# GMC 6.0 Wont start when cold



## mycirus (Dec 6, 2008)

Okay Guys, 

This is a strange one. When its below freezing my truck will catch and then die right away when I try and start it. I thought it was water in the Fuel filter so put a new one one and it worked on 1 cold 19 degree morning so I thought that was it. This morning it does the same thing. If I try it for 5 mins, and then let it sit for 5 mins, it fires up and runs perfect. Im just wondering if there is something else to check. The truck runs perfect after you get it started. Just on those cold mornings its acting up. Could I have that much water in my tank that its in the filter again? I have tried 3 tanks with cleaners and dry gas as well. Let me know what you think. 

Bruce


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## CityGuy (Dec 19, 2008)

sounds like you need to hook a scan tool up and see if there are some codes stored in the computer.


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## mycirus (Dec 6, 2008)

Would there be codes if there was no check engine light?


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## ahoron (Jan 22, 2007)

If you floor it will it start?


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## affekonig (Aug 5, 2008)

Eh?

#PIP3317F: Diesel Engine Hard Start Temperatures Below Freezing - keywords additive cold filter freez fuel gel gelling LBZ LB7 LLY LMM no P0087 P0093 P1093 restriction temp temperature vacuum wax waxing - (Dec 11, 2008) 


Subject: Diesel Engine Hard Start Temperatures Below Freezing 


Models: 2006-2008 Chevrolet Express 

2001-2007 Kodiak, Silverado Classic 

2007-2008 Chevrolet Silverado 

2006-2008 GMC Savana 

2001-2007 GMC Sierra Classic, TopKick 

Equipped with the 6.6 LBZ LB7 LLY or LMM Diesel Engine 




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This PI was superseded to update model years. Please discard PIP3317E.


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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
A 6.6 diesel engine equipped vehicle may be brought in for a hard start/no start only when outside temperatures are below freezing.

The customer may state the vehicle started, ran for a short period of time, and then stalled out while in park.

If the vehicle is moved into a heated shop or garage the vehicle will start normally.

Recommendation/Instructions:
If a below freezing hard start/no start has been verified it may be caused by fuel contamination, poor fuel quality, fuel gelling, or fuel waxing.

Open the fuel filter drain and get a large fuel sample out of the fuel filter. If water is found in the fuel system it may be the cause of the no start or hard start condition. The water in the fuel tank will freeze and restrict the fuel flow. During the hard start/no start condition monitor the fuel system vacuum readings to diagnose the concern. Normal fuel system readings when cranking are 1 to 2 inches Hg (in/Hg) of vacuum. A frozen restricted fuel system can reach 10 in/Hg of vacuum or higher while cranking.

If no water is found in the fuel system check the fuel API reading with the Kent-Moore J38641-B. The fuel API on winter blend fuels is approximately 35 to 44 depending on the location of the vehicle. Fuel APIs below 35 to 44 (summer blend) would have a higher possibility of waxing. Monitor the fuel system vacuum readings to diagnose the concern. Normal fuel system readings when cranking are 1 to 2 in/Hg of vacuum. A waxed/gelled fuel system can reach 10 in/Hg of vacuum or higher while cranking. 

Below is a test to help pinpoint the area of restriction:

Disconnect the fuel supply line at the rear of engine connection. 
Install a hand operated vacuum pump (Kent-Moore J23738-A) to the chassis side fuel supply line. 
Apply vacuum on the line in an effort to draw fuel from the fuel tank. 
Note the vacuum required to pull fuel up through the fuel line. 
If the vacuum is greater than 5 in/Hg (typically 15 to 20 in/Hg) to pull fuel from the tank then the restriction is either in the chassis lines or fuel tank pickup. 
If the vacuum required to pull fuel from the fuel tank is lower than 5 in/Hg then the issue is on the engine side of the fuel system. In this case, follow the current fuel system diagnostics in SI. 
Note: This procedure must be completed in a timely manner (less than 50 min.) to find the root cause. If the vehicle is in a heated area for too long the test may not find a waxed fuel system. 

The newest version of bulletin 03-06-04-017 describes the use of fuel additives for water removal and cold weather operation. If large amounts of water or contamination are found in the fuel system follow the current SI procedures for Fuel System Cleaning.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


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## mycirus (Dec 6, 2008)

ahoron;705741 said:


> If you floor it will it start?


If I floor it it just cranks and doesnt catch. When I let up it catches for a second, then stalls. I did this about 3 times. Tried it regular about 6-10 times. Let sit for 5 mins or so, then started right up.

As for the other post, looks like a good test to do but is it the same for gas? That looks like diesel method.

Bruce


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## affekonig (Aug 5, 2008)

Ah, you were talking about water in fuel so I just assumed diesel. I'll look around. I found one that said something about sticking valves.

#PIP3146B: Crank No Start When Cold Due To Compression Loss - keywords cylinder cylinderhead extended hard head lifter loss - (Nov 9, 2006) 


Subject: Crank No Start when Cold due to Compression Loss 


Models: 2000-2007 All Passenger Cars with Gasoline Engines 

2000-2007 All Light Duty Trucks with Gasoline Engines 




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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Crank no start when cold. The engine may crank over very fast, as if there is low/no compression. It may also run rough for up to 5 minutes after starting the engine and may exhibit a P0300 DTC too. This may be caused by sticking valves due to fuel contamination. When the engine is cold, the compression on multiple cylinders may be at 0 PSI. The engine also may pop through the intake or exhaust while cranking and the spark plugs may be fuel fouled when inspected. Some engines may also experience valve damage or cam followers that are out of position as a result of this.

This condition will normally occur in specific areas of the country for a period of time and then it will no longer occur after the suspect fuel source has been consumed in that area of the country.

Recommendation/Instructions:
If the SI Diagnosis lead to a compression loss due to sticking valves, the following information may help:

If there is no sign of valve damage or cam followers that are out of place, perform the following procedure to free up sticking valves and to prevent the valves from sticking again. If valve damage is present or if there are cam followers that are out of place, perform engine mechanical repairs as necessary to correct the concern and then perform the procedure below to prevent the valves from sticking again.

Clean the fuel system by following the applicable "Fuel System Cleaning" procedure outlined in SI. 
Add fuel injector cleaner "GM Fuel System Treatment PLUS, P/N 88861011 (for U.S. ACDelco®, use 88861013) (in Canada, 88861012)" . . . see bulletin # 05-00-89-078A, to the fuel tank in the approved quantities. 
Refill the fuel tank using fuel from a high volume, high quality filling station. 
Clean the induction system using GM Top Engine Cleaner. Follow the directions on the can but DO NOT force the engine to stall since forcing the engine to stall with liquid Top Engine Cleaner could cause the engine to hydro-lock. 
Advise the customer to change fuel filling stations. They should use fuel from only high volume, high quality filling stations or they should use a Top Tier Detergent Gasoline if available. See 04-06-04-047F (U.S.) or 05-06-04-022B (Canada) for details regarding Top Tier Detergent Gasolines. 
Note: If the condition is not eliminated chemically, it may be necessary to remove the valves to manually clean the stems. 

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


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## JCI Trans (Oct 21, 2008)

it is possible to have stored codes without a check engine light come on. My mechanic cleared 2 lean mixture codes from mine when the intake was replaced. it is plastic and had warped, allowing the wrong air/fuel in and would give me a hell of a time starting on cold days. I would have the codes checked before you go too crazy, probably some kind of sensor. good luck!


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## CityGuy (Dec 19, 2008)

Not all codes will cause the check engine light to come on. I'd get a cheap scan tool for Gm vehicals at the local store best guess is 50 or so dollars. My best recomendation is to spend the extra couple hundred and get a better one. I have a 400.00 one and love it so do all my friends as they alawys are over getting their vehicals checked.


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## Sharper Edge (Jan 26, 2005)

Not to high jack your thread but I have the same problem with my 5.3 yukon. If you floor it and crank it it will start???


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## mycirus (Dec 6, 2008)

Well I just put some Sea Foam in. I will see what that does for me. At least I know I can get it started. Just takes about 10 mins. I have a really good local garage. I may have them scan it for codes and maybe tune me up. Its just a pain. Otherwise I love the truck.


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