I am working on a 87 turbo diesel 603 motor in a 124. Complaint is on cold start engine starts up runs rough and dies. It may take 3 or 4 tries to keep it running, depending on ambient temperature. After start up you get a lot of whitesh maybe little blue smoke, but smeels like raw diesel fuel, incomplete burning. It takes a good while for the smoke to clear up, but really never goes away completly. After the car is warmed up it runs good. The cars has 300,000 miles on it. The glow plugs were replaced at another repaire shop under customer request, this did not make any changes. First I did a compression test I had readings of 475, 550, 550,525,475, and 500 psi. I thought this was acceptable. I did the compression test at the injector nozzle ports so while I had the injectors out I bench tested them, A couple of them did not have a good pattern. Customer wanted to replace the set so I put in a set of rebuilt, the all looked good on a bench test, no improvment. next I checked pump timming it was at -17 deg, I advanced it to -13 deg no change in running. When I had the injectors out I did a visual of the glow plugs, they were all getting very red. Hooked up a alternative fuel supply this made Know differnce. Checked cam timming, to my surprise it was really close to spec. Checked EGR valve and bypassed it to make sure it was noy coming open, no problem found. Removed intake to see if the intake valves were carboned up, again I was surprised they were cleaner than I expected. At this point I suspectd a injection pump , put on a rebuilt MB pump, no change. I tried advancing the timming of the pump to -10 deg no change. I have not seen any indication of air in the system, and the car never has long cranking it fires right away , but like I said earlier it will run ruogh for about 15 maybe 20 seconds and die. I pulled the 50 circuit wire from the glow plug relay connector so they would continue to glow after start up , this seem to help some. Car uses about a quart of oil every thousand miles and as had no coolent loss. Any info may help. We are thinking it might be somethig mechanical, but have not pulled the engine apart at this time.

jbrowning73,

Have you checked the condition of the prechambers? If the car was running for a long time with injectors with a poor spray pattern it is feasible the prechambers are damaged or the venting holes are clogged. It would seem whatever you are experiencing results in non-combustion in more than one cylinder, leading to stalling and expelling unburned Diesel fuel. It may also lead to early damage to the injector nozzles and or the seal discs that fit in the bottom of the prechamber. Have you checked the injectors again?

I would be surprised with the compression figures you cited if there is a mechanical problem. It would seem the valves and their timing is ok, both by your checks and the compression values.

When was the last time the fuel was checked? How are the filters?

Sorry I can't be of much more help, but it seems the problem should be in the prechamber, injectors, or fuel. Good luck, Jim

__________________
Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

What is the idle rpm when it's rough?

How are you checking IP timing? I don't know the actual start of delivery spec but the position of the crank pulley when the governor lug is visible through the inspection port is 14-15 ATDC.

How are you checking compression? My manual says the max is 465psi.

And a question to ask of anyone working on a 603, does the cooling system remain pressurized after you shut off the engine? Even hours after you shut off the engine?

Sixto
91 300SE
87 300SDL
83 300SD

Jim
Thanks for the input. I have not looked at the prechambers, other than looking through them in the head when I had the injectors out. I have not had the rebuilt injectors back out since they were installed. As for the fuel , I took a gallon container of fresh fuel and plumbed it directly to the siphon pump, this bypassing the fuel in the tank and any lines or hoses associated with the fuel heater. As for the compression test, I was using the motortronics gauge ( I believe that is the correct name) it is the approved tool by MB. I also thought those reading were high according to my manuals, and it said a max deveation of 3 bar which I exceeded that, but I thought that if those reading were accurate it has enough to run.

sixto thanks for your reply read what I replied to jim if any other I deals they will be appreciated. I wanted to finish the story. I puuled prechambers, pulled cylender head, and inspected combustion chambers, no problem found. Replaced engine with remanufactured long block, car ran great. Customer is happy and car is gone end of story.