2007 Yukon 6.2 stalls/won’t start when hot

[Campie]

Hi all, new member here. We have a new-to-us 2007 Yukon Denali 6.2 with ~158k miles. Primary use is to pull a small horse trailer and a 17’ travel trailer. Max load is ~5500 but the travel trailer is pretty tall and 8’ wide. No problems with power or stability towing unless it’s hot weather - then we’ve had the “stalled and won’t start” issue once we get off the highway. We’re old enough to remember vapor lock and that’s exactly what it seems like. Got a new fuel pump and filter already (with the milage it was time) and sprayed the MAF sensor (should there be a screen on that MAF at the intake side? Ours doesn’t have a screen?) so we’d like to try insulating the fuel rail next. We’ve had a time or two of longer crank time when the engine was cold but that was before the fuel pump. Is there a video of how to insulate the fuel rail? Also thinking of replacing the cam and crank sensors but thought we’d try the cheap, easy stuff first. We’ve both worked on cars 87 years ago but nothing recently, never done major repairs and we don’t have a lift but we’d like to learn more. So glad to have found such a great group of resources!

 

[Dustin Jackson]

@Campie I can't think of anything that would cause it to not start once it's hot but when I experienced cranking without ignition was after a rebuild, I didn't have the negative battery cable tightened all the way down to the front of the passenger side head. After I tightened that it fired right up.

 

[Campie]

Lol, it does start eventually but it’s like vapor lock. There’s a whole bunch of information on this forum about this issue so it’s for sure not uncommon. What I’m looking for is a video or help understanding exactly how to wrap/ insulate the fuel rail.

 

[rdezs]

Sounds to me like your vapor Purge solenoid. It literally takes just a couple minutes to change it. If it's stuck open, it's getting flooded with fuel vapors from the carbon canister. Pretty common issue.

Below is a picture of it and the part number. You'll see it on the driver side of your intake manifold alongside the fuel rail.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I also have an 07 Yukon (XL) Denali with about the same mileage, but I have never experienced this issue.

Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.

Are you getting a spark to the plugs when you try to start it hot? It would be interesting to see what the fuel pressure is when you try to start it hot. It would also be interesting to see if the evap/emissions system is working properly when hot.

Other members of this Forum much more knowledgeable than me in this area will chime in.

 

[Campie]

Sounds to me like your vapor Purge solenoid. It literally takes just a couple minutes to change it. If it's stuck open, it's getting flooded with fuel vapors from the carbon canister. Pretty common issue.

Below is a picture of it and the part number. You'll see it on the driver side of your intake manifold alongside the fuel rail.

View attachment 459865

Oh, that looks easy enough for me to try and it’s cheap! Thanks!

Thoughts on the MAF screen question? There is no screen. The tiny wires inside look fine. I’d replace it but it’s $600. I did spray it with the correct cleaner and the mileage when up about 2 MPG - so nice!

 

[Doubeleive]

Oh, that looks easy enough for me to try and it’s cheap! Thanks!

Thoughts on the MAF screen question? There is no screen. The tiny wires inside look fine. I’d replace it but it’s $600. I did spray it with the correct cleaner and the mileage when up about 2 MPG - so nice!

it's not $600, more like $75 or so (guessing your shopping gucci store?) but, also unlikely to be the issue

 

[Campie]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I also have an 07 Yukon (XL) Denali with about the same mileage, but I have never experienced this issue.

Do you have, or have access to, a quality bi-directional scanner? If not, I recommend that you get yourself a quality bi-directional scanner to add to your tool box. Then, you will be able to read ALL trouble codes, along with a brief explanation/pointer to the source of your issue. You can test many of the truck's electronic functions with the scanner, in order to determine the source of an issue. You will also be able to reset/delete trouble codes, after taking corrective action. You will literally save thousands of dollars in diagnostic and repair costs over the life of your truck, and you will most likely recoup the cost of the scanner within 1 year.

Are you getting a spark to the plugs when you try to start it hot? It would be interesting to see what the fuel pressure is when you try to start it hot. It would also be interesting to see if the evap/emissions system is working properly when hot.

Other members of this Forum much more knowledgeable than me in this area will chime in.

Love this forum and yes, so many helpful folks! I’m way in over my head most of the time though…

I did get a scanner but haven’t found the time to learn much about it.

Really seems like it’s just not getting fuel - like a vapor lock. Not sure I could figure out how to connect up a separate fuel gauge to the rail. I think it’s a Shrader valve so I just need the correct gauge.

It’s only done this twice and both times were pulling the camper on a hot day on the highway, getting off for gas. It’s stutters at the top of the ramp but stays running. But then it will stall shortly after as we pull into the gas station. Both times we still had 1/4 tank so it’s not running out of gas but that’s what it seems like. And both times, after 10 or 15 minutes it started again.

 

[Campie]

it's not $600, more like $75 or so (guessing your shopping gucci store?) but, also unlikely to be the issue

I checked with GM and my local shop and both quoted ~$600. Do you have a source that’s cheaper?

 

[Joseph Garcia]

I checked with GM and my local shop and both quoted ~$600. Do you have a source that’s cheaper?

RockAuto.com and GMPartsDirect.com

 

[rdezs]

If somebody quoted you $600 for the mass airflow sensor... Run away.... Fast.

Start looking on rockauto.com. They list about 10 or 15 choices, usually they have a GM AC Delco listed but not in this case. I would go for one that includes the whole housing. (Walker brand maybe) Prices are reasonable, even on OEM stuff.

 

[Doubeleive]

just get the delphi, same thing gm uses anyway in many cases. sometimes you get a gm box and delphi part or a ac delco box and delphi part, so on so forth.....in these case you are just paying extra for the"box"

 

[rdezs]

I noticed his post described missing the screen..... So I'm assuming he needs a new housing, didn't see a Delphi unit with the complete housing.

 

[Campie]

Sounds to me like your vapor Purge solenoid. It literally takes just a couple minutes to change it. If it's stuck open, it's getting flooded with fuel vapors from the carbon canister. Pretty common issue.

Below is a picture of it and the part number. You'll see it on the driver side of your intake manifold alongside the fuel rail.

View attachment 459865

Wow, thanks so much for this! Do you have a part number for the MAF also?

 

[Campie]

Right and the MAF that’s in ours doesn’t look like you can replace just the insert but it is ACDelco brand.

 

[rdezs]

The part numbers are above in the screenshots from RockAuto. Or you can just go to RockAuto. It's actually somewhat important that you have the housing with the screen intact in it. Officially it acts as a diffuser, smoothing out the airflow so that your mass airflow sensor can give an accurate reading.

Delphi is a better quality part compared to what else they offer.... But you really do need to find a housing with the screen. Salvage yard maybe?

 

[rdezs]

Hell, you could probably get a used mass air flow sensor with the housing off eBay..... And then install the Delphi sensor into that housing.

 

[Campie]

Sorry, I’m new to navigating the forum so I missed them. I’ll get an air filter also although ours doesn’t look bad. Maybe a ACDelco or is there another brand you suggest?

 

[Campie]

I did order an MAF off Amazon but it came with a damaged screen - go figure! Also it doesn’t look like the insert will come out of the one in the car now. I’ll order the Walker and see if I can switch the insert.

 

[rdezs]

AC Delco or wix for the air filters