Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 10-04-2000, 03:36 PM
Registered User
 
Join Date: Mar 2000
Location: Southampton, NJ
Posts: 126
Yes, this is a elementary question, but I am looking for a concise answer from you Pros.
My '85 300D smokes when I nail it and when I am running down the highway under a load. It is not super excessive, but noticeable. I am wondering if the pump timing is off or something else. All maintenance is up to date and the car runs well, but I also only achieve 23-25 mpg, while others achieve 27 mpg regularly. Any and all ideas are welcome
Thanks.

'85 300DTurbo-175,000 miles
Reply With Quote
  #2  
Old 10-04-2000, 06:58 PM
Registered User
 
Join Date: Aug 1999
Location: ajax, ontario, canada
Posts: 773
a diesel smokes under load because there is not enough oxygen in the intake charge for a perfect stoichiometric air-fuel mix.

under ideal conditions, carbon dioxide (CO2) and water vapor (H2O) should be produced, among other things. If there is not enough oxygen, carbon monoxide (CO) and carbon particulates are produced, among other things. It is the carbon particulates that make up the "smoke", since CO is colorless.

for this reason, diesels are a good candidate for force-fed induction systems.

Reply With Quote
  #3  
Old 10-04-2000, 09:25 PM
mattsuzie
Guest
 
Posts: n/a
CO (carbon monoxide), CO2, and H20 (g) are all colorless.

Your car may be regulated as to ratio of gas/air burned in the cylinder. If there was not even air in the cylinder during acceleration, your cylinder would run "rich" and would you find remninces of poor performance symtoms and fuel economy on both gas and diesel engines and most of the time a smokey tailpipe does not necessarily dictate the above.

I think in my uneducated opinion, black smoke exiting from diesels is a result of "unburnt" oil leaking through the piston rings, hence not fully combusting. Perhaps this happens more often than gas engines because diesels burn at such higher compression ratios than gas engines that the rings give out sooner or the fact that the smoke is coming out of diesels with tons of miles on the engine. It is not uncommon to find diesels with 250,000 + miles on the road daily.

As you can see, smoke does not come out of brand new diesels, it is the ones with lots of mileage. Imagine punching the gas of a brand new diesel and getting that smoke due to lack of air? That would be unacceptable for $50,000.

Just my 2 lire.

------------------
'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)
Reply With Quote
  #4  
Old 10-05-2000, 01:54 AM
JJSMILHOUS
Guest
 
Posts: n/a
I AGREE UNDER A STOICHIOMETRIC FUEL MIXTURE NO SMOKE IN A DIESEL CAN BE ACHIEVED, (THE BIG HOWEVER) DIESEL FUEL IS PRIMARYALY REFINED OIL AND IS CUMBUSTED UNDER HIGH COMPRESION. AS DIFFERERENCS IN ALTITUDE CHANGE, COMPRESSION LOWERS DUE TO WEAR, FUEL INJECTION PUMPS USUALLY BECOME RICHER WITH TIME ETC,ETC, IT BECOME INCREALINGLY DIFFICULT FOR A MOTOR TO BURN ALL OF THE OIL IN DEISEL FUEL. THIS RESULTS IN THAT BLUE TO BLACK SMOKE. OF COARSE IF YOU HAVE REALLY BLACK SMOKE LOOK INTO A TURBO OIL SEAL LEAK WHICH INTRODUCES ENGINE OIL INTO THE EXHAUST SYSTEM,RESULTING IN CLOUDS OF SMOKE!!!!!


RETIRED CATAPILAR,DIETZ DIESEL MECH.
Reply With Quote
  #5  
Old 10-05-2000, 10:32 AM
Member
 
Join Date: Jun 1999
Location: Quezon City, Philippines
Posts: 79
Check your air filter. It could be partially blocked, restricting air supply to your engine.

Also, have your injection pump calibration checked, most especially fuel quantitiy at full load, and performance of air ratio control (LDA).

Often, black smoke is a sign of rich fuel mixture.

------------------
Jake
Reply With Quote
  #6  
Old 10-05-2000, 02:08 PM
fz500sel's Avatar
Happy now in paradise!
 
Join Date: Nov 1999
Location: Venice, FL - "sharktooth capital of the world"
Posts: 712
The smoke is the James Bond smoke screen benefit that all of us older diesel owners enjoy. While on the freeway, there was a convertible Mustang full of young girls that I noticed in my rear view mirror. The driver was weaving in and out wrecklessly. She looked barely old enough to be driving. I watched them and unfortunately for them, they got stuck behind me. I was in my '85 300D and I slowed to about 55-60 mph. Suddenly I floored it and out came the smoke screen. After the smoke cleared somewhat, they went around me and as they passed I could still see them waving their hands back and forth in front of their faces to dissipate some of the smoke. Needless to say, all the other drivers who were annoyed with them were laughing as well as I.

------------------
FrankieZ
84 500SEL EURO 87K
85 300D 267K (and still goin' strong)
Reply With Quote
  #7  
Old 10-05-2000, 04:06 PM
Registered User
 
Join Date: Oct 1999
Location: Culver City, CA, USA
Posts: 62
Going from memory and what I remember from my combustion class.
The strange thing about diesels is that their A/F ratio varies from idle to full load. If you look at what happens: The same amount of air (minus induction efficiency at given RPM) is induced into the cylinder at every intake stroke. The fuel is then injected into the air charge. At idle a small amount of fuel is injected and at full load the maximum amount of fuel is injected. The maximum ammount of fuel is designed based on a "fresh" engine. Once the engine gets "tired" it will flow less air, have a higher leak down rate in the cylinder or have a slightly smaller compression ration due to wear ( not much though). All these factor add up and the engine ends up with less air for a given amount of fuel, assuming the amount of fuel does not change.
As the engine gets older the the cylinder produces a lower pressure. Combustion efficiency is based in part on the air pressure, and thus heat, in the cylinder. As the pressure falls less fuel can be burn completely.
Another factor can be carbon build up in the head or worn injectors. This can cause the fuel to pool up into large droplets. These large droplets will not burn completely in the amount of time that the combusion has to finish.
Again, this is from the top of my head.
Mark.
Reply With Quote
  #8  
Old 10-07-2000, 01:01 AM
Registered User
 
Join Date: Mar 2000
Location: Southampton, NJ
Posts: 126
Thank you all for the articulate responses. I tink I will have the injector pump calibrated when I have the valves done and see if that helps. I do agree that the smoke screen effect is cool at times to thwart off tailgaters. Thanks again.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Anyone who wants to meet and smoke the cruise with a group of MB diesels is welcome whunter Tech Help 0 08-12-2004 12:43 AM
MBZ new diesels article pdxman Diesel Discussion 1 05-25-2004 01:40 PM
New Diesels Dana B. Diesel Discussion 0 08-22-2003 09:11 PM
Lots of smoke from Car...need assistance. Damion Vintage Mercedes 8 04-10-2003 09:14 PM
white smoke from under the hood. emilo Tech Help 8 04-03-2001 04:56 AM



All times are GMT -4. The time now is 10:16 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page