Mercedes-Benz has been making durable and economical diesel engines since the 1930s. There are many differences between diesel engines and their gasoline counterparts, most notably the fuel system. Air can enter a diesel engine's fuel system 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, owners of Mercedes-Benz diesel engines should know how to bleed air from this system.
Open the bonnet and locate the hand operated prime pump. It's on the primary pump on the right-hand side of the engine bay.
Unscrew the handle of the pump by hand in a counterclockwise motion.
Work the pump handle up and down until you feel a resistance and you can hear air escaping from the injection pump.
Push the pump handle back into the pump and twist it in a clockwise motion. Do not over-tighten the pump handle.
Crank the starter to expel any remaining air in the fuel system. Do not crank the starter for more than 30 seconds at a time to keep from damaging the starter. Wait for the starter to cool before resuming cranking.
Follow the subsequent steps if the engine will still not start after several attempts at cranking the engine.
Loosen the attaching nuts of the fuel injectors on the cylinder head with a 17mm combination wrench in a counterclockwise motion. Do not remove the nuts.
Crank the engine until fuel seeps out of the loosened fuel injector nuts.
Retighten the fuel injector nuts with a 17mm combination wrench in a clockwise motion.
Start the engine and allow it to run a few minutes so that any remaining traces of air are expelled from the fuel system.
After bleeding air from the fuel system, your Mercedes diesel may run roughly and there may be excessive smoke from the tailpipe until any remaining air in the system is expelled.
Tips and warnings
- After bleeding air from the fuel system, your Mercedes diesel may run roughly and there may be excessive smoke from the tailpipe until any remaining air in the system is expelled.