Just today I fired up the Cummins for the 1st time in a few months. It had a broken motor mount, and a torn intercooler boot, the tags expired while it sat and I had been driving other vehicles. I installed a new motor mount, and a new silicone boot, and a new air filter while I was at it. I have to go through emissions so I also temporarily tightened the star wheel as tight as I could get it with a screw driver (it was as loose as it would go before ).

I took it for a test drive, and it was noticeably slower off the line with the AFC back in control again, which I expected. What I didn't expect, however, was the boost would stop climbing around 10psi, where it felt like I hit a wall and the exhaust just belched black smoke after that.

Like I said, the air filter is new, so there shouldn't be any intake blockage. I didn't change anything on it while it was sitting except for the star wheel adjustment in prep for emissions testing. Is this a symptom of getting the star wheel too tight?

 

i say you have a leaky IC boot yet.

 

Or your wastegate is stuck partially open.

 

I checked all the IC boots pretty thoroughly, but I might build a rig that attaches to the inlet of the turbo and has a valve stem on it for pressure testing. I'll check the wastegate, I think I'll have another break in the rain this afternoon.

 

I think your star wheel is too tight. I was doing some messing around with mine a couple years back. and if I tightened mine all the way like you said you did then I could only get about 12 psi and it would never get off of the afc foot. It was obviosly a total dog like that. mabey try and back your starwheel off I bet it will help.

 

Well I passed emissions, and loosened the star wheel back up. Its not as painful to drive, but still don't get the increased boost (and it REALLY smokes black at WOT now lol). I have a couple other things to check.

 

When I first got my truck in '05 I read this forum everyday to learn all I could about it as this is my first diesel.In my learning process, I did some experimenting with the star wheel settings.At first I made small changes and didn't notice any difference, then I ran it all the way back.The next day I pulled my travel trailer to my son's for storage.I couldn't get over 45 MPH on the highway.The only thing I had changed was the star wheel adjustment so I pulled off the highway and ran the adjustment about 2/3rds open and the truck ran fine.Somehow running that star wheel all the way back did not let the truck get fuel.I'm sure some of the regular guys on here can tell you why.I did a search on the 12V forum and could'nt find any info .

 

When you move the starwheel, you are adjusting the preload on the AFC. Obviously, the more preload you have, the more boost you need before it even begins to move forward. If you have it really tight, and the housing all the way back, you won't get enough fuel to create the boost needed to move the AFC. At that point, you would have virtually no smoke, and would be a dog to drive.

Since the OP's truck is smoking something awful, he is lacking air for the fuel. Either boost leaks, leaking wastegate or a terribly plugged filter is my guess.

 

This is weird. I hadn't been watching the boost gauge when I made my last post, rather the amount of black smoke. The boost does make 20+psi, and the black smoke cleared up over time. Don't know why, but it seems to be back to normal.