After a Decade the car is running but Rough at low idle and white smoke
 

85 300D

So I did it... It's running... but...... rough at idle and white smoke... roughness goes away at 2000 RPM

There are a good number of things that can cause that:
Valves out of adjustment
Bad motor mounts
Worn injector nozzles
(These three are very probable if you haven't already checked them)

Air in fuel
Bad fuel
IP timing being off

Maybe more but these are the easier ones.

A video would help a lot, go ahead and post one when daylight hits.

Here is a video
 

I have a feeling the IP timing is off...

If it's been a decade since it's been running, it could just need some use. Mine sat in a field for 10 years before I got it. Bugs definitely needed to be worked out. Driving helped it a LOT.

Yes ten years inactive is indicative. That usage and even a cylinder soak down may be in order. A compression check after a valve clearance check might indicate the need. Unless the valves clearances where obviously the problem. Specifically the lack of them. Sticking rings are quite common for example after long periods of sitting as well.

So many of these cars never received valve checks and adjustment when needed. In fact hydraulic lifters had already been in existence so long. All too many users of these cars where unaware they did not have the self adjusting valve trains.

Also the concept that the diesel engine needed no maintenance was taken too far. Yes requiring less maintenance than a gas engine perhaps but still there are things that needed periodic checking and sometimes attention. Plus some things naturally deteriorate with age. When you take on an old car expect to play catch up on lot of them.

To me they are a car you can learn on. They are very low tech but quality built at the time. Plus the support of this site helps substantially . Basically it is almost pointless to start trying all kinds of things unless you have reasonable compression either measured or indicated otherwise present in the block.

Then you move onward the same as a good professional mechanic does. You are establishing a baseline on the engine to work from. Expectations that a car sitting unused for ten years will instantly be fine is not too likely going to be a common scenario. Fortunately a lot of common issues with these cars are relatively cheap to address in todays world as well yourself.

This is great advice
 

I agree with you, I have learned so much by working on these cars. I now own 3 of these cars and are restoring them back to as close to factory as I can get.

I will run the compression test and will do this for all my cars.

I might consider dealing with the issue on the posted car alone first. There is a good chance the white smoke is unburnt fuel. If so it should sting your eyes.
Compression issues are generally expensive to deal with if not valve adjustment or the result of sitting too long.

yes, you are correct.... hard to be around the car because the exhaust is heavy and stings the eyes. I have ordered a compression tester and also a IP timing kit.

I had to remove the IP and even thought I followed the FSM to the letter, I think that the IP timing is now off. The reason why is that even though this car sat for 10 years I was able to get it started in about 20 minutes. That's when I noticed the blown freeze plugs and shut down the engine.

During the brief moment it ran, it was running much, much better than it is now..

Well at least you are getting some breaks. If it ran better before you removed and installed the injection pump again. To address the bad frost plug.


Do not forget the valve clearances do not all have to be reset before the compression test. You just have to make sure they all have some clearance when you check them first. Any that are actually tight will defeat any compression check being valid at all. You really want to find clearances at least somewhere very close to what they should be. Or greater.

Do all this stuff that was suggested. then drive it around for a month as ur daily driver, this will clean out all that **** that's built up in your engine and fuel system and cut down the smoke even more

There is so much we leave out. Typically we do not even know what has or has not been replaced over the years on many very old car purchases. Plus if the car was reasonably maintained for a good portion of the previous ownerships. Or not at all.

If you do some fundamental checks as previously mentioned. Although I am not a believer of liquid type repairs. I do believe there is a chance they can clean things up somewhat though as well. Or at least aid in the process.

So in some cases I would add a quart of miracle mystery oil each to the base oil and gas tank. I can see no harm and the stuff is economical. Owners of these cars should replace using the word cheap. I am cheap but it sounds bad. I stretch dollars almost beyond reason sometimes when dealing with old cars.

When driving the car things should improve in a case like yours. Just faster if it is going to otherwise with the solvents. Users of that product for a very long time have proven it can help. Of course it cannot actually fix things. Nor is it totally worthless.

The complication with diesel cars of this vintage. You hope nobody used vegetable oils in a bad way at any time. I have a gut feeling your engine will probably come back on line.

I do not want to introduce you to a wild goose chase. There is a lot to be said for a systematic approach. One important value is you usually do not get as frustrated by doing it that way. Plus keep more money in your wallet.

Many of these engines will not even start after sitting years because of stuck rings. Your first break is it would run. That indicates to me the internals are not in a heavily worn state.

Diesels do not seize as quick as gas engines sitting. I have always attributed this to the normal closer tollerances inside diesel engines. When heavily worn their seems to a tendency to get more moisture involved in the ring lands somehow siting around.

It takes a lot of thermal activity. Expansion and contraction especially of the metals involved to get them to free up. I suspect that is why users find that driving any of these engines after sitting for long periods really seems to help bring them back. Not all of them but a substantial number.

Being a Canadian I suppose I do some things differently. For example if you owned a meter. Set it on the milli volt range. Get the engine running. Separate the plug on the glow plug relay. With one probe on the engine and only on the engine as a ground.. Reading the milli volts with the other probe on all the five terminals individually of the glow plug harness. Is a way to keep a record of how and if things are improving. Recording what you read is best. Can also indicate what cylinders might be weak . Usually best to let the engine warm up before this test.

You have said you want to basically restore three of these cars. Consider this just a tool to help you get there. It is called milli volt testing and has some use in the right hands.

Can also be taken to a level that is complex. In your situation this is not needed. All my engines run really well. I base this on they are terrified of me. Never knowing what to expect if they act up. I do an extensive tune up and general check of almost everything when first purchased as I want reliability.

I learned how to set the injection pump timing and discovered that saying it was way off would be an understatement. Best I can tell about 14° off… Fuel just pouring out of the drip tube I adjusted the timing to the factory recommended one drip per second and the engine is running pretty much normally.

Very very happy about this

Great result. It sounded fairly quiet in the "before adjustment" youtube and the white smoke looked fairly minimal, so I expect it idles great now.