2007 GMC Denali stalls after towing

[kbuskill]

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 (fule pump, and crack shaft positions 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.

Certainly not knocking you testing and trying to figure this out.

But out of curiosity, what is your theory about the dirty oil?

What do you think it may be affecting?

 

[wesyder]

Just my experience but i put tru cool trans coolers on both of my trucks and haven’t had this problem since


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[Jedig33k]

Certainly not knocking you testing and trying to figure this out.

But out of curiosity, what is your theory about the dirty oil?

What do you think it may be affecting?

So, my thinking goes along the lines of this. Basically, bad oil causes engine heat, engine heat will be seen by the sensors (Typically)

Now for a story. Pulling the summit one hot summer day my 07 Yukon XL started all the bells and whistles and told me to pull over as she was shutting down ... and she did for an hour. The issue was failed fan in the double electric radiator system, but only when it had to run in high mode. Otherwise both fans worked fine and I could drive all day around town, but once I towed and both high fans were required, I overheated quickly and the sensor found it.

Again, dirty oil causes engine heat, but more of an all over warm cozy heat unlike that of a OMG I need cool water heat!!!

My tip-off (and again I have NOT proven my hunch) is the replacement of the so called bad crankshaft sensor. If you look up the "symptoms" of a bad cs sensor, you get the following.

"The most common failure for one of these sensors is when the engine is idling it will just stall. This is because the pulse width is at its widest gap because of the slower engine speed. Heat will also cause the sensor to fail because of the thin wire winding which will expand with heat and short out to one another changing the sensors resistance which will cause the sensor to stop giving a signal to the main computer. Once this happens the pulse generation to the injector and ignition systems will stop the engine from running." source: https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor (and random google search).

So, while it could be the fuel (aka vapor lock) I have been told again and again that it does not happen in newer vehicles. I am not ruling it out, but I have not seen many people come back and say wrapping the fuel lines worked. Did it?

My theory (or wild guess) is it really has to do with the older Chevy/GMG trucks and how they handle dirty oil. With all the safety features built in to these trucks, I think it is a bug in how the sensors work. Assuming a 150K truck sensor handles the oil/heat mathematics the same as it did when the truck was new vs when all the seals start to break down... you have a safety first equation that just shuts it down until safe.

 

[Jedig33k]

Just my experience but i put tru cool trans coolers on both of my trucks and haven’t had this problem since


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Why would the heat of the Transmission shut down the Engine? Please tell me your situation and how it worked?

 

[wesyder]

Why would the heat of the Transmission shut down the Engine? Please tell me your situation and how it worked?

The issue is caused by vapor lock, there are 2 extreme heat sources in the area of the fuel lines, the catalytic converters and the heat from the transmission, although I couldn’t do anything about the cats however i did reduce trans temps significantly, not knowing if it would solve the stalling I didn’t like seeing my trans temps that high and wanted to upgrade the cooler, I have not had an issue since, my situation consists of pulling grades towing roughly 6k lbs in 110 degree temps

 

[Jedig33k]

The issue is caused by vapor lock, there are 2 extreme heat sources in the area of the fuel lines, the catalytic converters and the heat from the transmission, although I couldn’t do anything about the cats however i did reduce trans temps significantly, not knowing if it would solve the stalling I didn’t like seeing my trans temps that high and wanted to upgrade the cooler, I have not had an issue since, my situation consists of pulling grades towing roughly 6k lbs in 110 degree temps

Can I ask your vehicle model and year? Also, what temps were you seeing? I typically flip my computer over to watch my tanny heat and have not really seen it go above normal. The stock tranny cooler seems to be working fine, but you upgraded yours ans saw better results?

 

[wesyder]

Can I ask your vehicle model and year? Also, what temps were you seeing? I typically flip my computer over to watch my tanny heat and have not really seen it go above normal. The stock tranny cooler seems to be working fine, but you upgraded yours ans saw better results?

2005 xl denali with the 6.0 and a 2008 escalade esv with the 6.2, both awd...before in stop and go traffic 90 degree day not towing trans temps would creep up to about 250 degrees on my 05, with the new cooler it hasn’t gone over 200 degrees regardless 110 deg day pulling a grade towing my boat at 70 purposely trying to overheat it, it was a no brainer to add it to the escalade.. denali has roughly 280k. miles the escalade has roughly 150k neither one has stalled since, just my experience


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[Jedig33k]

2005 xl denali with the 6.0 and a 2008 escalade esv with the 6.2, both awd...before in stop and go traffic 90 degree day not towing trans temps would creep up to about 250 degrees on my 05, with the new cooler it hasn’t gone over 200 degrees regardless 110 deg day pulling a grade towing my boat at 70 purposely trying to overheat it, it was a no brainer to add it to the escalade.. denali has roughly 280k. miles the escalade has roughly 150k neither one has stalled since, just my experience


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Probably my last question for you. I assume your rigs had OEM Tranny Coolers, did you find these not sufficient, so you fully replaced them with new ones?

 

[wesyder]

Probably my last question for you. I assume your rigs had OEM Tranny Coolers, did you find these not sufficient, so you fully replaced them with new ones?

No worries yes they did have oem coolers, i upgraded to bring the trans temps down, didn’t know it would solve my stalling problems as well


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[JEFFC]

So, my thinking goes along the lines of this. Basically, bad oil causes engine heat, engine heat will be seen by the sensors (Typically)

Now for a story. Pulling the summit one hot summer day my 07 Yukon XL started all the bells and whistles and told me to pull over as she was shutting down ... and she did for an hour. The issue was failed fan in the double electric radiator system, but only when it had to run in high mode. Otherwise both fans worked fine and I could drive all day around town, but once I towed and both high fans were required, I overheated quickly and the sensor found it.

Again, dirty oil causes engine heat, but more of an all over warm cozy heat unlike that of a OMG I need cool water heat!!!

My tip-off (and again I have NOT proven my hunch) is the replacement of the so called bad crankshaft sensor. If you look up the "symptoms" of a bad cs sensor, you get the following.

"The most common failure for one of these sensors is when the engine is idling it will just stall. This is because the pulse width is at its widest gap because of the slower engine speed. Heat will also cause the sensor to fail because of the thin wire winding which will expand with heat and short out to one another changing the sensors resistance which will cause the sensor to stop giving a signal to the main computer. Once this happens the pulse generation to the injector and ignition systems will stop the engine from running." source: https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor (and random google search).

So, while it could be the fuel (aka vapor lock) I have been told again and again that it does not happen in newer vehicles. I am not ruling it out, but I have not seen many people come back and say wrapping the fuel lines worked. Did it?

My theory (or wild guess) is it really has to do with the older Chevy/GMG trucks and how they handle dirty oil. With all the safety features built in to these trucks, I think it is a bug in how the sensors work. Assuming a 150K truck sensor handles the oil/heat mathematics the same as it did when the truck was new vs when all the seals start to break down... you have a safety first equation that just shuts it down until safe.

 

[JEFFC]

In response to Jedi33g above post. It really sounds like we have 2 different problems. My problem happened without the engine or transmission being over heated. You did not mention if your Yukon is a Denali, if it is not, you do not have the same engine or transmission as the owners of a 2007 and newer Denali or Escalade. You have been misinformed about vapor lock on newer fuel injection systems. They do vapor lock and have more tendency to do this than earlier injection systems. The reason that newer systems are more likely to vapor lock is because there is no longer a return fuel line from the fuel rail to the tank. With the return line systems, cool fuel was always circulating through the fuel rail and being returned to the tank. Go back and read my post about how this problem was diagnosed, all sensors were operating correctly, the only thing found not normal was the boiling hot fuel that was bled out of the fuel rail. (vapor lock) That immediately corrected the no start condition.

 

[JFitz]

Hi everyone - I simply had to join since this thread is just too similar to what I've been encountering.

I have a 2007 Yukon Denali that has similar issues. Three times, it has stalled on me after slowing down and stopping at a light after cruising at highway speeds. The first two times it happened while towing, but the most recent time was just the vehicle. All three times I had to have it towed (once to dealer, twice to my local mechanic).
- Stalled after decelerating to a stop after highway speeds. No shuddering or sputtering. Just died.
- Engine would crank over, but not fire
- Plenty of fuel
- New battery (less than 6 months old).
- No error codes - no CEL, and no codes afterwards.
- In all three instances, the mechanic was able to start the vehicle (after sitting for a while) - no issues seen, vehicle ran just fine.
- Mechanic drove vehicle around over several days with diagnostic tool connected - all systems looked good, no error codes.

To try to troubleshoot this issue, I have been reading up on this. One item that seems to come up frequently is the role of the oil pressure sensor (OPS) in powering the fuel pump. Many people have had OPS issues, mostly reading as zero or fluctuating oil pressure gauge. It looks like the OPS has a second function which is to also power the fuel pump (in addition to the fuel pump relay, which energizes the pump at startup to pressurize the system). To diagnose this, I pulled the relay while the engine was running (both at idle and also at ~ 3000 RPM) and the engine sputtered and stalled (although it threw an error code when I did this). This would leave me to believe the OPS is not doing it's job (if it is supposed to, that is).

Does anyone know if the OPS does in fact play a role in powering the fuel pump?

Otherwise...I'll be following this thread closely. When I get a chance I'll do some more driving and see if I can nail down what may or may not be happening. The lack of a logged error code is maddening. I'll watch the transmission temp, engine temp, pay more attention to the fuel pump priming, and also see if I can get a fuel pressure gauge somewhat inexpensively to keep in the car and test the pressure if/when it happens again.

 

[wesyder]

Hi everyone - I simply had to join since this thread is just too similar to what I've been encountering.

I have a 2007 Yukon Denali that has similar issues. Three times, it has stalled on me after slowing down and stopping at a light after cruising at highway speeds. The first two times it happened while towing, but the most recent time was just the vehicle. All three times I had to have it towed (once to dealer, twice to my local mechanic).
- Stalled after decelerating to a stop after highway speeds. No shuddering or sputtering. Just died.
- Engine would crank over, but not fire
- Plenty of fuel
- New battery (less than 6 months old).
- No error codes - no CEL, and no codes afterwards.
- In all three instances, the mechanic was able to start the vehicle (after sitting for a while) - no issues seen, vehicle ran just fine.
- Mechanic drove vehicle around over several days with diagnostic tool connected - all systems looked good, no error codes.

To try to troubleshoot this issue, I have been reading up on this. One item that seems to come up frequently is the role of the oil pressure sensor (OPS) in powering the fuel pump. Many people have had OPS issues, mostly reading as zero or fluctuating oil pressure gauge. It looks like the OPS has a second function which is to also power the fuel pump (in addition to the fuel pump relay, which energizes the pump at startup to pressurize the system). To diagnose this, I pulled the relay while the engine was running (both at idle and also at ~ 3000 RPM) and the engine sputtered and stalled (although it threw an error code when I did this). This would leave me to believe the OPS is not doing it's job (if it is supposed to, that is).

Does anyone know if the OPS does in fact play a role in powering the fuel pump?

Otherwise...I'll be following this thread closely. When I get a chance I'll do some more driving and see if I can nail down what may or may not be happening. The lack of a logged error code is maddening. I'll watch the transmission temp, engine temp, pay more attention to the fuel pump priming, and also see if I can get a fuel pressure gauge somewhat inexpensively to keep in the car and test the pressure if/when it happens again.

I don’t believe the OPS controls the fuel pump but simple enough unplug the sensor and see if the truck runs, I’ve done a few of these sensors and the trucks were always able to drive to me, and like you said there was a code stored related to its failure


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[JFitz]

I don’t believe the OPS controls the fuel pump but simple enough unplug the sensor and see if the truck runs, I’ve done a few of these sensors and the trucks were always able to drive to me, and like you said there was a code stored related to its failure

Thanks. I'll try what you suggest - it's really tucked way up close to the firewall but I'll see if I can get it disconnected. You mentioned that you've done a few of them - have you removed everything (i.e. intake manifold) to get to it? Or did you manage it otherwise?

 

[wesyder]

Thanks. I'll try what you suggest - it's really tucked way up close to the firewall but I'll see if I can get it disconnected. You mentioned that you've done a few of them - have you removed everything (i.e. intake manifold) to get to it? Or did you manage it otherwise?

No, i can replace the sensor without removing anything except the engine cover


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[JFitz]

No, i can replace the sensor without removing anything except the engine cover

Good to know. I can get my hand on it...but it's really tucked in there. I'll take your advice and unplug it and see what happens, and then go from there.

 

[puckhead]

Same issue here. I just got done changing the thermostat and flushing the coolant system. I already have an auxiliary transmission cooler that helped with another issue. I don't want to throw money at this all willy nilly. I think I will try the insulation tape on the fuel lines next. I do have a faulty oil pressure sensor but the truck runs fine most of the time, except when it overheats. No towing here, just lots of mountain driving. I am also thinking of removing the Cat, don't know if there are sensors on it though.

 

[swathdiver]

Same issue here. I just got done changing the thermostat and flushing the coolant system. I already have an auxiliary transmission cooler that helped with another issue. I don't want to throw money at this all willy nilly. I think I will try the insulation tape on the fuel lines next. I do have a faulty oil pressure sensor but the truck runs fine most of the time, except when it overheats. No towing here, just lots of mountain driving. I am also thinking of removing the Cat, don't know if there are sensors on it though.

Andy, you have several catalytic converters with sensors to monitor their performance. Hollowing them out will trigger check engine lights. There are fixes for this however.

 

[swathdiver]

...the only thing found not normal was the boiling hot fuel that was bled out of the fuel rail. (vapor lock) That immediately corrected the no start condition.

Any idea what caused the fuel to heat up? Bad wiring?

I'll take your advice and unplug it and see what happens, and then go from there.

Any update?

 

[tgui]

Andy, you have several catalytic converters with sensors to monitor their performance. Hollowing them out will trigger check engine lights. There are fixes for this however.

Yes. This. As someone temporarily living without cats the smell at stoplights can get pretty bad. Its not worth it.