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Tow Rig Issue - Any Ideas?


vaporbluebu

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2008 GMC Yukon XL Denali

This past weekend I pulled the boat 380 miles with no issues. The next day we drove 15 miles to the ramp and when I pulled into the parking lot the engine shut off. Tried cranking it a few times and nothing.I was thinking maybe the fuel pump had died. A guy came over and after some discussion I pumped the gas while cranking and eventually got it started, but when it did start it was like starting my driving lawn mower that has sat all winter...Very sluggish and boggy and had to keep pumping the gas to keep it alive. Once it finally caught, it came to life and seemed normal. Revved the engine a few times and all was well. Launched the boat, retrieved, drove back to hotel and all good. Next day drove back to the lake just fine, but on the drive home at a stop light I could tell it was about to die so I pushed the brake and gas at the same time and kept it going. Got back to hotel, packed up for an hour and left for the drive home. Driving through town it was fine and did about 60 miles on the freeway before stopping for dinner. As soon as I pulled off of freeway it died. Struggled to get it started again but finally did and if I kept it the rpms at 1500 or more it was ok. Ate dinner, fired right up, and got back on freeway and drove 300 miles no problem. But again when I got off for last fuel stop it wanted to shut down, but I was ready for it and would shift into neutral and rev to keep the rpms up. I did add some injector cleaner at the last fill up but only put about 30 miles on it since then. My wife has driven it a little today around town with no issues?

Any ideas? Thanks

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54 minutes ago, vaporbluebu said:

2008 GMC Yukon XL Denali

This past weekend I pulled the boat 380 miles with no issues. The next day we drove 15 miles to the ramp and when I pulled into the parking lot the engine shut off. Tried cranking it a few times and nothing.I was thinking maybe the fuel pump had died. A guy came over and after some discussion I pumped the gas while cranking and eventually got it started, but when it did start it was like starting my driving lawn mower that has sat all winter...Very sluggish and boggy and had to keep pumping the gas to keep it alive. Once it finally caught, it came to life and seemed normal. Revved the engine a few times and all was well. Launched the boat, retrieved, drove back to hotel and all good. Next day drove back to the lake just fine, but on the drive home at a stop light I could tell it was about to die so I pushed the brake and gas at the same time and kept it going. Got back to hotel, packed up for an hour and left for the drive home. Driving through town it was fine and did about 60 miles on the freeway before stopping for dinner. As soon as I pulled off of freeway it died. Struggled to get it started again but finally did and if I kept it the rpms at 1500 or more it was ok. Ate dinner, fired right up, and got back on freeway and drove 300 miles no problem. But again when I got off for last fuel stop it wanted to shut down, but I was ready for it and would shift into neutral and rev to keep the rpms up. I did add some injector cleaner at the last fill up but only put about 30 miles on it since then. My wife has driven it a little today around town with no issues?

Any ideas? Thanks

Sounds like bad gas or a clogged fuel filter.  I wonder if along your trip you picked up some bad gas at a station (either crud or water in the tank.)  The last time it happened it sounds like it was before a fuel stop.. were you low on gas each time it occured?  

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1 hour ago, gregtay said:

Sounds like bad gas or a clogged fuel filter.  I wonder if along your trip you picked up some bad gas at a station (either crud or water in the tank.)  The last time it happened it sounds like it was before a fuel stop.. were you low on gas each time it occured?  

No, about a half tank each time. I let it get low the last time so I could add injector cleaner. Will look into the fuel filter.

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1 hour ago, RyanB said:

Sounds like it could be fuel pump to me. 

The only time I’ve had a fuel pump go out the pump quit completely and the car died while going 55 mph down the highway. Can a pump die a slow death where it isn’t able to pump at low fuel flows, but seems to work at high loads?

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My guess is the fuel pressure regulator, or the vacuum line that goes to it (because it seems to vary with manifold pressure).

You could attach a Harbor Freight fuel pressure gauge to see what the pressure is doing.  That would check the fuel pump, regulator and filters.

Edited by MadMan
  • Like 3
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3 hours ago, vaporbluebu said:

The only time I’ve had a fuel pump go out the pump quit completely and the car died while going 55 mph down the highway. Can a pump die a slow death where it isn’t able to pump at low fuel flows, but seems to work at high loads?

Mine did. But it was in my Cummins. 

  • Like 1
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4 hours ago, vaporbluebu said:

The only time I’ve had a fuel pump go out the pump quit completely and the car died while going 55 mph down the highway. Can a pump die a slow death where it isn’t able to pump at low fuel flows, but seems to work at high loads?

My Malibu's pump did that!  Before it died totally.

Edited by Eagleboy99
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Before doing ANYTHING else, get a real code reader (like the Blue Driver unit) to scan everything.  Could be what are referred to as shadow codes on one or more systems (codes that pop up but do not throw a light).  Even if it turns up nothing, you should still have one.

GMT-900's don't have fuel filters.  Possible fuel pump death but I wouldn't expect you to make it that far on it.  Highly doubt it is the air filter.  Possible sensor issue, IAC valve or other problem.  Scan first then troubleshoot.

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5 hours ago, Cole2001 said:

You can stop at any auto zone and they will scan it for free and give you a print out diagnostics. 

They use a basic $20 OBD scanner that barely shows anything.  

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5 hours ago, Nitrousbird said:

They use a basic $20 OBD scanner that barely shows anything.  

Yeah, these newer vehicles have so many "hidden" codes that you often need the factory scanner to get the right (or any) code.  Those 5 buck ones off eBay are fun, but no probative value in diagnostics.

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10 hours ago, Eagleboy99 said:

Yeah, these newer vehicles have so many "hidden" codes that you often need the factory scanner to get the right (or any) code.  Those 5 buck ones off eBay are fun, but no probative value in diagnostics.

No need for a factory code reader.  Blue Driver does it for $99

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15 hours ago, Nitrousbird said:

They use a basic $20 OBD scanner that barely shows anything.  

The one that the local O'Reilly has is full featured and shows all the mfg specific codes. 

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23 minutes ago, Nitrousbird said:

No need for a factory code reader.  Blue Driver does it for $99

I see that BD only offers enhanced diagnostics (ie. airbag  or ABS) from  a few brands.  neat, nonetheless.

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1 hour ago, Eagleboy99 said:

I see that BD only offers enhanced diagnostics (ie. airbag  or ABS) from  a few brands.  neat, nonetheless.

This is a tow rig thread.  It does enhanced diagnostics for GM, Ford, Chrysler (including Ram, Jeep, etc), Toyota and NIssan.  That covers pretty much every full size truck out there.

Now we are talking towing SUV's beyond those brands.  BMW and VW/Audi covered (though there are some basically free options if you have a cable for BMW).  I guess if you tow with a full size Benz you don't get those features.  Due to the parts share with the Q7, the Porsche Cayenne may/may not be included.  Let's be fair, 95% of tow rigs on this forum are covered.  That's a sold percentage for a $99 diagnostic tool.  It paid for itself a couple times over the first time I used it.

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Much of what has been mentioned here as possible issues, should have thrown a code and lit up the check engine light... low fuel pressure, clogged filter, fuel pump etc...

My guess is something is up with the ECM itself and not throwing codes...

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