2007 GMC Denali stalls after towing

[mjrasmu]

I have a 2007 GMC Yukon XL Denali. I tow often with this vehicle and I have had very few problems until recently. It has stranded my towing my boat on 3 different occasions the last few weeks. After I pull for about 30 minutes if I come to a stop it simply just dies and will not start again for about 1-2 hours. I have replaced the fuel pump and the oil pressure sensor. It does not throw any codes or anything. I am at a loss on what it could be. I have read another forum that says it could be a water pump causing low water pressure, but this seems like a stretch to me. Any ideas? Any help would be appreciated we would like to go boating again for July 4th, but can't if I don't get this fixed.

Thanks,
Mike

 

[TowGMC]

I would think it has to be fuel delivery related. You replaced the pump but have you checked fuel pressure both before towing and then again when you have the problem?

And I'm gonna to out on a limb here.... as silly as it sounds, when you have this problem have you tried pulling the fuel cap off? My old 3/4 ton Suburban had a problem with vapor locking when pulling a long grade pulling my then 8,000 lb trailer. When I'd pull the cap off there would be a loud hissing. On one trip I just drilled a small 1/16" hole in the cap to relieve the pressure and it worked fine until I had a chance to get a new cap. But that was an old 8.1L engine.

 

[mjrasmu]

Thanks for the ideas. I haven't tested the fuel pressure when this happens. I plan on trying that on Saturday after I have replaced the Crank Shaft Position Sensor. Also, on this last incident I did relieve some pressure at the fuel rail and it fired up after about 30 minutes instead of a couple of hours. I do feel like it is vapor locking but not sure how exactly to diagnose that and even so once I have diagnosed it, how to repair it.

I will try the fuel cap trick if it happens again, which I pretty sure it will.

 

[jagi0966]

Mike...any news here?

I had the same issue this past weekend. Was towing a 24ft Camper and came to the end of the exit ramp, engine stalled. Crank, but no start. After about 20 minutes it started. 2008 Yukon Denali.

Coolant temps were running hotter than I think they should as well. Was running in mild hills around 65mph and the coolant temp would go to the 220 area or so. Never overheated, but I havent towed that big a load in a couple years. Even though it was 85F outside, I thought it easily would have held the standard straight up gauge position of 210F. I wasnt pushing my foot in it much at all.

Other experiences?

Thanks,

Dean

 

[mjrasmu]

Dean,

I tried a couple of things and I'm not sure which one did the trick, but I have pulled my boat twice without any problems. Both fixes where super inexpensive if you do them yourself. First, replace the Fuel relay, it is in the relay box under the hood on the drivers side. Second, replace the crank shaft position sensor, you have to access this through the passenger side wheel well. this is a little more difficult but a reasonable at home mechanic can do this job. The crank shaft position sensor in my Denali had some oil in it which could have easily contributed to the problem. Good luck and I hope this helps.

Mike

 

[jagi0966]

Good info Mike. Did you have any trouble codes for the crank position sensor at all?

Thanks!

Dean

 

[JEFFC]

Not sure if anyone is still having this problem but I finally figured it out. Let me know if interested what the cure was for me.

 

[tgui]

Not sure if anyone is still having this problem but I finally figured it out. Let me know if interested what the cure was for me.

Please post your fix!

 

[NateDiggity]

I had this exact same happen on a different vehicle (still GM though) and it was the crankshaft position sensor. It would get hot, screw up, and tell the computer the crank wasnt spinning so it shut down the fuel injectors. After it cooled down, it fired up and ran fine.

At least thats where I would start, I remember it being about ten bucks and one bolt

 

[JEFFC]

Please post your fix!

I have had my 2007 Denali 6.2L since new and never had a problem until last summer. It developed the same problems as others are having. When coming to a stop after towing in hot conditions, it would die and not restart for about 30 minutes. It was very hard to diagnose because it was impossible to duplicate the problem at a shop. My mechanic hooked up his Snap On Scan tool with live data, a fuel pressure gauge and I hooked up my trailer on a hot day and headed up the pass. When I pulled to the side it failed and would crank but not restart. I had good fuel pressure, crank signal, coil signal, injector pulse. Basically everything it needs to run so I was stumped. I got out to disconnect the fuel pressure gauge and this is when I discovered the problem almost by accident, boiling hot aerated gas came shooting out of the bleed off hose. I turned the key to on and bled fuel a few seconds until no bubbles appeared and the engine fired immediately. I then headed back up the pass and duplicated the failure 3 more times, each time starting up after bleeding fuel. I cured the problem by wrapping the fuel rail with insulation and also wrapped the fuel lines where they get close to the transmission and up the back of the engine leadin to the fuel rail. it has never failed since even towing on days over 102 degrees.