was getting the new belt in place.

I'm glad I replaced the alternator as I think the bearings are on their way out - when I spun the pulley it felt gritty. But I also noticed that the lights are still slightly pulsing, so it wasn't the fix for that. The belt looked OK, but I don't know how old it is.

Still no starting problems this weekend and I'm not sure what to do next, so at this point I'm just going to cross my fingers and wait until it happens again.

I'll update again when/if it does and post a fix if I find one.

davester · March 22, 2021

maybe take off the belt and test spin the idlers, most people don't check them...

and remember, the alternator isn't like the old-school ones, where it doesn't work and you just swap in another one. these ones use a separate computer to control it's power output, and the code you posted indicated the computer was having an issue controlling it.

Edited March 22, 2021 by davester

02 GMC 2500HD · March 23, 2021

davester,

Thanks for the heads-up about the computer and alternator!

Look like I got me some learnin' to do.

I'll also check all the things that spin with the belt - I noticed that the AC belt was missing (I didn't even think to check if the AC was working because it was November when I bought it - that was dumb of me) and the tensioner pulley wouldn't spin by hand. Not that I really care if I have AC or not in this truck, but I'll probably replace the tensioner and belt just for kicks and see if it does work.

Thanks again for the replies!

davester · March 23, 2021

before replacing the a/c belt, test spin the a/c pulley itself, as well as the "inner part" of the a/c pulley (the outer part always spins with the belt, the inner part spins when the clutch is engaged). Either/both parts can be seized, which may be why the belt is not on there...