2007 GMC Denali stalls after towing

[mark harris]

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.

Good to know, I have a 08 6.2 haven't done any towing

 

[wesyder]

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.

Great info, i was experiencing vapor lock on my 05 as well but it would stall while driving, my 08 stalls when i come to a stop, I thought it may have been the cats getting too hot, i added trans coolers and low temp thermostats for towing and haven't had any more issues with either


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[alpha_omega]

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.

Jeff, what kind of insulation and tape did you use for your fuel lines? Did you happen to take any pictures? I figured you probably didn't wrap them with foam insulation considering the heat coming off the engine and tranny, so I was wondering if you used something with a foil backing or just wrapped it with some foil tape (used in HVAC) to keep it from melting. I had a very similar issue last summer and haven't had my Yukon running since. I'm hoping by doing your fix along with the relay, CS position sensor and a tranny cooler it will get her back on the road. Thanks for the info!

 

[JEFFC]

Jeff, what kind of insulation and tape did you use for your fuel lines? Did you happen to take any pictures? I figured you probably didn't wrap them with foam insulation considering the heat coming off the engine and tranny, so I was wondering if you used something with a foil backing or just wrapped it with some foil tape (used in HVAC) to keep it from melting. I had a very similar issue last summer and haven't had my Yukon running since. I'm hoping by doing your fix along with the relay, CS position sensor and a tranny cooler it will get her back on the road. Thanks for the info!

I used a heat shield that is a high heat rubber with insulation on the inside, you can do a search on ebay for fuel line heat shield and you will see it. I used the red or rust color in a 3/4" to wrap the fuel line and the black color in a 1 1/2" for the fuel rail. The fuel rail took a lot of cuts and zip ties. I have a 2015 wakeboard boat that has the same red insulation on the fuel line from the factory.

 

[Keola62]

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.

Hi JEFFC,
I am curios what valve or bleed off hose you used.. Do you have any pics?

 

[kbuskill]

Hi JEFFC,
I am curios what valve or bleed off hose you used.. Do you have any pics?

He is referring to the shrader valve on the fuel rail. It is a test port for hooking up a pressure gauge and should have a plastic cap that screws on to it kinda like a valve stem on a tire.

 

[blenius]

I have an 07 Yukon xl denali that just turned over 150k miles and started stalling at a stop this spring. It only happens when I pull my camper (18ft) ~50miles or drive the vehicle itself ~100mi. We have had it into several shops, including the dealership who tells me there's nothing wrong with it, and replaced tranny cooler lines, air filter, battery, crankshaft sensor, camshaft sensor, fuel pump, and fuel pump relay. Just tried the bleeder valve trick and determined that it is vapor locking, even though the dealership swears that it isn't possible.

Just wondering if JEFFC or anyone else that has had success from the heat taping has any pictures of the exact areas they heat taped just to make sure that I will get adequate coverage of the problem areas. I love this SUV so much, and especially after all this time and money I just want it fixed!

 

[mark mitchell]

I have a 2008 Yukon Denali with the 6.2 and have had the same issue, twice, but only when towing my big 31' camper. No issues towing smaller loads. The dealership agreed this is a vaporlock issue, they actually suggested wrapping fuel lines as JEFFC suggested, but of course they want $400 to do it, so ill be doing it myself. They did also suggest running premium to help with vaporlock, not sure if anyone has any info as to running premium and if that can help?? It would be nice to see some pictures of others that have wrapped their lines and had success getting rid of this issue by doing so, as im not sure yet where the fuel line is near the transmission. I plan to work on mine this weekend, before we head out camping again in 2weeks. Ill post up pics if no one else does of what I did, then I can update after we tow our camper to see if it fixes the issue for us.

 

[mark mitchell]

I have an 07 Yukon xl denali that just turned over 150k miles and started stalling at a stop this spring. It only happens when I pull my camper (18ft) ~50miles or drive the vehicle itself ~100mi. We have had it into several shops, including the dealership who tells me there's nothing wrong with it, and replaced tranny cooler lines, air filter, battery, crankshaft sensor, camshaft sensor, fuel pump, and fuel pump relay. Just tried the bleeder valve trick and determined that it is vapor locking, even though the dealership swears that it isn't possible.

Just wondering if JEFFC or anyone else that has had success from the heat taping has any pictures of the exact areas they heat taped just to make sure that I will get adequate coverage of the problem areas. I love this SUV so much, and especially after all this time and money I just want it fixed!

My 2008 has just over 150K miles also, wonder if this issue is related to higher mileage engines for some reason??

 

[Jedig33k]

Any updates on this? Did everyone's issue get fixed by wrapping the fuel lines? My Theory is oil.

I ran my trailer up and down the mountain most of the Spring with no issue, but I started having this same issue around mid summer (About 2 tows in). I thought Fuel, most though CATs, and after a CAT test and $3K worth of repairs (fuel pump, and crank shaft position sensor) on an 07 Denali 6.2, I took it into the quick lube and realized this was the second oil change of the year, and I have been driving this thing HARD. It unfortunately was at the end of the season for us here in Idaho and I stored the trailer. I have not changed the oil (since the Yukon has not informed me to yet) since early fall. I figure the oil is pretty dirty, so I may go pull the trailer out of storage and take it up the mountain and see what happens. It is a test and I have not found anyone telling me that old dirty oil would cause this, but I have a hunch.