White smoke at idle - PeachParts Mercedes-Benz Forum

eatont9999 · #1 03-29-2013, 03:30 PM

All,

I have been noticing white smoke at idle for a while now on my 300SD. The smoke smells fuel rich and I am almost certain it is related to injection timing. Before I start assuming anything, I will be doing the following:

Valve adjustment
Compression test
Check cam timing by lining up the marks
Pop test injectors
Check compressor shaft play

Injectors were rebuilt less than a year ago with new Monark nozzles. All pop tested and balanced. Valves were adjusted about a year ago. Car has been running on straight D2 for over a month.

Should I do a wet test when I check the compression? I presume as usual, the engine should be warm during the test.

I need to look into drip timing, etc. the IP if I do not see an obvious problem with the above tests.

Any suggestions or advice is appreciated.

cho · #2 03-29-2013, 04:21 PM

.

could be injection timing,some slack in chain,but aligning marks is not
the ultimate test. to be sure you have to go 2mm dial gauge.

engine has to be 30C for compression test .....

edit: often cause of white smoke is inadequate heat also
do you have white smoke idling on start only or..... ?

.

eatont9999 · #3 03-29-2013, 05:25 PM

Quote:

Originally Posted by cho

.

could be injection timing,some slack in chain,but aligning marks is not
the ultimate test. to be sure you have to go 2mm dial gauge.

engine has to be 30C for compression test .....

edit: often cause of white smoke is inadequate heat also
do you have white smoke idling on start only or..... ?

.

I know the dial gauge method is the most accurate way. What I am looking for is a major offset from factory spec; something that would be able to cause the problems I am seeing.

The smoke exists more when cold but still visible and smells the same at operating temp. The car usually reaches max operating temp at 90C or the next mark up from the 80C designation. I also see a little more crank time to start the engine during cold weather.

Given my experience with other Diesel engines, I am about 95% sure that my issue is caused by injection timing retardation. All the symptoms add up. None the less, I am going to eliminate all other possibilities first before I start messing with IP adjustments.

Diesel911 · #4 03-29-2013, 08:15 PM

Like Cho said; late Fuel Injection Timing will cause white smoke; the other thing is a coolant leak.

However, you said there was a Fuel smell to it.
When I re-installed the IP on My Volvo Diesel many years back I had billowy white clouds coming from the Exhaust that smelled like Fuel.
I did some reading and found that white colore is caused by unburned atomized Fuel.

When the timing was corrected the white smoke went away.

You can get some idea concerning your Camshaft Timing as effected by Timing Chain Stretch and Timing Gear wear by lining up the Timing mark behind the Camshft Gear exactly with the Timing Mark on the Front Camshaft Bearing Tower and looking down at the Crankshaft Damper degrees the Pointer points to.
If the is significently off do the 2mm Method and then you can decide if you want to use an offset Key to bring the Camshaf Timing back to spec.

The Timing Chain strech issue throws the IP Timing off but because it is driven by the same Chain. However, when you time the IP you are timing it to the Crankshaft degrees so if you re-do the IP timing that is OK.
I am not sure but I don't think changing to an offset Woodruff Key will restore your IP Timing; I think it only restores the Camshaft Timing.

Left Coast · #5 03-29-2013, 08:39 PM

Could be a problem with injectors, despite the fact that they were recently re-done. That's where I would start.
While you have them out, you have a good opportunity to check compression.

eatont9999 · #6 03-29-2013, 09:32 PM

Quote:

Originally Posted by Diesel911

Like Cho said; late Fuel Injection Timing will cause white smoke; the other thing is a coolant leak.

However, you said there was a Fuel smell to it.
When I re-installed the IP on My Volvo Diesel many years back I had billowy white clouds coming from the Exhaust that smelled like Fuel.
I did some reading and found that white colore is caused by unburned atomized Fuel.

When the timing was corrected the white smoke went away.

You can get some idea concerning your Camshaft Timing as effected by Timing Chain Stretch and Timing Gear wear by lining up the Timing mark behind the Camshft Gear exactly with the Timing Mark on the Front Camshaft Bearing Tower and looking down at the Crankshaft Damper degrees the Pointer points to.
If the is significently off do the 2mm Method and then you can decide if you want to use an offset Key to bring the Camshaf Timing back to spec.

The Timing Chain strech issue throws the IP Timing off but because it is driven by the same Chain. However, when you time the IP you are timing it to the Crankshaft degrees so if you re-do the IP timing that is OK.
I am not sure but I don't think changing to an offset Woodruff Key will restore your IP Timing; I think it only restores the Camshaft Timing.

Everything you said is correct. I believe the key adjustment only affects valve timing. I still wanted to rule out low compression due to a valve not closing completely, so that is why I tested the cam timing. IP timing is done via drip method or I believe there is a sort of lock that sets the timing on the pump, then you cant the pump or something like that.

All but turbo shaft play has been tested and recorded. Descriptions and images to follow soon.

eatont9999 · #7 03-29-2013, 09:42 PM

Preliminary results:

Valves were a little tight; as to be expected. Adjusted to spec.
Compression test reveals the following:
1: 350
2: 350
3: 320
4: 320
5: 350
I sprayed a few squirts of PB Blaster in each prechamber to help break up the carbon deposits before testing the compression. I cranked the engine with the injectors removed before testing compression. A dry or wet test result is up to the reader based on my method. I did not put any oil into the cylinder/prechamber, though. An oil change will be required soon to be sure no adverse effect of the PB Blaster is seen if it has entered the crankcase oil.

Cam timing pictures will be posted soon.

Injectors pop tested well and in MB spec for new injectors. 1850PSI to 1875PSI great spray pattern, no leaks. Chatter like a chipmunk.

eatont9999 · #8 03-29-2013, 10:20 PM

Index of /images/83mercedes-benz300sd/timing-check

eatont9999 · #9 03-29-2013, 10:22 PM

eatont9999 · #10 03-29-2013, 10:24 PM

eatont9999 · #11 03-29-2013, 10:28 PM

Number 3 was the only injector with a heat shield that was not coked with carbon. I don't understand that.

Power is the same as it was before. As for smoking, I need to check tomorrow. I gave her an Italian job after all the work was done. Exhaust smelled pretty normal, maybe a tad rich, afterwards.

Diesel911 · #12 03-30-2013, 12:39 AM

Quote:

Originally Posted by eatont9999

Everything you said is correct. I believe the key adjustment only affects valve timing. I still wanted to rule out low compression due to a valve not closing completely, so that is why I tested the cam timing. IP timing is done via drip method or I believe there is a sort of lock that sets the timing on the pump, then you cant the pump or something like that.

All but turbo shaft play has been tested and recorded. Descriptions and images to follow soon.

With the Drip Timing Method there is no locking Tool Used.

I am not sure your Year has the port in the side of the Governor for the Timing/Locking Pin.
In the Pic if you have a 17MM Plug where the Blue Arrow Points you have a port for the Locking Tool. The Red Arrows Point to the 2 screws that hold a separate Plate thet the Plug Screws into.
On the Older Model Pumps that cannot use that Timing Locking Pin there is no Separate Plate and there is a smaller Plug directly screwed into the Governor Housing Casting.

No matter what timing method you use put a mark acrossed the Block and the Fuel Injection Pump Mounting Flange so you can return the Pump to the original positon if you are having problems.

barry12345 · #13 03-30-2013, 12:11 PM

I would milli volt those glow plugs because of the appearance of the third injector. To me it looks like that element may be very late perhaps. Do you remember if the third cylinder had the tightest valves? If so and the additional fueleing odour is gone with the timing adjustment etc. I would forget it.

Others may interpret the third injector differantly but something was going on in that cylinder I suspect.

97 SL320 · #14 03-30-2013, 01:10 PM

I'd say that post 46 in the attached thread has a lot to do with the carbon build up in a years time.

If I wanted to dump some used motor oil in my fuel tank,,,,,,,,,

Poor atomization has a lot to do with smoke at idle.

Diesel911 · #15 03-30-2013, 03:11 PM

If he had a bad Injector or Fuel Pump Element you would think it would effect the Performance when the Car is moving, the Engine smoothness at Idle speed, and if it was causing the white smoke at idle the smoke would puff out unevenly white.