Note: Before you begin, read the safety precautions in Section Safety precautions and rules for maintaining cleanliness when working with the fuel system
Caution! Following the procedure below will only relieve excess pressure from the fuel system. Gasoline will remain in the lines. Take all necessary precautions before disconnecting any fuel hose.
The fuel system considered in this Chapter consists of a fuel tank, a fuel pump located inside it with a fuel gauge, a fuel filter, injectors, a pressure regulator and various hoses and tubes. Inside all these units during engine operation (and also with the ignition on) the fuel is under pressure.
After the ignition is turned off, the pressure in the system remains for quite a long time. Before disconnecting any of the above components, the pressure must be released.
The simplest way to relieve pressure is the following. Remove the fuel pump fuse and start the engine. If the engine does not start, crank it with the starter for a few seconds, and if it does start, wait until it stops on its own. In order to completely relieve pressure, crank the engine crankshaft with the starter a couple more turns. Turn off the ignition and replace the pump fuse.
The pressure relief valve located on the fuel distribution line works on the principle of a simple nipple. Place a rag around the valve, remove the cap and press on the nipple. After completing the work, do not forget to put the cap back in place.
Please note that if the pressure is released (or fuel has been removed from the system), the engine will take longer than usual to start. You will have to crank the engine with the starter for at least a few seconds, during which the pressure in the system will be restored and the fuel will fill all the lines.
[Material based on data from the portal: MercedesMAN]