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Discussion Starter · #1 · (Edited)
I have an intermittent start-up problem with my 2017 Chevy Colorado Z71 (4x4) Diesel:

Conditions:
Usually mild temperatures (Highs 65-80 deg F, Lows 45-60) and relatively dry.
Before starting, I always wait for the instruments to cycle back-and-forth, and I check for warning lights or messages. There are no warning lights or messages before starting except the check engine light is on. The engine light turns off immediately after starting. No warning lights thereafter. No messages.
I always add DEF as required.
The fuel filter says it has 53% life remaining after 14,000 miles.
The oil/filter has been changed by Chevy service three times in 14,000 miles. The oil filter currently has 75% life remaining.
The air filter was changed once at about 9,500 miles.

Symptoms:
A “Pop / Clunk” sound, combined with a slight “Stumble,” occasionally occurs as the engine catches on start-up. The “Pop / Clunk / Stumble” occurs usually just once, but sometimes twice; very quickly. This sound/stumble only occurs during about one-in-4 start-ups. It does not seem to matter if the start-up is the first one of the day or the last one with a warmed-up engine. I have been to Chevy service twice, but they have been unable to replicate the sound/stumble on startup and cannot figure out what is going on. On the other hand, I can replicate the sound/stumble during about 20-25% of my startups. I am careful to make sure that I keep the ignition key fully engaged during startup. (I am sure that I am not releasing the ignition key too early.) After starting, the engine runs fine with no warning lights or messages. (Exception: Cold, 20-degree weather requires some throttle to keep the rpms over 900 rpm during warm-up, but there are no warning lights or messages showing.)

My Colorado diesel has a little over 14,000 miles on it now (a couple of long trips through the intermountain west). This occasional “Pop / Clunk / Stumble” on start-up did not exist at all for the first 11,000 miles. The problem started about six weeks ago when the truck was briefly subjected to some cold/snowy weather (evenings down to as low as 22 deg F in Ely, Nevada for about four days) and possibly some questionable diesel fuel (too much biodiesel and/or some water in the fuel?). I have recently been very careful about finding “good” diesel (low biodiesel content and good service stations/tanks), and this seems to have helped reduce the severity of the “Pop / Clunk / Stumble” somewhat, but it is still there occasionally. I’ve run at least five full, “good” tanks of diesel fuel through the truck since the problem started. Also, I recently added some Howes diesel fuel treatment during my latest fill-up, but the treatment does not seem to be helping; not yet anyway.

Note: When the truck was subjected to low temperatures overnight (22-30 deg F) for a few days, I never saw the glow plug indicator (wait-to-start light) come on first thing in the morning with the ignition switch turned to “ON/RUN”; before starting. I did get the “Pop / Clunk / Stumble” upon start-up. These cold starts were problematic. I had to keep a little throttle on to keep the rpm above 900 rpm (and below 1,100 rpm), or the engine would stall/stop. At first, the engine would surge between about 700 and 1,000 rpm for a minute or so. Does anyone have any actual experience relative to what ambient temperatures trigger the glow plugs? Has anyone else experienced a similar cold starting problem?

Well, anyway, I know this intermittent “Pop / Clunk / Stumble” on start-up is abnormal; particularly since I am still experiencing it during nice weather, and I did not experience it at all during the first 11,000 miles. Therefore, I am wondering what might be causing this occasional start-up problem and how I might go about eliminating it. Any ideas?!

Thank You,

Arizona (and Southern California) Bill
 

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Sounds like you may have gotten some bad fuel. I would take a look at the fuel filters as a start - they are easy to change and not expensive.
 

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hmm I always see a glow plug indicator on stone cold starts for atleast a couple seconds. If you ran bio diesel I believe in the manual it say it will clog the emission stuff.
 

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It's been in the 40's here in Michigan and I see my glow plug indicator on for 2-3 seconds when I start my truck cold every morning. It pops on for a quick second in far warmer ambient temperatures as well. Kind of makes me wonder if something's not working 100% with your glow plugs.
 

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I have an intermittent start-up problem with my 2017 Chevy Colorado Z71 (4x4) Diesel:

Does anyone have any actual experience relative to what ambient temperatures trigger the glow plugs? Has anyone else experienced a similar cold starting problem?

The only time I have seen the glow pugs not run on start up after the engine has cooled over night is in the middle of the next day when it is 95+ outside. To me it sounds like you have a leak in your fuel line somewhere and the line isn't being pressurized properly on start up. It may not be an external leak, but an internal leak from a bad/misaligned seal and the fuel is slowly flowing back into the tank. Next time you try starting, turn the key to the on position but don't start the vehicle, and this will pressurize the line and push the air out. Then try starting the engine like you normally would and see if the noises disappear on start up.
 

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Did you ever figure out what was causing this? Mines doing it and thought it just needed a fuel filter change but it started doing it again
Hey man, I don't see any replies to you from this guy. Did you find out what your problem was? I'm also getting the same thing on my 2016. No one has been able to diagnose the issue. I've been dealing with this all winter
 
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