My CRD has been throwing overboost codes for a week now. If I rev it over about 2000rpm it will throw a P0234 and go into limp mode. So I bypassed the boost solenoid, etc, with no luck. Initially it seemed like the actuator was moving normally, but now it barely moves when I remove and replace the vacuum line. So I figured, OK, I'll work the actuator a bit and see if I can free it up (since I can't give it a hard-run to try to burn it out). I worked my hand back in there to grab the bottom of the actuator lever arm and pulled for all I was worth and couldn't hardly budge the arm. So then I grabbed the Mityvac and applied vacuum to the actuator. It doesn't move at all until about 15PSI, and then only 1/4" to 5/16" up to about 20PSI. I did this a bunch of times and it didn't make any difference. So Finally, I reach back to grab the actuator arm again and as my hand runs past the lock nut on the arm, it spins freely! I can run it all the way to the top and back with no resistance. So now I have no idea how much the actuator arm has moved during all of this. I pulled the front (intake) half of the turbo off in one piece to work on it on the bench. The vanes in the exhaust half move freely and the actuator in the intake half seems like it can move fine...it is just the downward pressure from the actuator preventing it from moving. I have not unbolted the actuator puck from the turbo body to try to move JUST the actuator arm. I don't know what the vacuum pressure is supposed to be for a CRD, but it doesn't seem like it is anywhere near 20PSI...so at what pressure should I expect to see the ideal 1/2" actuator movement?

Should I be able to move the actuator by hand with the vacuum lines removed and the puck connected?
At what pressure should the actuator be fully engaged?
How do I determine where the adjuster needs to be set on this thing?!?!

HAAAALP!!!

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2006 Limited CRD: Frankenlift II, Fumoto Drain Plug, DIY Stage 1 Tune, In-Tank Lift Pump

Inside the vacuum actuator is a diaphragm and a spring. I don’t know how heavy the spring is and I don’t know how much vacuum is needed to move it.
However, I do know that high vacuum = high boost.
So if overboost is your problem, then you have enough vacuum.

With the actuator completely removed from the turbo, you should be able to move the little lever and move the vanes by hand.
Typically this is what gets jammed up and causes boost problems.

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U.S. Army Retired

The spring is quite heavy. I just swapped mine from my stock turbo to the new turbo from diesel guy and I couldnt really move it much. Imagine though that the diaphragm is like 7 sqin, is it’s a 3 in diameter so 20 psi is a lot of force.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs

Not sure how easy you can work on it, but if possible, put max vacuum on the actuator and adjust the knurled nut on the black part on the actuator rod. It should thread UP the rod until the arm hits the stop screw. Then bleed off the vacuum and it should drop down to where it is currently sitting. If it doesnt then the vane system is plugged with carbon. This will get you back to normal.

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05 Liberty Limited CRD, converted to KPA 2863 ball bearing and billet turbo, 50hp injectorsl, complete egr delete, cooling fan delete, weeks intake kit, cummins in tank lift pump, ARP studs, 3" turbo back exhaust, samcos, etecno plugs, GDE trans tune, custom GDE engine tune.

Corey (Cory?) from IDParts was kind enough to answer my question...4 years ago.

https://www.youtube.com/watch?v=gYkNMOzsk14

I know that is a different turbo from a VW...and so things may not be exactly the same. I set mine up using his numbers (inHg, not PSI!) and so far so good. I'll find out tomorrow if everything is as it should be when I hit the highway on the way to work. The short run I took around the roads where I live produced no codes, where it did before taking everything apart. It did feel a little bit sluggish, but that might be relative to the overboost I have been driving around on for who knows how long. On a side note, does anyone have an old OEM turbo they want to get rid of, working or not?

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2006 Limited CRD: Frankenlift II, Fumoto Drain Plug, DIY Stage 1 Tune, In-Tank Lift Pump