I am working with a friend trying to get his 300SD to start and idle smoothly. So far I have adjusted the valves, replaced the injectors and glow plugs and run a couple cans of diesel purge through it. The car sounds like it is missing on the #5 cylinder when it is first started and it smokes (I'll swear it looks white). I have started it cold and loosened the #5 injector line and there was no change - it continued to run badly. When I do this with the engine hot it does idle poorly like it should with an injector lined pulled. He just purchased the car off of ebay (160k miles thereabouts) and I have not seen any service/maintenance records. I have noticed too that someone has the idle cranked up to around 800-900 rpm. The car runs good on the freeway (don't they all ) but something is not right at idle and during cold starts. Another thing is that I suspect someone has installed a "drilled out" thermostat. The temp never gets above around 80 dC even when the engine is loaded. When I replaced the injectors there was quite a bit of liquid oil around the "barrel" of the injector. In addition, the glow plug holes were severly sooted - I had a hard time getting the reamer in there. The timing chain is stretched to the point where the crank is at 11 degrees past TDC when the cam is lined up. I will probably try to do a "drip" timing test on it over the next week or so too.

I am going to try to run a compression test this weekend. Could the fuel injection pump need calibrating? I am thinking that there may be a head gasket issue. I may try to keep if for a few days and observe some of the other signs that show head gasket problems.
thanks

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Jim

Jim:

You have more knowledge about these cars in your little pinky than me and my friends combined. But here are my thots:

1. If I add two of my cars together, I have the same symptom. The idle was merely a rack pin.

2. The smoke issue does seem to be related to timing. So I'm with you there. I've not done the drip test but suspect that the chain is major stretched. What baffles me is that the car starts in cold weather beautifully and idles well. Its just that it smokes to high heaven. I mean, I can lose the car in the stuff (but only at idle or between shifts (manual).

Good luck

Don

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DAILY DRIVERS:
'84 300DT 298k (Aubrey's)
'99.5 Jetta TDI IV 251k (Julie's)
'97 Jetta TDI 127k (Amber's)
'97 Jetta TDI 186k (Matt's)
'96 Passat TDI 237k (Don's
'84 300D 211k Mint (Arne- Undergoing Greasecar Conversion)

SOLD:
'82 240D 229k (Matt's - Converted-300DT w/ 4 speed

I know for certain that there are more than a few things that can make these old diesels smoke.
Two weeks ago I worked on my brother in laws 81 300D. He said power was down, hard starting, and smoky as all get out.
Found three failed glow plugs. Then checked and found the pressure line going from the rear of the intake to the cross-over and down to the ALDA was plugged everywhere. Cleared all the lines and the power returned.
The trans was flairing so bad it felt like it was shifting into neutral between gears. Adjusted the module counter clockwise and it shifts just fine now.
As a note the chambers where the glow plugs go in were badly gunked also.
All that taken care of. He has been driving daily for the last two weeks and called last night. Said the smoke has mostly cleared up now. A little at start up and he no longer feels he needs to sneak out of his sub division.
Go figure.

Old dies,

Did this car have a turbo? My daughters '81 has no turbo. What module did you turn to make it shift better?

Have a great day,

Yes it was turbo. Come to think of it not sure that it wasn't a 1982 model.
I followed the procedures outlined in Steve Brotherons article about tuning the MB transmission. Don't have that reference here at this time, but it is passed around a lot on this forum.
There is round plastic module that mounts on the left side of the transmission. The vacuum line attaches there. Pop off the center cap and there is a small metal part in there. Pull it out and turn it counter clockwise about 1/8 turn and test drive the car. It took 1 1/2 turns to get this beast shifting correctly. We also cleaned the vacuum regulator mounted on the rear of the IP. The basic test there is to pull the vac line off there and test drive. If the shifting improves, then that is a problem and needs repair, or cleaning. It more of less 'leaks' vacuum to change the shifting patterns. I found that cleaning the orafice with warm soap worked.

Did you test the injectors before installing?? I've heard of bad injectors right out of the box.....

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Orland Park, IL
1985 300SD 215,000 miles

White smoke is raw atomized fuel usually from a cylinder that is not firing.

P E H

The temperature not getting up above 80 dC was really bothering me so when I got home this evening I pulled the thermostat cover off and THERE WAS NO THERMOSTAT. I could hardly believe it. I put a 80 dC thermostat in and took her up on the freeway. Loaded it up at 80 mph and it rose to around 95 dC and then dropped down when I slowed, exactly like it is supposed to.
Prior to putting the thermostat in I started it and it started immediately (good glow plugs/compression) and then it began it's rough idle and smoke thing. I'm wondering if maybe the pre-chambers are full of soot because of having run cold for so long. What do ya'll think? Has anyone ever seen clogged up pre-chamber holes? The car smooths out and runs fine after it is up to temperature.
I plan on checking the injection timing this weekend.
thanks

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Jim

That is not so far fetched a thought. If you could get some of the good treatments, like Stanadyne Performance, or whatever, maybe that would be an economical way to speed up a clear out the buildup.
I would think that with this engine running cold for an extended time the buildup of stuff in the cylinder would be significant.

Jim:

11 degrees is beyond limit for chain stretch (8 is replament time), so get a new chain in there before you play with the injection timing, or you will have to do it again.

Late valve timing gives low power and lower effective compression, and combined with late injection timing will give poor combustion, resulting in sooty pre-chambers and unburned fuel deposits. So does running cold all the time! New chain and a nice drive will fix all that. Lots of soot and oil can make the rings stick, lowering compression in any cylinder where they are well stuck.

Rack pin spring trouble usually shows up hot, but if it is really bad, could affect cold running too. My bet is that #5 is just low enough on compression that it won't fire cold.

That said, a leaking pressure valve or pressure valve holder seal could produce exactly your symptoms -- especially true if you get normal amounts of fuel leaking off with the cap nut loose but no injection. My 300D, however, didn't smoke at all, so I suspect timing to be most of the problem.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

This is exactly what I am seeing. I will get a new chain in there and see what happens then - I'll keep ya'll posted.
Jim

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Jim

Did a compression check today and it was 250+ psi on all five cylinders. Next step will be a new timing chain and then will see how it starts up cold. Car runs great when it is up to temp and combined with the compression numbers I really don't think it is anything serious.

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Jim

Were the compression test numbers with a warm (operating temp) engine or cold, 250+ is on the low side of spec,are you going to do a cylinder leak test?

The numbers were on a hot engine.
I will probably do a leak down test next time the car is over here and AFTER x-mas. Seems someone wanted my air compressor worse than I did and removed it from the premisis one day when we had driven off and left the garage door open. I am thinking Santa is going to bring me a new one.

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Jim