Hi - new to forum... and Benz... and diesel... just new.

Just bought beautiful 85 300SD 5-cyl TD. Has 150k miles. Runs great but sometimes loses power when I try to accelerate - could be from a stop, could be up a hill, could be in the middle of a nice strong acceleration and all of a sudden the engine starts to stutter and putter, running rough and it can barely move.

I have a feeling it is somehow associated with turbo (is there a waste gate on these?) but not real sure. Anyone had any experience with this or might have any suggestions?

Looking forward to being the owner of this awesome car... I hope! I hear that they run forever!... if you take care of them, that is.

 

Read the discussions about the car running on 3 cylinders.

 

Use good German filters like Mann or Knecht. Don't go to NAPA or Pep Boys and use their "Made in India" crap. Go to the dealer and pay more if you mustbut use the good stuff.

* Tip For New M-B Diesel Owner *
Put cardboard under the engine and get plenty of rags -- you will spill fuel during this process. Make sure to loosen the 22mm bolt on top of the spin-on filter to make removal easier, and remember to use the manualplunger (round, white plastic) on the injection pump to re-pressurize the system before attempting to start the engine. A good 35-40 strokes of the plunger usually does it.

Have fun.

 

DRRTY240D, Thanks for the tip. Am about about to change my fuel filter can you described the injection pump re-pressurization please. How do you use the manual plunger and were is it sold. Thanks hope to here from you soon.


Tip For New M-B Diesel Owner *
"remember to use the manualplunger (round, white plastic) on the injection pump to re-pressurize the system before attempting to start the engine. A good 35-40 strokes of the plunger usually does it. "

 

I am having a similar problem with my 83 300sd. It runs great for anywhere from 5-25 miles, then it starts to build up air pressure in the fuel injection system. This causes it to starve itself of fuel and eventually die. I can let it set for a few minutes and it will fire up and run again. My primer pump leaks, could it be sucking in air and causing this problem? Any other ideas? I have changed both filters and checked the tank strainer.

 

There is a small rush of air when I take the cap off. I have tried driving without the fuel cap, but it doesn't help. I also tried blew air through the return line to try to clear it out if it was clogged. Where is the vent valve located?

 

The vent is a small bell shaped thing under the car, ahead of the axle, if I remember correctly.

About using the primer pump. If you have the white one, you need to unscrew the plunger, then once it's free, you repeatedly pump it until you can see the fuel in the clear lines, and then usually hear a quiet buzz (?) in the main injection pump, as the pressure regulator vents the fuel to the return line.

On the newer design primer pumps with a smaller black cover, you just push down on it to pump. It's spring loaded and will pop back up on it's own.

 

Here is what I do.
1) Fill the car full of diesel and a spare can.
2) Drive home and back the car up on ramps
3) completely fill the tank up
4) Then change the fuel filter (Both primary and secondary screw type).
5) Then pump the primer

To ensure your fuel line or the screen in the tank is NOT plugged, take the cap off the gas tank first, I put the air compressor to apr. 15 psi (so not to blow out the fuel lines), and take the fuel line off of the in line filter and blow the fuel back into the tank till you hear it bubble. (only warning is you may blow fuel out the gas fill cap if you have already filled up the fuel tank).

 

I assumed the primer pump worked like other primers I've seen - you pump it until you see fuel coming out and then it is done - that's what I've been doing. Seemed to work OK although it still needed restarting a couple of times. Is that wrong, and I need to replace? car still runs fine.

I need to do this relatively oftenbecause my veggie oil filter gets blocked a lot quicker than diesel.
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