I just got a '04 GMC Duramax with 127K miles and it puffs out some white smoke. I took it to a dealership and he said the injectors were ok and that it had some bad fuel in it. I put two bottles of Stanadyne it and thought that might clear it up, but it didn't. I've been running red fuel in it hoping that would help but haven't seen a difference. I need suggestions on what's wrong and/or how to fix it.

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the truck was smoking way before I ran the red fuel in it

 

Somebody correct me if I'm wrong but I'm thinkin it may be a head gasket?

 

if it is a headgasket, you can check for water in the oil or take the radiator cap off and start it. Check for bubbles in the coolant (compressed air from the cylinders causing bubbles). Does not always work but cheap to check.

 

/me moved thread

 

Pull your dipstick and see if it smells like diesel fuel. White smoke typically is either a head gasket or an injector sticking open slightly. What tests did the dealer run?

 

Bump

 

Depending on the amount of white smoke (even in a DMAX) the CP3 (injection pump) might be starved of fuel some how.

Red fuel will not cause this - a plugged fuel filter might but you would have hard starts as well.

Assuming your injectors are all good and you don't have any leaks present - I would first start with the fuel filter. Next, I'd move to testing the pressure at the pump. Since you may or may not (depending on 2004 build date) have a lift pump on that truck you should check to see if that is working correctly as well. If no pump is present I'm not sure you can check the pressure on the test port but you can give it a try.

You will want at least 5psi if memory serves.

If this is not the case and you have a lift pump, you may want to see if that is working at all. If it isn't get a replacement FASS (or equal) and then test the pressures. Regardless, you may need to convince the dealer to take a long hard look at the CP3 and see if it is damaged or failing in some way. See if you can get the codes scanned and see if they will give them to you so you can report back.

As you can see I'm full of ideas but I don't have lots of experience with the DMAX - just enough to get them running...

 

04' duramax as in Lb7 right?

the injectors fail in two ways, they either pour fuel in the crank case or it just smokes out the tail pipe with gray white smoke at idle.

if you can get some one with a predator tuner, or PPE, or EFI live tuner to check balance rates. if anything is +/-4 your injectors might be going south

 

Have you solved this yet?

 

/me Closing er' down assuming issue is fixed ... Moving On , Thread starter can reopen this thread if they wish