Hi All,

85 230E with an M102 from an early model 190E 2.3

Healthy, normal quiet engine with ample oil changes and correct oil level.

About two months ago the fuel pump began failing causing the vehicle to starve of fuel when climbing hills. Car was limped home over the corse of an hour or about 40 miles.

Replaced the fuel pump and all other items in the back of the vehicle last night and went to start it up. Fired right up but immediately the engine began making a VERY loud tapping / knocking sound at idle and when revving.

Once the engine warmed up a little the sound diminished at idle but comes back when revving.

I pulled each of the spark plugs one at a time and the sound does not change.

I tried loading the engine (lugging it) while driving and it does not change.

Could this be a noisy valve system component or something worse?
Prior to the fuel pump issue this engine ran very quiet and nearly flawless.

Link to video : https://www.youtube.com/watch?v=pFvz_o4NlvM

I would remove the valve cover start it and observe the valve operation..