Hello

I have a 1967 200D with the OM621 motor and 175K miles that is having an issue with white smoke. I get a lot of white smoke when first started, but idle smoke seems to get better after it warms up. Even after warm up it will kick out a puff of white if I downshift or let off the accelerator while the motor is loaded. I have recently replaced the injector nozzles to see if that would help but it doesn't seem to have made any change. I did buy a pop tester and have all 4 firing at around 1650-1700 PSI. I have been battling leaks at the injectors for a few weeks but finally have all of the leaks stopped.

Any ideas on what to try to cut the white smoke would be greatly appreciated.

Thanks

Are you having to add coolant?

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Jim

No coolant loss

I know this isnt good news since you just got the injectors to stop leaking...
But compression test?
Valve stem seals?

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
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Late injection pump timing can cause white smoke.

When you remove the cap from the coolant tank does it smell like combusting gasses?

Could it be some bad fuel? Try filling up at a different place.

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84 300D, 82 Volvo 244Gl Diesel

I finally got some time to work on the smoke issue this weekend. I started by changing out the diesel filters and running 2 cans of diesel purge through the motor. No improvement in the white smoke. Next I checked valve clearance and found about 1/2 of the valves needed some adjustment. While I had the valve cover off I checked the timing marks and found I it showing 6 degrees off the 0 mark. Is this enough chain stretch to justify replacement of the chain? Would this potentially cause the white smoke on downshifting? I also noticed the hose that runs from the vacuum pump to the throttle got into the fan and has some nicks. Not sure if that could cause smoke? Any advice is greatly appreciated.

Also - I am not noticing any major oil use so I don't think this is valve stem seal related. Definitely seems like un-burnt diesel smoke vs oil or coolant smoke.

Finally getting a chance to work on the smoke problem again. I decided to set the valves again and there were a few that were tight. I also found a leak in the vacuum line that goes from the vacuum pump to the intake manifold, and replaced the line. i also checked the valve timing again, with the dial indicator method and is is 5 deg behind TDC. Still smoking after all that so I decided to check compression today and got the following readings starting from the front (290, 320, 280, 265) PSI.

I have a 3 deg offset woodruff key on order to get the timing back where it should be, so that will be my next thing to try.

Do the compression numbers bad enough to cause this issue? To recap - lots of white smoke at startup that goes away when it gets warm. It also kicks out a big white puff of smoke when I downshift or let off the throttle while at speed, even after it has warmed up. No coolant use and minimal oil use.

Thanks

OM621 uses the PES4M type injection pump. This pump was also used on OM615 and OM616.916.

Vacuum leaks in the governor system will cause over-fueling, white smoke that smells of unburned fuel. You should check that the governor at the rear end of the IP holds vacuum.

Common leaks:
- Diaphragm; and
- The shaft that runs through the rear part of the governor housing, the so-called poppet cam shaft, or adjusting shaft.

http://www.peachparts.com/shopforum/diesel-discussion/410426-parts-pneumatic-governor-om615-om616.html

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

I am not sure about the chain life on your engine. On the later engines you can get an offset woodruff keys to bring your valve timing back to spec. I don't know if that is possible on yours.

If you cannot change the valve timing you can change/re-time the fuel injection pump.

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84 300D, 82 Volvo 244Gl Diesel

There shouldn't be a hose running from the vacuum pump to the throttle. If your car has one please show a photo of it.

There is a hose that runs between the injection pump and the throttle body, and if this hose has leaks in it then the governor will not function correctly leading to over-fueling. On later cars (W115 220D and 240D, and early W123 240D) this hose is not located near enough to fan to be damaged by it, as it runs from the rear end of the injection pump around the back of the valve cover on its way to the throttle body. Perhaps your car's routing of this vacuum line takes it around the front of the engine instead.

And as noted above there are other possible sources of vacuum leaks in the governor system (diaphragm, adjusting shaft).

Your experience with white smoke mirrors mine before I repaired the '74's leaky governor - clouds of smoke on cold start-up that improves when the engine warms up. I went a little further than that, and almost destroyed the engine driving the car from Utah to New Mexico (melted pre-chamber that thankfully did not drop pieces into the engine).

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

Hi

I will try to post some pics when I get home, but there definitely is a line running from vacuum pump to the intake manifold. I should probably mention that I think the original owner had the motor replaced at some point. The owners manual had a hand written note that said new motor 55k miles. It appears to be an OM621 but may not be a 1967 model.

Thanks

Yep, I was wrong. I looked at my car and yes, there is a pipe running between the vacuum pump and manifold, but not to the throttle body. It's a filtered connection to keep dirty air out of the vacuum system. Holes in that pipe should have no effect on the injection system, but it is a good idea to repair or replace your damaged one.

The injection pump governor uses another pipe/hose that runs to the rear end of the injection pump from the throttle body. On your car it might be a steel pipe.

Yes, some photos could be helpful.

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- Greg -
1973 220D, The Prodigal Benz
1974 240D

I'm having trouble figuring out how to post pictures, but I do have some tubing that runs from the throttle body to the IP. It appears to be made of a hard plastic material, and I don't see any cuts or breaks in the tubing. I have replaced the rubber hose that runs from the vacuum pump to the intake manifold so it should be good.

I will see if I can put a vacuum test rig on the hose running to the IP to see if holds vacuum. Also my offset woodruff key and valve stem seals arrived in the mail today. I started prep for the woodruff key install on the camshaft gear this weekend, but had to order a new seal for the timing chain tensioner from Lithuania, so it may be a few days before I get everything back together for a test. While I am waiting I put some marvel mystery oil in the cylinders in case I have some sticky rings. I am throwing the kitchen sink at this car, as I really love driving it, with exception of the smoke screen....

Thanks for all the good sugestions on what to try.

Also forgot to mention that I did check the diaphragm on the vacuum pump, and it was good. I have 3 spare diaphragms that I found on Ebay if anyone is looking for one.

Thanks