1983 300D Turbo Boost Improvement Next Steps

At ca. 154,000 miles I have been slowly bringing the engine performance back to snuff. I recently rebuilt my turbo using your excellent kit. The compressor and turbine blades and shaft were in excellent condition so I opted not to purchase the replacement set.

Prior to the rebuild my boost pressure at 4000 rpm was 9 psi. Following the rebuild, there was no improvement in boost pressure. Per your instructions, I tested the waste gate (with a bicycle pump) and it appears to work.

The ALDA tube and Banjo bolt are clean; I've installed a new air filter, adjusted the valves following your instructions, installed rebuilt Monarch fuel injectors, and did a diesel engine purge (which was clean) and replaced the fuel filters.

Is 9 psi within the acceptable operating range? Based on my reading of your manual this is low, but I am unsure as to additional steps needed to increase the turbo boost.

Thanks for your help, Scott

P.S., the Monarch injectors gave a noticeable improvement in smoothness.

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

Recommendation

Hi Scott, you did not say if you tried to adjust the spring pressure in the waste gate to increase boost? What are the performance symptoms of your engine. Does it still feel "doggy." :-) Kent

I have not tried to adjust

I have not tried to adjust the waste gate spring pressure. At first reading of your manual, it was not clear to me whether adjusting the waste gate would be more beneficial compared to increasing the fuel richness by adjusting the ADLA setting, which I have not yet tested. The latter appears easier :)

Overall the car drives substantially better than when I purchased it. The only time it is sluggish is when going uphill, or when the engine is cold, and there is no noticeable turbo "kick". The turbo pressure increases gradually with increasing engine rpm, peaking at 8.5 - 9 psi at 4000 rpm.

Waste gate adjustment

Kent,
At the risk of asking a foolish question: I've spent the last two evenings trying to remove the spring clip to allow adjustment of the waste gate. I have been unable to access the clip end to lift it with a screwdriver or pick. I have also been unable to rotate the clip to gain a better angle.

Are there any tricks-of-the-trade to facilitating this task? I am reluctant to disassemble the turbo again, which seems excessive for a boost adjustment. Any advice, or suggestions for an alternate approach, would be appreciated. Scott

Suggestions

Remove the air cleaner and thoroughly clean the waste gate housing before you begin. It is very hard to see what you are dirty if there is oil and grime. Get a good light and use a mirror if you need to. Sharp pointed pick tools work even better than small screw drivers. You will need two picks. Put a straight pick up along the edge and rotate clockwise around the waste gate housing until you feel the tip of the pick catch the notch in the end of the coil spring clip. Pry out with that pick and insert another pick further down to aid pry the end out of the groove. Once you get the end out continue to move the second pick around in a clockwise direction. If you can not find a notch at the end of the spring it means it was probably broken off at some point. Then you will need to sharpen the points of those pick tools - place both tips close to the broken spring end and pry out hard.

Update

Thank you for the advice, it helped quite a bit. The tab was located at an angle that I could not access with the straight pick. I wound up grinding the curved pick (from the turbo rebuild kit) a little flatter to fit under the tab.

It actually took me longer re-installing the clip after adjusting the wastegate. I would nominate this design to the same designation as the glove box liner - horrible.

I adjusted the set nut three full turns, which increased the boost to 10 psi. And that is where it will stay, since I don't wish to spend this much time again for another 1 psi boost. --- Scott