Checking the ignition timing on petrol models
1. The corresponding illustrative material is presented in the illustration Setting the basic position of the camshafts of gasoline engines M112/113 and the illustrations above, to which all references in the text refer.
2. Remove the cylinder head covers (see illustration Installation details of cylinder head covers on M112/113 petrol engines (using the M112 as an example)).
3. On models equipped with an air pump, loosen the combination valve (right head), - the valve sealing gasket must be replaced without fail.
4. Check that the ignition timing angle is set correctly (see Specifications).
5. Rotate the engine to the position 40° after TDC of the piston of the first cylinder (see Section Checking and adjusting the basic position of the camshafts).
[Original can be found on the website: MercedesMan]
6. Check the basic position of the camshafts (see Section Checking and adjusting the basic position of the camshafts).
7. On models equipped with the M112 engine, check the basic position of the balance shaft (see Section Checking the basic position of the balance shaft (only engines M112 and 628)).
8. Installation is carried out in reverse order.