Jfitz

Car repair question - '07 GMC Yukon

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Hi all - are there any auto mechanics or general motor-heads here that can offer some advice?

I have a 2007 Yukon Denali 6.2L.  A few times now it has died on me under the same circumstances - driving at highway speed, then slowing at off-ramp to a red light where I stop - and the engine stalls.  Car will crank, seem like it 'wants' to start, but no joy.  No trouble codes logged.  Plenty of fuel.  In all 3 instances, I had to have it towed (twice to my local mechanic, once to a dealer).  All 3 times, it was towed and left in the lot - and then, by the time they got to it, it started right up and they drive it into the service bay.  All systems check out fine.  No trouble codes. The last time, they drove it around multiple times over several days while connected to their diagnostic computer and all systems looked good.  Needless to say this is frustrating.

From my searches on the interweb, I'm suspecting the oil pressure sensor is bad, and that the fuel pump relay is 'iffy' - it works 'most' of the time, so that the relay powers the fuel pump until it faults (maybe when it gets hot) and then nothing powers the fuel pump.

Question - from info I can find, it looks like the oil pressure switch also serves as a power source for the fuel pump, so that either the relay OR the oil pressure sensor can power the fuel pump.  Can anyone confirm this?  If it is running and I pull the fuel pump relay from the control block, the car stalls.  Very similar to how it died on me.   Any info or advice would be appreciated

 

 

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I know little about modern cars. But given the high cost of mechanics I would price those parts and replace them myself. 

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37 minutes ago, Tom King said:

I haven't kept up with newer engines.   Is this a diesel, or a gas burner?

http://www.thedieselpageforums.com/tdpforum/showthread.php?t=33432

Gasoline.

45 minutes ago, wdwerker said:

I would price those parts and replace them myself.

I usually agree. I'll replace the fuse relay myself - 10 second job.  I bought the oil pressure sensor and....well, let's just say it's in about as tough a place as can be.  I'll do a lot,but this one concerns me. Some people have done it without removing a lot of parts, but the 'preferred' method is to remove the entire intake manifold (and all the wires and stuff along with it), since the sensor is between the intake manifold and the firewall.  

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It seems really weird to me that it's stalling out but it's not showing up on a scan. That's got me thinking it's fuel pump that for what ever reason when the voltage drops after a while on the highway it just stalls out. The trouble is fuel pumps aren't an easy fix. That oil sensor sounds easier than dropping the tank and having to deal with all the gas.

I have no idea for ya though.

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A buddy of mine had a fuel pump die in his  Ford truck. The dealer told him it's mounted in the gas tank so that the fuel acts as a heat sink. Recommended that he try to keep the tank at least 1/4 full to extend the life of the new pump. A month later the new pump died and they tried to wiggle out of replacing it. 

Good luck with your repairs !

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I'm hoping it's not the fuel pump - they're int he tank. What a pain.

Alternator - hmm.  The battery had tons of juice, but I suppose it could be electrical...

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A Google search for "GM 2007 6.2L stalls" found plenty of discussions about similar, if not the same, issues.

such as:    http://www.gmtruckclub.com/forum/threads/07-yukon-denali-stalls-and-wont-restart.1084178/

How old is the battery?   I have heard of strange things happening to computers when batteries get weak.

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9 hours ago, Tom King said:

A Google search for "GM 2007 6.2L stalls" found plenty of discussions about similar, if not the same, issues.

Thanks Tom. I found that article in my searches - and now, between that and other comments about alternator and battery, I think I'll go back to basics the next time if/when it happens:  Spark, fuel, compression.  Maybe I'll just use it for my around-town vehicle for a while.

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A growing trend for some of this age of vehicle is the capacitive discharge. You don’t do this at home if any of your modules need to be reflashed, but basically this performs a hard reset on every module. I am only recommending research. Some computers that are constantly on just need to reload to clear some bugs. 

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My wifes 2005 Ford Taurus does this as well if you find the culprit please let us know.   When this happens on her vehicle (probably once every 2 months) we let it sit (1 to 10 minutes) and it runs fine until the next 2 months or so.  Goodluck

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