Still problems after doing a valve adjustment - PeachParts Mercedes-Benz Forum

1981_300sd · #1 03-04-2008, 12:21 PM

This is for my 82 240D

A while back I posted a thread about having problems with smoky exhaust and rough idle (engine sounds like it is "missing") when warming up. After warmed up it sounded fine.

I was given the suggestion to perform a valve adjustment.

Now I have done the valve adjustment (every valve was "stuck", took forever to loosen the adjusting nuts). It now sounds better and has more "pick up", but still smokes (blueish hue) a lot while it is warming up and misses a lot. Once warm it performs great and no smoking.

Here is what I have done to try to resolve the issue so far:

valve adjustment
replaced air filter
replaced both fuel filters
ran diesel purge
currently running power service

Any other suggestions?

Thanks!

#2 03-04-2008, 12:29 PM

You should post this in your old thread to keep its continuity. Others searching for answers to similar problems as yours will just be frustrated when they come across threads like that with an unanswered ends.

1981_300sd · #3 03-04-2008, 12:53 PM

The old post went off in another direction, and would not make any sense if I posted there.

I see where you would say that though, thanks for keeping things in check

Bajaman · #4 03-04-2008, 02:21 PM

Glowplugs

1981_300sd · #5 03-04-2008, 03:41 PM

Whoops forgot to mention that.

I have tested the glow plugs as well, I removed each of them and tested with the jumper cable method. All glow bright orange. I then tested all wires going to each plug, and all show a good connection, so the glow plugs are not an issue.

Any other ideas?

vstech · #6 03-04-2008, 03:49 PM

you should re adjust your valves.
seriously overdue valve adjust can result in carbon etc. building up on the valves, adjusting them gets the gunk in contact with the head, and cleans it off, letting the valves get out of adjustment again. re check the valves.

airbus · #7 03-04-2008, 03:55 PM

A compression test might provide some insights.

Ken300D · #8 03-04-2008, 03:59 PM

I had a 240D that would do that also. On a cold startup it would miss a bit and put out a fair amount of unburned diesel smoke, and maybe some oil smoke. For the most part though I think it was unburned diesel. Running down the road for one mile would clear it up. And sometimes it would do it considerably worse than other times.

The engine had plenty of power and would drive the car quite fast.

I attributed the problem to a sticky injector, or one which would leak down diesel fuel into the cylinder after the car is stopped.

How much mileage do you think you have on your injectors?

Ken300D

Bajaman · #9 03-04-2008, 04:25 PM

Quote:

Originally Posted by airbus

A compression test might provide some insights.

I agree. Low compression will result in a lot of smoke until the engine gets warm enough to fire on the compromised cylinders. Also you could try the injector hard-line loosening trick to see which cylinder is not firing.

1981_300sd · #10 03-04-2008, 04:28 PM

Question about the compression test, what will that show? Not that I doubt you at all, I just wondering why it would work great warmed up but not cold?

Usually when compression is low, isn't it hard to start in the mornings? I can start my car without glowing the plugs, right away even when cold in the morning, of course I do glow the plugs, just saying that it will start right away even without letting the plugs glow.

Bajaman · #11 03-04-2008, 04:55 PM

It's not definite that the compression is low, just a possibility. Low compression will cause rough running and smoke just like you describe. Once the car gets warm, it will fire on the low cylinder simply because everything is warmer. When its cold and smoking, try revving it a little and see if the smoke goes away. Faster compression cycle means less heat loss=more combustion=less smoke.
Doing a purge doesn't outlaw the possibility of filthy injectors either. No miracle treatment is going to replace worn out injector tips. Don't take it personally, just kind of think diesel purge is kind of silly.

barry123400 · #12 03-04-2008, 05:03 PM

Read the milli volts with engine running cold from the glow plugs. Take the injector from the cylinder reading the lowest milli volts before engine totally warms up.
Swap it with its neighbour. If the problem moves with the injector milli volt wise have the injector serviced. Inspect the pre chamber for the incorporated ball still being intact as well. Normally I would do this after a compression check. Since the engine appears to recover nicely and starts easily cold compression is possibly ok.
Quickest way of finding a questionable injector or cylinder and proving it if it is there. Too many people have all their injectors tested without even knowing it is the problem and perhaps only one is bad. Read about the milli volt method in the archives if interested. Post values observed if pursued. Helps many absorb the concept.
That said it still could be a valve seating problem due to carbon etc as suggested or something else of course. I would just want to find the missing cylinder as quickly, cheaply and easily as possible.
It also takes less than a minute to establish the glow plugs are all good..Remove the glow plug harness plug. Read the resistance to ground of all the contacts individually with the engine off. All should be about the same. Around 1 OHM. You of course can read the milli volt output from the glow plugs themselves on that harness plug as well to find your cold or substandard cylinder with the engine running. The cold cylinder will have a very low voltage output from the glow plug in comparison to the normal cylinders.

1981_300sd · #13 03-05-2008, 08:38 AM

Thanks for the replies. Everyone is very helpful and willing to share information, thats why I love this forum

I am not sure how many miles are on the injectors. The car shows just over 150,000 miles, but I dont know if those are true miles. The guy I bought it from said the engine was rebuilt 30,000 miles previous to me buying it but I dont know how honest he was.

He said that his son drove it once without oil or something and thats why it had to be rebuilt. When I did the valve adjustment, the valve cover had some bad scrapes right above the timing chain, so I wonder if it broke at some point.

I have recepts from the guy and saw the info about the rebild but after the car purchase, I noticed it said the wrong year - the guy had another mercedes too that mached the other year. He said the mechanic accidently put the wrong year on the paperwork, so I really dont know how old or new anything is in that car.

So back to the issue, looks like I need to do a compression test and check the injectors.

Unfortunatly my troubleshooting may have to wait a little bit because my tile in my house started to crack last night, and my front door wont close all the way. I think my house shifted, and the tile company wont replace the tile, so I am going to have to do it myself. Between the car and the house, maintenance will never end

vstech · #14 03-05-2008, 10:23 AM

don't forget to recheck your valve clearance.

chasinthesun · #15 03-05-2008, 10:50 AM

TRY REEMING OUT THE GLOW PLUG HOLE ALSO .My 78 300cd would chug a little on start up ,then idle out nice after 3 minutes or so .I never did the reem on the g-plug hole and Im certain if I had it would of helped out the pre-glow for better ignition.Try letting your glow plugs go for 3 cycles before kicking it off,If it sounds like it fires up better then Im betting the carbon build up around the glow plugs are getting pretty bad.