84 300D extra smoke - cylinder down

[lineman]

Hi -

My girlfriend has a 1984 300D which she really likes, but it recently started producing quite a bit of white smoke, even at idle. The smoke smells like semi-burned diesel.

There is no oil in the coolant or anything weird like that, so I tried disconnecting the fuel lines, one at a time. When I disconnected cylinder number four, the engine did not run any worse, even though fuel was squirting out of the line. So it appears that the problem is that the fuel is not burning in this cylinder.


Any idea what can cause this, and what my next step should be?

[myssrhl]

mine had a bent connecting rod. though could be other causes just threw this one in.

[GRIESL]

Valve adjustment? Bad injector? I'd try these cheap things first.

[winmutt]

White semi burned is usually due to premature injection. Black is partially burnt. Does it still happen when the engine is warm? Pull the injector and have it tested. Also check to make sure you PC ball is there. I am betting it is a shot injector. I have a friend who might be selling one for less than retail if you need it.

[SD Blue]

Originally Posted by lineman

.......... When I disconnected cylinder number four, the engine did not run any worse, even though fuel was squirting out of the line. So it appears that the problem is that the fuel is not burning in this cylinder.


Any idea what can cause this, and what my next step should be?

Sounds like you found the problem......a faulty injector. How much do you DIY? Remove (all 5) and take them to a good diesel injection shop and ask them to ultrasonic clean and check for spray pattern and pop pressures. Sometimes just cleaning takes care of it or it may need to be rebuilt. (Buy new heat shields for reinstallation.)

[lineman]

I had a compression test done and Cylander # 4 has no compression.

I don't have the ability to replace the engine, should I just give the car away at this point?

It still drives but doesn't have much power and makes a lot of smoke.

[pawoSD]

Originally Posted by lineman

I had a compression test done and Cylander # 4 has no compression.

I don't have the ability to replace the engine, should I just give the car away at this point?

It still drives but doesn't have much power and makes a lot of smoke.

No compression at all sounds suspicious, have you checked the valve adjustments and such? Compression can be lost because of a valve problem.

[lineman]

Yes, I have checked the valve adjustments and they are ok.

[Caduceus]

Ill buy it if it's in ok shape other than the motor.

[SD Blue]

Hmmm...."zero" compression does sound very suspicious of the testing process. With a cylinder at zero compression, the engine would seem like it was shaking itself to death. Are you seeing this?

I was under the impression that it just seemed a "little rough" and you had some smoke.
The questions I would ask are:
Does it lose any coolant?
How much oil does it use?

Answers to these would go a long ways toward determining the quality of the compression test.

[pawoSD]

An engine with "zero" compression on one cylinder would also have an ENORMOUS amount of blowby and oil consumption....as tons of oil/fuel vapors would be getting into that cylinder, as 0 compression would mean total loss of seal between the piston/rings and cylinder wall. All the air being compressed on each compression stroke would be exhausted into the crankcase and out the breather tube on the valve cover....which would also cause a lot of oil loss due to the vapors blasting out that way.

Does the engine have much blowby, and does it consume a lot of oil?

[JimmyL]

Originally Posted by Caduceus

Ill buy it if it's in ok shape other than the motor.

...........And the vulture swoops in.......

[vstech]

you could also have a badly burned exhaust valve in that cylinder. this would show very low compression, and have little blowby. a leak down test would confirm this. I would take it to another shop and have them do a compression test to get a second opinion.
and do another valve adjustment on that cylinder too, gunk can get on the valve face and mess up the adjustment, so do it, run the motor, then do it again.
you could also have a flat cam lobe on the intake valve.

[lineman]

My friend has a really nice engine for 850 and another friend will do the swap for 550, looks like I'll be going that route.

[pawoSD]

I'd still try and figure out whats wrong with your engine. Would be a shame to waste a perfectly good engine over something potentially simple.