2007 GMC Denali stalls after towing

[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.