I'm Getting Frustrated - Still runs like Crap! - PeachParts Mercedes-Benz Forum

Jmana · #1 05-19-2007, 11:46 PM

I don't know what is going on with my 87 300D. The symptoms are as follows: Lot's of white smoke, even when warm, which reeks of unburned diesel, engine feels like a gasser with a bad miss, seems to not have as much power as it should, and doesn't get great mileage. It starts right up every time though. I took it to a shop, and they told me they thought it was a bad injector, so I pulled them all and took them to get pop tested. The guy said all were fine but one, and that one cleared up when he increased the pressure to it. There was a buildup of hard black carbon on the end of the injectors, so I cleaned that off and put them back in. No change. So then I figured I'd better check the timing chain, which I had replaced about 6 months ago. It was right on. Checked the injection timing, the mark was right on at 14 degrees ATDC. So at this point I pulled the injectors again, and sprayed some PB Blaster in the prechamber then filled each one with Seafoam. I also had to clean off even more carbon from the injector, although this time it was much softer and easier to remove. Put everything back, and again no real change. So now I am a little annoyed, and buy a big container of Marvel Mystery Oil and hook up the fuel lines so it runs straight on the stuff. Didn't see a whole lot of black smoke, but it did run pretty smooth while on the MMO. But now it's back on diesel, and back to running like crap with lots of smelly smoke. What else should I be looking at here??

300SD81 · #2 05-19-2007, 11:50 PM

Which method are you testing the injection timing? The drip method should be 26 BTDC

Jmana · #3 05-20-2007, 08:41 AM

By looking at the notch in the hole in the side of the IP.

Brian Carlton · #4 05-20-2007, 12:19 PM

Quote:

Originally Posted by 300SD81

Which method are you testing the injection timing? The drip method should be 26 BTDC

There is no drip method for an OM603. And the spec for the 617 is 24BTDC.........not 26.

Brian Carlton · #5 05-20-2007, 12:20 PM

Quote:

Originally Posted by Jmana

I don't know what is going on with my 87 300D. The symptoms are as follows: Lot's of white smoke, even when warm, which reeks of unburned diesel, engine feels like a gasser with a bad miss, seems to not have as much power as it should, and doesn't get great mileage.

I think it's time for a compression check.

estod · #6 05-20-2007, 04:44 PM

Are you sure the turbo is working? Sounds like not enough air .....

Jmana · #7 05-20-2007, 05:56 PM

I'm not positive it's working, what's the easiest way to check it?

Jmana · #8 05-20-2007, 09:13 PM

The more I think about it, I don't think it could be a compression or turbo issue, because it runs fine on vegetable oil. In fact, I can tell when switching over to veggie when all the diesel is out of the IP by the way the engine quiets up and stops smoking and stops the nailing/missing noise which it makes on diesel. So I am almost positive this is a fuel issue, but if it's not the injectors or the timing, I don't know what else it could be. I can't imagine the IP is going out if it runs good on veggie, I would think that because it is thicker that vegetable oil would make any IP weakness even worse. Although the vegetable oil is being pumped into the IP at a much greater pressure than the diesel, but still that doesn't seem like it would affect anything. So I guess the key to my problem is figuring out what mechanical issue would be more evident when running the vehicle on diesel fuel.

firemediceric · #9 05-20-2007, 09:28 PM

Quote:

Originally Posted by Jmana

The more I think about it, I don't think it could be a compression or turbo issue, because it runs fine on vegetable oil. In fact, I can tell when switching over to veggie when all the diesel is out of the IP by the way the engine quiets up and stops smoking and stops the nailing/missing noise which it makes on diesel. So I am almost positive this is a fuel issue, but if it's not the injectors or the timing, I don't know what else it could be. I can't imagine the IP is going out if it runs good on veggie, I would think that because it is thicker that vegetable oil would make any IP weakness even worse. Although the vegetable oil is being pumped into the IP at a much greater pressure than the diesel, but still that doesn't seem like it would affect anything. So I guess the key to my problem is figuring out what mechanical issue would be more evident when running the vehicle on diesel fuel.

I've read that the signs of a failing I.P. are often masked by the thicker veg. oil making up for the loss of tight tolerances.

TOPGUN · #10 05-20-2007, 09:38 PM

Could It Be A Bad Load Of Diesel Fuel?

Jmana · #11 05-20-2007, 09:53 PM

No bad fuel, it's been doing this for 5 months.

Jmana · #12 05-20-2007, 10:01 PM

If it is the IP going bad, how hard are they to replace? Also, will one out of a 91 350SDL work in an 87 300D? They look the same, but the part number is slightly different.