1991 350 SD no boost

[Benz124s]

Hi All,
I have a '91 350 SD with 168 K miles and no real prior service records before I bought it two years ago. Recently, I had the turbo rebuilt due to lots of axial play in the shaft. Upon reinstalling it, I've found that it will not boost up like it did before. The car starts very easily, but is very slow and will hardly go up any hills. The turbine spins easily by hand. I double checked and it appears I have connected everything up correctly. Any thoughts? I've not worked on very many turbo chargers in the past but removing and reinstalling this seemed straightforward.

Thanks,
Dave

[dieselbenz1]

Have you connected the waste gate controller?

[Benz124s]

Hi,
I connected the arm going to the wastegate, but it seemed kind of a tight stretch to get the rod from the actuator over the pin. Should it have easily slipped over?

Thanks in advance,
Dave

[Benz124s]

Just wanted to say I looked at the car again and still can't see anything obvious as to why it won't boost up. Should the rod from the waste gate actuator easily slide over the pin that connects to the door? I had to pull pretty hard on it to get it to slide over the pin.

Thanks in advance,
Dave

[JamesDean]

Does the 350SD use the same type of vacuum based waste gate control as the 91 300D 2.5?

[Benz124s]

I attached a picture of the one on my 350 SD

[compu_85]

The 350SDL/L have a normal pressure type wastegate, no computer control.

Check that none of the vacuum lines between the intake and ALDA are plugged, including the overboost protection solenoid, and that there are no leaks.

-J

[Benz124s]

Update: I found a line not connected to the EGR vacuum transducer after reading over a vacuum diagram and now the turbo will boost up. Is there an easy way to hook up a Mity Vac or some other gauge so I can see what kind of pressure this thing is set at? The previous owner had the turbo about before and I'm not sure if the waste gate rod was moved or not. I've searched on the forums but didn't see anything specific as to where to T the gauge into the system. Thanks!

[JamesDean]

The MityVac is for vacuum so it won't be of much help. You're going to want a boost pressure gauge. On the 602 there is a plug on the intake manifold that you can put a barb in and connect up to..The 603 might have it too.

[funola]

Originally Posted by JamesDean

The MityVac is for vacuum so it won't be of much help. You're going to want a boost pressure gauge. On the 602 there is a plug on the intake manifold that you can put a barb in and connect up to..The 603 might have it too.

That's what I though also but apparently some models of MityVac can be used to generate both vacuum and pressure.

[dude99]

Yup, my mityvac will read\generate vacuum or pressure

[Hit Man X]

Originally Posted by compu_85

Check that none of the vacuum lines between the intake and ALDA are plugged, including the overboost protection solenoid, and that there are no leaks.

-J

The overboost 'noid was the issue on my SDL. Once bypassed car ran far better and once I gutted the catalyst it really ran well.

[bsmuwk]

Do NOT apply vacuum to the pressure actuated wastegate or you WILL rupture the diaphragm.