Spark Plug Indexing For Direct Injection Engines (6/19/14)
Publication date: 2014-06-19Reference number: 6/19/14
SPARK PLUG INDEXING FOR DIRECT INJECTION ENGINES
QEC / ES TECHNICAL UPDATE
Reference Number(s): 6/19/14, Date of Issue:
June 19, 2014
| MERCEDES-BENZ: | Models With Direct Injection Engine |
SPARK PLUG INDEXING FOR DIRECT INJECTION ENGINES
With direct injection system for engines 157, 276, 278 (for example) the spark plug indexing is very critical as indicated in the picture and the warning information in WIS when replacing spark plugs.
In the picture, an NGK unapproved spark plug is compared to a Mercedes approved spark plug. The NGK plug does not have the correct thread length for proper indexing and it isn't the correct heat range.
Below shows the indexing of the MB plug and the NGK plug when torqued at 23 Nm.
NOTE:
For our direct injection engines, the indexing is up to 45 degrees of either side of the injector center.
In this case, the incorrect spark plug caused major engine damage (melted piston) that lead to a complete engine replacement. This is not a warrantable defect.