by Thomas West
Mercedes-Benz has been making durable and economical diesel engines since the 1930s. There are many differences between diesel engines and their gasoline counterparts, especially the fuel system. Air can enter the fuel system of a diesel engine after a routine fuel filter change. Air will also enter the fuel system if the vehicle has been allowed to run out of fuel. However, air that has entered the fuel system can prevent the vehicle from starting. For this reason, Mercedes-Benz diesel engine owners should know how to bleed air from this system.
Open the hood and locate the hand priming pump. It’s in the main pump on the right side of the engine compartment.
Unscrew the pump handle by hand in a counterclockwise motion.
Move the pump handle up and down until you feel resistance and can hear air escaping from the injection pump.
Push the pump handle back onto the pump and turn it clockwise. Do not overtighten the pump handle.
Crank the starter motor to expel the remaining air in the fuel system. Do not crank the starter motor for more than 30 seconds at a time to avoid damaging the starter motor. Wait for the starter motor to cool down before resuming cranking.
Follow the steps below if the engine still does not start after several attempts to start the engine.
Loosen the lock nuts for the fuel injectors on the cylinder head with a 17mm combination wrench in a counterclockwise motion. Do not remove the walnuts.
Crank the engine until fuel seeps through the loosened fuel injector nuts.
Retighten the fuel injector nuts with a 17mm combination wrench in a clockwise direction.
Start the engine and let it run for a few minutes so that any remaining air is expelled from the fuel system.
- After bleeding the air from the fuel system, your Mercedes diesel may run rough and there may be excessive smoke from the exhaust pipe until the remaining air in the system is expelled.