2004 Yukon XL (Non Flex) cranks but doesn't start.

[2004YukonXL_SLT]

How long has it been sitting? Could just be bad gas or someone helped make the gas bad by adding water, cheerios, Cheetos, Pepsi, Sugar or a host of other things that aint suppose to be in the tank.

It has been sitting for about 2 years, I made the dumb mistake of running the truck on old fuel and I may have gummed up the injectors. I tried starting it with some engine starter with no success.

 

[MassHoe04]

If you got it to sputter or make any kind of noise resembling combustion...
Try tossing in some Heet or Dry-gas. If parked that long, there might have been a lot of water condensation in the tank.
It could be injecting enough water to cancel out the starting fluid you are spraying in to allow it to fire and run.

 

[2004YukonXL_SLT]

I'll give the alternator a shot, the battery is brand new and fully charged (got it replaced under oreilly auto warranty). I have a spare alternator lying around that was tested good.

Thank you for the help!

Having seen something similar, I suggest you check the alternator output, at load if possible. Your alternator may be dying. I'd get the battery tested as well. Finally, might want to check if tensioners and pulleys are working correctly. But this totally feels like a dying alternator to me.

Good luck -- stuff like this is the unfun part of any automotive work.

OK! Good news! I got the Yukon to fire up and drive, it doesn't seem to bog down or die anymore, but it is hesitant under acceleration, I should test to see what my fuel pressure is running while the engine is idling right?

But I ran into another issue, I took my known good alternator, and now the battery isn't charging anymore... What could cause an issue like that?

 

[2004YukonXL_SLT]

If you got it to sputter or make any kind of noise resembling combustion...
Try tossing in some Heet or Dry-gas. If parked that long, there might have been a lot of water condensation in the tank.
It could be injecting enough water to cancel out the starting fluid you are spraying in to allow it to fire and run.

Ok so I got it running and put some new fuel and a fuel additive to get everything to play nice.

I still have the issue where the battery isn't being charged using an alternator that is confirmed working, but after sputtering around for about 10 minutes I got it to throw a crankshaft position sensor code. I'm going to let the engine cool down for a bit and swap it with a new part that I have from another project to see if that helps the sputtering and VERY HESITANT acceleration.

Thank you for your help. I'll keep the thread updated while I continue to work on this for documentation purposes.

 

[MassHoe04]

Changing the crank position sensor will require a "re-learn" procedure to be done for the new sensor.
Do you have a Tech 2 scan tool to do that re-learn?

I am not sure if other non-Tech 2 bi-directional scan tools are capable of doing the sensor re-learn or not...

Possibly unrelated side note:
If the battery was disconnected for a while, the engine control module clears out some of the data on air/fuel adjustments it made. The engine can run rough until sensors provide enough new data to make new adjustments to make it run as it should.
Might not have anything to do with the crank position sensor code, but the computer can make the engine rough for a bit while things settle in again after full power drain.

 

[2004YukonXL_SLT]

Changing the crank position sensor will require a "re-learn" procedure to be done for the new sensor.
Do you have a Tech 2 scan tool to do that re-learn?

I am not sure if other non-Tech 2 bi-directional scan tools are capable of doing the sensor re-learn or not...

Possibly unrelated side note:
If the battery was disconnected for a while, the engine control module clears out some of the data on air/fuel adjustments it made. The engine can run rough until sensors provide enough new data to make new adjustments to make it run as it should.
Might not have anything to do with the crank position sensor code, but the computer can make the engine rough for a bit while things settle in again after full power drain.

I don't think I do... I have the Foxwell NT301 tool.
That would explain why nothing changed when I ran around the block again.
Is that something a shop would need to do for me?

 

[MassHoe04]

If this truck is a keeper (for at least a while)... There is bound to be more work to be done, I am sure.
$239 (on sale from $300) will get you a Tech 2 clone from Chinacardiags.com.

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If you are in a hurry and need for daily driver, then yeah... Shop will need to re-learn the sensor for you.

If you can wait for the shipping, having a Tech 2 of your own will save the shop labor for the sensor re-learn. Avoiding that trip alone will save half of the cost (or more) of the Tech 2 right away.

Strongly encouraged to get one and have it, if this truck is going to be around for a while. So much you can do with the tool, you could save thousands in shop fees.

 

[rockola1971]

When gas gets old it loses octane. You need atleast a 87 octane rating for your PCM and Engine to run correctly without a bunch of spark knock. You need to add a bottle of octane booster to the tank of gas you have in there and run it down to almost empty and then add in 8 gals of 87 octane and 2 gals of E85. (E85 has an octane rating over 100).

 

[Fless]

Put the old crank sensor back in. The more variables you introduce, the more complicated the diag becomes.

Will it fire up on ether?

Back to the basics: verify spark, fuel, air (and compression, if you get to that point).

 

[MassHoe04]

Put the old crank sensor back in. The more variables you introduce, the more complicated the diag becomes.

Will it fire up on ether?

Back to the basics: verify spark, fuel, air (and compression, if you get to that point).

Good point @Fless At this point, I don't think we have been able to determine if the crank position sensor was bad to begin with... I almost mentioned going back to the original sensor for now, at least until it can be determined the sensor is junk. For some reason, I didn't.

Note for the OP: A good bi-directional scan tool will allow you to dive in to see what the sensor is doing. For less than $300, a Tech 2 will do that for you PLUS the ability to do things like crank position sensor re-learn, a million different module diagnostics and various other sensor reset/test/programming functions. Like I said earlier... If you plan on keeping this truck (or a GM of similar vintage), having a Tech 2 can save huge amounts of diagnostic time and money doing things DIY instead of paying a shop. It will be way more advanced than your immediate needs, but for the money, you will be ready for the more advanced functions you might need later on.