The Mercedes-Benz OM604 is a 2.0 litres (1,997 cc) and 2.2 litres (2,155 cc) inline-four cylinder (R4/I4) double overhead camshaft (DOHC) diesel engine with indirect injection manufactured by Mercedes-Benz between 1993 and 1998.
Unlike other Mercedes Benz diesels at the time that used a Bosch inline injection pump the OM604 used the Lucas electronically controlled rotary distributor injection pump (EVE) which is less reliable.
The head is a DOHC design with 4 valves x cylinder and split intake ports.
As per the OM601 it has hydraulic bucket type lifters, thus requiring no periodical valve adjustment It has a double row timing chain that drives the injection pump and the camshafts, the sprocket is on the exhaust camshaft and both cams are connected by a gear drive, while the oil pump is driven by a separate single row chain The Korean company Ssangyong has developed D20DT (created under license from Mercedes) series diesel engines based on the OM604 engine.
Compared to the original Mercedes diesel, the Korean uses the Common Rail fuel injection system, turbocharging (unlike N/A OM604) and has slightly increased the engine capacity to 1,998 cc, compared to 1,997 cc in the OM604.