I installed a Dawes boost controller a couple of weeks ago. Before I installed it, I was getting around 8 psi max according to my gauge.

After the install and an adjustment, it was around 14.5 psi max, which was too much. I was running out of time so I only had a chance to make one ore change to it, in which I erred too far in the other direction - I ended up with 7.5 psi max.

Oddly enough, that's less than I was getting originally, which shouldn't happen (the wastegate is still hooked up) but I didn't make note of it at the time.

Today I had some time to play with the boost controller and no matter what I do, I get 7.5 psi max... always. Even if I adjust the controller far beyond where I was getting 14.5 psi before, it stays at 7.5. Hell, I removed the controller completely and left the wastegate hose unconnected to anything (should vent right out, no pressure at all I'd imagine) and I was still getting the same boost pressure!

Am I crazy? Does anyone have any idea what might be happening?

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

Hello 81Wagon
Sounds like a mechanical jammed waste gate or your gauge is broken.
Just for grins; check your vacuum supply, you may have accidentally cracked a hose and be fighting leak/loss.
This is the type of issue that can drive you nuts.

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Can't be. That wouldn't stop the boost controller (which comes before the wastegate) from upping the boost past 7.5 psi max. Nor does it explain the fact that somehow I get boost with the wastegate hose completely disconnected.

It's a brand new Isspro gauge that was working fine two weeks ago; I suppose it might have broken but that still wouldn't explain how I seem to get boost with the wastegate hose disconnected.

This is interesting. How does the vacuum interact with the boost pressure? Tomorrow I'm going to borrow a mityvac and check a few things (the accuracy of my boost gauge, for one). What should I look for? I've never messed with the vacuum system before.

__________________
'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)

Might try to isolate the problem. Take out the boost controller and plug the manifold port. If it can reach 15 psi easily, then the boost controller and/or wategate is the problem. Not to suggest you run it like that, just for testing.

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Shane83SD

check the wastegate linkage for movement. It may be stuck, or the link may be loose. I've seen the Garret turbo with no linkage at all -- fell off somewhere -- and hence little or no boost.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!