Engine going south??? - Page 2 - PeachParts Mercedes-Benz Forum

kerry · #16 08-20-2004, 09:29 PM

A picture is worth a thousand words. My vote goes with unburned diesel fuel. When my Austin Healey was burning oil sucked directly into the intake manifold, the smoke was much whiter and more of it.
I don't know if it is a bad IP, timing off, or some other problem but I think it's a fuel related problem of some kind, not a compression problem.

psfred · #17 08-20-2004, 09:35 PM

I would pull the injectors and have them checked, I would guess one or more have failed. A compression test wouldn't be amiss, either -- very low compression will give lots of white smoke cold (and black smoke hot!) along with low pwoer, but if you have ormal power, compression is probably OK

A nozzle stuck open will deliver fuel at low pressure too early, so it fails to burn very well making smoke. Stuck shut and only opening intermittantly wii also make smoke from late injection (also no burn).

Are you using/gaining on oil?

Peter

JimmyL · #18 08-20-2004, 09:45 PM

The oil consumption hasn't really changed since I got the car in May, 4500 miles or so. Needs to be topped off every week or so, but not a large amount. This non-turbo never has had any power. Should I remove and clean the injectors or try diesel purge, or both? With the drop in fuel mileage and the thick diesel smell, it does sound injector/IP related I guess. Right?
JL

whunter · #19 08-20-2004, 10:13 PM

Go back and adjust the valves again.

This time adjust them loose, meaning sloppy on the feeler gauge.
It is amazing, how many gasser mechanics can not adjust diesel valves correctly.

Diesels like a slightly sloppy adjustment.

Remember this is not a top fuel drag engine, where the feeler gauge can just manage to force its way in.

I would rather go loose than tight; tight can under the wrong circumstances cost you a set of valves.

Note:
Too tight = not fully sealing and spewing unburnt fuel = white smoke.
Too loose = not opening far enough or long enough = weak power.

Try again; you will get it dialed in this time.

Quote:

Originally Posted by JimmyL

Just posting example pics of the smoke. The hose from valve cover to air cleaner is not attached at this time. No real noises out of the ordinary except for the sputtering and coughing and missing. No loud knocks in other words. I would welcome ideas on how to procede at this point. Reminder, the fuel milage has steadily gone down from 22-23 to just over 17 on the last tank, if that is helpful. Heavy smell of diesel, and the cloud lingers for quite a while.
Jimmy

pberku · #20 08-20-2004, 10:18 PM

Try this simple test.

Remove the Radiator/Overflow-tank cap and see if it now emits noticeably less white smoke.

The theory being that if the cooling system is not pressurized, and the problem is indeed the head gasket, or a cracked block, then with no pressure, there should be less coolant entering the combustion chambers, resulting in less white smoke.

If the amount of white smoke, after removing the cap is unchanged, then you need to look elsewhere. (Which could be good news, I suppose)

Phil

JimmyL · #21 08-20-2004, 10:54 PM

whunter,
I WILL go back and adjust the valves again. I did not leave them 'sloppy' for sure. I adjusted them per Haynes, which said to have drag on feeler gauge. I probably won't get to this until Sunday at the earliest, but it is an easy step, and I'm getting good at removing everything. Fan has to come off to make turning over motor easier, but I've got it down at this point.

pberku,
I appreciate your advise too. It really doesn't seem like that kind of smoke, especially with the choking smell of diesel being so strong, but if valve adjustment fails I will surely test your theory.

I'm appreciative for the effort. My little photographer will be happy too if we get 'The Flash' going again.

Jimmy

JimmyL · #22 08-22-2004, 10:55 PM

Went back and adjusted valves. Again. I made them all a loose .1 or .3. Loose defined as very sloppy with said correct gauge, but a .15 or a .35 won't penetrate. Still smokes and won't idle. Exactly the same.
I tried to take a picture of the timing mark (chain stretch indicator), but that area would not illuminate enough to see anything. With the marks lined up correctly (TDC), I can't really tell what the stretch mark position is(fight through my terminology please). People occasionally attach a picture or drawing of it, but it has a pin sticking out over guide marks, and mine doesn't have a pin like that. Now their attachment is for a different motor, but for the life of me, on mine there is a very confusing set-up. You may get a chuckle out of my stick figure-type drawing, but it gives the idea of what it looks like. It appears I could either have 0 stretch, 15 stretch, or other....
Is this hardware/mark indicator correct?
Still undrivable. How would yall recommend I procede?
Appreciative,
Jimmy

psfred · #23 08-22-2004, 11:54 PM

It's possible the pointer is missing, it's a sheet metal tab stickout out from the block over the balancer on the front of the crank.

Chances are it's only filthy. Look down right beside the right (passenger) side of the fuel filter, it should be easily visible, if a bit hard to get to. Some carb cleaner or brake parts cleaner spray will flush enough oily dirt off to get a good look at it.

The mark on the cam is a bit harder to see -- it's a bump on the cam tower at about 2 o'clock, the bit you align is the notch in the thrust washer that rotates with the cam. You have to be pretty carefull to get the notch to bracket the bump on the tower, it's a bit wider.

With a new chain, you should be right at 0 TDC on the crank pulley when the notch on the washer is centered. The older the chain, the further behind the crank will be -- mine was something like 13 degrees!

one thing to note -- the IP can still be quite a bit out even if there is little chain stretch.

Peter

FrankM · #24 08-23-2004, 07:38 AM

Fuel restrictions would cause this..

I would assume your fuel filters are ok...

JimmyL · #25 08-23-2004, 08:57 AM

Both have been replaced, fuel tank screen removed. It was spotless and didn't need cleaning. Will clogged injectors cause this? Do I need to try diesel purge, or would this simply be a waste of money based on my symptoms?
I will also do a search on cleaning injectors. Can a DIY'er handle that? And would it help, also based on my symptoms?
JL

whunter · #26 08-23-2004, 08:57 AM

Reverse the fuel hoses going to the fuel tank, only to test, run for thirty minutes, if it cleans up the issue is a plugged tank strainer.

Remove the injectors and check spray pattern + pop test.

Carefully inspect the prechambers while the injectors are out, damage or fouling could do this.

Have a great day.

Brian Carlton · #27 08-23-2004, 09:43 AM

Quote:

Originally Posted by whunter

Go back and adjust the valves again.

Roy, when 617 is run for 25K or 30K miles without a valve adjustment, the valves will typically tighten up, correct?

In fact, it is likely that the valves may be .003 tight after this time period, correct?

It is also likely that the engine will not exhibit any additional smoke when running with the valves .003 tight. It certainly will not exhibit anywhere near what would be described as "heavy white smoke".

So, unless this fellow has adjusted his valves at least .005 too tight, or more, the smoke level cannot be attributed to valves, correct?

whunter · #28 08-23-2004, 01:44 PM

Quote:

Originally Posted by Brian Carlton

Roy, when 617 is run for 25K or 30K miles without a valve adjustment, the valves will typically tighten up, correct?
In fact, it is likely that the valves may be .003 tight after this time period, correct?
It is also likely that the engine will not exhibit any additional smoke when running with the valves .003 tight. It certainly will not exhibit anywhere near what would be described as "heavy white smoke".
So, unless this fellow has adjusted his valves at least .005 too tight, or more, the smoke level cannot be attributed to valves, correct?

Mechanical law of physics, the valve lash will tighten, the longer you drive it without adjustment.

Need much more data.
A small leak on all of these at once is possible.
Rings leaking, valve stems leaking, injectors leaking, over tight valve lash = "heavy white smoke".

Variable results:
Line up six people who know how to adjust gas engine valves, add one good diesel mechanic.
Have each of them adjust OM6 valves cold, drive it five miles, wait twenty four hours and bring in another professional diesel mechanic to check the lash on every single valve.

Odds are; John Doe Public will set four of ten valves too tight on their first and possibly all valve adjustments, I have seen .006 too .001 in real world.

The professional diesel mechanic will set them loose enough to wear in a good seat, you may find his set between .001 and .002 loose, this will affect short term performance only, cracking the glaze on valve and seat allows slight settling for a very good work in seat.

Remember:
All the engines we are talking about are OLD, any or all of them can have carbon layers on the piston or valve.

Four years ago, I opened up an OM6 and found 3 mm of carbon layers on the piston, every valve in the head was bent, and the owner adjusted them tight, every 3000 miles, and thought that was a good thing.

Any tight valve adjustment on a diesel is BAD.

A tight valve adjustment can only get tighter on a diesel.

A bad head gasket or cracked head will also give It what would be described as "heavy white smoke".

Brian Carlton · #29 08-23-2004, 02:05 PM

Thanks for the info, Roy.

BTW, what would cause such variable results? What part of the process in setting the valves using the feeler gauge is variable? It seems to me that you set the valve, tighten the nuts, and check your results with a feeler gauge. The feeler gauge either goes in between the cam lobe or it does not.

Please comment on the variables of this operation and how John Q Public, or a gasoline mechanic for that matter, can get a valve adjusted .005 too tight.
I don't see the variables, myself.

whunter · #30 08-23-2004, 02:13 PM

Off to the doctor for me.