Help with smoking 240d!

Hi All :

I picked up a 1981 240d 4spd manual (w/230k on the odometer & 100k on the engine) a few weeks ago for a commuter car. I've done the nuts & bolts work and now it's time to deal with the big problem ... SMOKE! I might be spoiled by my '02 TDI, but this Merc could be used to hide a battleship ...

Engine-wise I've done just the basics including valve timing, new injector nozzles, flush + new filters, etc. But even running b100 it smokes like a champ.

I don't think it's burning coolant as there's no oil in the radiator & the "smell" isn't right. I can't tell though if it's burning engine oil since I haven't had it long enough. Even with a fresh shutoff valve it doesn't like shutting down; could that suggest it's still dieseling on engine oil?

Additionally when I pulled the oil filler cap today after some 70mph highway time (mostly downhill ... this is a 240 after all ) the valve cover was full of vapor. Does this indicate blow-by or that normal for this engine?

Any suggestions would be greatly appreciated. I have a set of valve stem seals and may tackle that tomorrow if folks think it would help.

Many thanks in advance;
Steve A.

[BioPOWER]

By "valve timing" I'm assuming you mean you've adjusted valve clearances? OM61x engines require it every 15,000 mi IIRC...valve guides/seals could be the next step.
Slow shutdown could be attributed to a vacuum leak; shutoff valve is vacuum-operated.

[Kuhlrover]

It would help to know what kind of smoke you are seeing.

White smoke: Unburnt fuel. This can be caused by low compression, bad timing or low combustion temperature. For low compression or low combustion temperature, this is usually worse when the engine is cold or was just started. Other things are bad injectors (spitting instead of spraying) or a worn injection pump.

Billowing white smoke: most likely coolant leaking into combustion chamber. Should smell sweet or like hot antifreeze.

Blueish white smoke: Burning engine oil.

Black smoke: Too much fuel or not enough air: This can be caused by a clogged air filter, timing, IP out of adjustment.

I think at this point you need to do a compression check to see how healthy the motor is. I was at Harbour Freight Tools the other day and see they had an inexpensive diesel engine compression test kit for $30.00.

I also noticed you are in Co. The higher elevation is going to augment some problems. Since the air is thinner, there is less air to compress in the cylinders and therefore it will drop the combustion temperature. If your engine has significant wear, the higher elevation will make this more pronounced.

TimK

[79300sdtd]

Originally Posted by Kuhlrover

White smoke: Unburnt fuel. This can be caused by low compression, bad timing or low combustion temperature. For low compression or low combustion temperature, this is usually worse when the engine is cold or was just started. Other things are bad injectors (spitting instead of spraying) or a worn injection pump.

Billowing white smoke: most likely coolant leaking into combustion chamber. Should smell sweet or like hot antifreeze.

Blueish white smoke: Burning engine oil.

Black smoke: Too much fuel or not enough air: This can be caused by a clogged air filter, timing, IP out of adjustment.

I also noticed you are in Co. The higher elevation is going to augment some problems. Since the air is thinner, there is less air to compress in the cylinders and therefore it will drop the combustion temperature. If your engine has significant wear, the higher elevation will make this more pronounced.

TimK

Tim,

i thought any white smoke was water vapor (coolant or condensation from the cold engine and black smoke was unburnt fuel (incomplete combustion and or too much fuel).

not too sure if the elevation has anyting to do with his problem.

this is all in the sake of knowledge, not bashing you, and i could defiantely be wrong.

[BioPOWER]

Originally Posted by 79300sdtd

i thought any white smoke was water vapor (coolant or condensation from the cold engine and black smoke was unburnt fuel (incomplete combustion and or too much fuel).

White smoke can also be unburnt fuel upon startup. I started my E300 today after it stood (out of the garage) in the rain for a day, and thank God no environmentalists were driving by--it made that much grayish-white smoke. The cause: I have one bad glowplug (stuck), so even after 30sec of preglow it ran on only five cylinders for about a minute, then the idle smoothed out and the smoke went away completely. The engine was cold and produced white smoke, just like Kuhlrover said happens.

Black smoke is also unburnt fuel, but when the engine is warm...the IP supplies too much fuel for the engine to burn so it has to go somewhere. This is why black smoke is most often seen during WOIP Italian tune-ups.

[JimmyL]

I could never tell white smoke from blue smoke or blue/white smoke. The smell will quickly tell you if it is vapor or not, and if vapor it will dissipate much quicker.
Since I ended up having to sell the smoker, I'm the wrong person to give advice on this one. I could list about 10 things that make sense, but don't guarantee it will fix the problem. It didn't fix mine.......

[BioPOWER]

Mine was definitely smoke, not a vapor like gassers produce in cold weather. It did NOT dissipate quickly at all . Mine will even produce white smoke when starting from a dead cold on "relatively warm" days, days when gassers wouldn't produce visible vapor.

[79300sdtd]

Originally Posted by BioPOWER

White smoke can also be unburnt fuel upon startup. I started my E300 today after it stood (out of the garage) in the rain for a day, and thank God no environmentalists were driving by--it made that much grayish-white smoke. The cause: I have one bad glowplug (stuck), so even after 30sec of preglow it ran on only five cylinders for about a minute, then the idle smoothed out and the smoke went away completely. The engine was cold and produced white smoke, just like Kuhlrover said happens.

Black smoke is also unburnt fuel, but when the engine is warm...the IP supplies too much fuel for the engine to burn so it has to go somewhere. This is why black smoke is most often seen during WOIP Italian tune-ups.

that is why i like this forum... ya learn something new every day. i stand corrected

Thanks for the feedback. It's definitely not burning coolant, but I cannot tell if it's blue/white, blue or otherwise. My plan now is to find a video camera & take a poll

Re the poor shutdown good point about it being vacuum-related! This car clearly has terrible vacuum.

I'll go ahead & get the compression tool. What's the consensus on checking via the glow plugs or through the injectors?

Many thanks again!
Steve A.

[Kuhlrover]

Testing through either port doesn't make any difference other then getting the glow plugs removed is a lot easier then pulling the injectors. For the MB's I have seen most of the compression testers set up to test through the injector port. Some of the kits out there sell adapters that allow you to test through the glow plug port but I haven't seen them sized for the MP plugs. I plan on modifying one of these to fit the glow plug threads for a 617 head by welding it to an old glow plug that I have drilled out.

If you find an adapter to allow you to test through the glow plug port, be sure to crack open all of your injector lines. You don't want a cylinder to accidently to fire when your testing. It will blow out the guage. Just wrap some rags around each injector top to catch the fuel.

TimK

[TheDon]

I get gray smoke at night that is only visible under WOT from take off... ^_^

[JimSmith]

Early 240D (1974 and 1975) and the preceeding car, the 220D, had a mechanically driven vacuum pump that exhausted into the intake manifold. The pump has a diaphragm that has engine oil on one side, and if it fails, at idle it will suck engine oil into the intake manifold. Enough to make a thick billowing white cloud. On the road at speed there is no manifold vacuum in a Diesel so the smoking is much less dramatic. Come to a stop though, and you can be lost in a cloud of thick smoke.

I am not sure if the 1981 240D has such a device or not, however, if it does you will be able to see a ~3/4 inch thick nylon tube that runs from the vacuum pump on the front of the block to the intake manifold. The diaphragm is cheap and relatively easy to replace, so, if this is your problem it might be a blessing.

Other than that, smoking from a car that starts well and has power is an enigma. There must be some other aspect of performance that is affected by the smoking, which is either too much fuel or engine oil consumption. Neither is a likely event in an otherwise healthy engine.

Good luck and let us know how the car behaves on the road. Jim

[merrycran]

OK, I know this is an old thread, but I'm hoping to narrow down my smoking '79 240d problem.

It does smoke on cold startup, which is normal and I'm not concerned about, but even at 180C after an hour's drive, it smokes white visibly. I run it on a biodiesel blend, and it does not smell like oil. I have had the valves adjusted, new glow plugs, old leaking injector lines replaced (granted, with some nice used ones), the radiator flushed and pressure tested. Oil changes regularly, and even the gas cap and oil cap replaced. I'm pretty sure at this point it's unburned fuel, but what else can I do to test and/or fix it??

Originally Posted by merrycran

OK, I know this is an old thread, but I'm hoping to narrow down my smoking '79 240d problem.

It does smoke on cold startup, which is normal and I'm not concerned about, but even at 180C after an hour's drive, it smokes white visibly. I run it on a biodiesel blend, and it does not smell like oil. I have had the valves adjusted, new glow plugs, old leaking injector lines replaced (granted, with some nice used ones), the radiator flushed and pressure tested. Oil changes regularly, and even the gas cap and oil cap replaced. I'm pretty sure at this point it's unburned fuel, but what else can I do to test and/or fix it??

Are you losing any coolant?

[merrycran]

I don't think so ... I thought this might be the case at first, hence the drain/flush and pressure check. They said it was OK ... it was done last summer, and I haven't had to add any. The coolant is at the bottom of the 'T' with cold engine ...