I searched a bit and although I KNOW this has been discussed I must ask agaion.. sorry.

My 1983 300SD with 300K miles is only showing 4lbs or so boost on my aftermarket Sunpro boost gauge.

This gauge used to read 9.5 under load.

I cleaned the hose from manifold to overboost protection to ALDA.
My line for boost gauge is after the overboost protection and before ALDA.

When the gauge stopped climbing a while back I cleaned that line again
and cleaned out the overboost valve.

Today I inspected the line from manifold to wastegte, thinking it was leaking.
While I had the tube from air cleaner to turbo off I stuck my finger in there to
see how well the blade spun, it was okay, but not spectacular...
I could give it a spin, but it did not free wheel like say - a bicycle tire.
It spun a little then stopped.

My impression is that turbos never go out. Maybe I am wrong.

I keep thinking the banjo bolt and line are clogged. But they seem really clean.

And last - the car runs acceptably good. It still is way more powerful
than the 1980 non turbo.

Before I replace the turbo I am looking for other low boost options.
Can the wastegate be bad ??

Any other things to check .
Thanks.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

The wastegate spring gets weak, you could install a boost controller.

The overboost protection will prevent overpressure from getting to the ALDA and gauge. Are you sure it is working?

I think Id rather have the gauge before the overboost protection, so I know the pressure the turbo is truly putting out. MB sets the turbo pressure very conservatively for life, and Id want to know and verify that it isnt running some funny way where it is putting out too much presure, but I cannot see it because Im after the protection.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (116k)
1991 350SD (206k)
1991 300D (228k)
2008 ML320 CDI (199k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (267k)

Past Diesels:
1983 300D (228K), 1985 300D (233K), 1993 300D 2.5T (338k), 1993 300SD (291k)

THANK YOU. I was geting worried when no one chimed in.

Good point. Tomorrow I will move the guage line to pre-overboost valve.

2nd... I happen to have an adjustable boost controller that I have not installed.

I will install it on the wastegate hose.

Might do an experiment where I plug the line to wastegate to see
what changes.

I understand the dynamics and seem to think the max of 13 lbs pressure is all a stock system should be allowed to have.
But just getting back 9.5 to 10 would be nice.

From the way it drives I keep thinking that I am getting the boost, just not
the fuel from the ALDA .

Thanks. I'll report back.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

Installing a boost controller on my 84 300SD made ALL the difference in the world. Great little device. I let mine top out at 11.

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

No need to guess how much you are boosting. Simply T a gauge into the line, run it back to the cab & go for a drive.

I made a boost boot to check for a boost leak on the diesel Ram which has more plumbing (intercooler etc) than the SD. Basically, you attach the boot to the front of the turbo & blow regulated air into the system & listen/feel/spray soapy water to check for leaks. I wouldn't even consider the turbo as bad if there is no play in the shaft and the vanes don't hit the housing.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Okay - boost controller is going to be the answer, wastegate must be the problem.

This morning I first took over-boost-protection out of the equation.
Line from banjo on manifold straight to T for ALDA and boost gauge.
Gained 2 to 3 pounds boost. Hitting 5, maybe 6. Still not enough.
But removing the over boost protection helped.

Next I went to install boost controller - fittings are not correct size.
Need to buy new barbed fittings. So... I plugged manifold
line completely - for testing purposes only.

Test drive produced 10 solid pounds of boost. Very nice.

I will get correct fittings and tune the release of boost controller.

The few dollars that boost gauge cost me have been well worth it.
Knowing your boost amount in numbers is great.

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
02 Z71 Suburban 117,000
15 Toyota Prius 2600 miles
00 Harley Sportster 24k
09 Yamaha R6
03 Ninja 250

Where did you get the boost controler and how much did it cost?

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Gary
OBK #37

I got mine off of ebay a couple of years ago.
I think it was around 20.00.
Be sure to install a boost gauge to monitor it or you could
damage the engine by having the boost too high.

Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

It's my understanding that most of these engines loose boost over the years but you can readjust the waste gate, I did on my car, to bring the boost back up to spec.
The specifications for this are .7 to .8 bar or 10.15266 to 11.60304 psi.
I have the kkk turbo on my car and it wasn't hard to adjust BUT you do burn yourself if your not careful. I found this out by not being careful

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1983 300SD
200000miles

Is this were you made your adjustmant (red arrow)?

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84 300D, 82 Volvo 244Gl Diesel

I have a boost guage installed and have a max of 9 psi of boost, I would like to up it to 11 after I check chain stretch and IP timing. I looked on Ebay but not knowing what it does and how it does its thing I do not know what to get. Where does yours connect, is it mechanical or electricly controlled, and could you look on Ebay and see if your style is still on there? Thank you.

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Gary
OBK #37

Here you go

Turbocharger Wastegate Adjustment:

Amazing what's in the archives.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

Mine is a little different, see picture, but same idea. There is a lock nut around the adj. screw, red arrow. Loosen the nut then use an allen wrench to turn the screw then take it on a test ride. What you are adjusting is the spring tension inside the waste gate. You need a gauge connected but I just put one in line and ran the tube through the passanger side window so I could see what I had. I had to adjust it two or three times to get it where I wanted then just tightened the lock nut. Some day I want to install a permanent gauge. It shows the procedure in the manual if you have one.

Attached Thumbnails

 

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1983 300SD
200000miles

Harbor Freight also sells a combination Vacuum/Boost Gauge.

The Gauges to mount on the Dash Board will look similar to Oil Pressue gauges are Voltmeters are are about 2 inches in diameter.

Just for test purposes any Gauge that goes up to 15-20 psi would work.

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84 300D, 82 Volvo 244Gl Diesel

I put a manual boost controller on mine, solved the weak wastegate spring. Could only achieve 0.7 bar max without it, now I get as much boost as the turbo is capable of but have set to controller to let go at about 1 bar.

Aware of the danger, I added a boost gauge monitor in the car (at eye level) with a bright blue LED that goes off if the boost goes over 1.1 bar. I have disconnected all the over-boost protection lines and solenoid on the car to clean it up.

Remember, diesels only need as much boost as needed to burn available fuel. Overboosting adds no more power beyond that point.

I also have my ALDA off, I find the faster turbo spool up and higher release pressure offers more air to help properly burn what would otherwise be black smoke coming out the end. That results in more power... as in I can squawk the tires on this baby.

So... I suggest if you have sans-ALDA and do find yourself blowing black check your boost levels. If sagging, add a manual boost controller. $20 ebay. It's a brass T and spring and ball valve.. You'll need to toss the hose barbs that come with it and gets ones that fit Mercedes hose on the wastegate.

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Cheers!
Scott McPhee

1987 300D