Checking the fuel system, replacing the fuel filter (Mercedes-Benz M-Class W163)

Warning! Gasoline is highly flammable, so special precautions must be taken when working with any components of the fuel system! Do not smoke or approach the work area with an open flame or unprotected portable lamp. Do not carry out such work in garages equipped with heating devices that operate on natural gas (such as water heaters, dryers, etc.)! The work area must be well ventilated. If gasoline gets on your skin, wash it off immediately with soap and water. When doing any work on the fuel system, wear safety glasses and keep a fire extinguisher handy. If gasoline spills, wipe up the puddle immediately, but do not keep gasoline-soaked rags in places where there is a risk of ignition!

System check

1. If you smell gasoline while driving or after the car has been standing in the sun, you must immediately check the condition of the entire fuel system.

2. Remove the fuel tank cap and check it for damage and corrosion. The sealing insert on the cap should be intact. If there is damage or corrosion, replace the cap.

3. Inspect the fuel system inlet and return lines for cracks. Make sure that the connections between the fuel system lines and the fuel injection system, and between the fuel system lines and the built-in fuel filter are not loose.

Caution: On vehicles equipped with a fuel injection system, the system pressure must be relieved before servicing the fuel hoses (see Chapter Relieving pressure in the fuel system of a gasoline engine)!

4. Since some fuel system components - such as the fuel tank and some fuel system lines - are located underneath the vehicle, they are easier to inspect when the vehicle is jacked up. If this is not possible, jack up the vehicle and support it on jack stands.

5. With the vehicle raised, inspect the fuel tank and filler neck for holes, cracks, or other damage. Pay particular attention to the condition of the connection between the filler neck and the tank. Sometimes fuel leaks occur due to loose rubber neck clamps or damage to the neck material. Inspect all fuel tank mounting brackets and straps to ensure that the tank is securely fastened to the vehicle.

Warning! Never, under any circumstances, attempt to repair the fuel tank (excluding the replacement of its rubber components). A welding flame or any other open flame can easily cause the gasoline vapor inside the tank to explode.

6. Carefully inspect all fuel hoses and metal lines coming from the tank for loose connections, twists, signs of wear on hose materials, and other damage. Repair or replace damaged sections as necessary.

Filter replacement

Petrol models

1. Details of the fuel filter installation on petrol models are shown in the illustration.

2. Open the fuel tank cap to equalize the pressure in it with the atmospheric pressure.

3. Remove the left rear wheel.

4. Remove the wheel arch protection liner.

5. Disconnect the pressure (90/12) and return (90/11) lines from the fuel filter assembly - squeeze the locking tabs on both sides of the lock, try not to allow the tubes to twist.

6. Disconnect the spring chamber breather tube (77/3).

7. Loosen the retaining clamp (91/1) and remove the fuel filter assembly with the pressure regulator connected to its front part.

8. Assess the condition of the mounting clamp and replace it if necessary.

9. Installation is carried out in the reverse order. Tighten the fuel filter mounting clamp with a force of 3 Nm.

10. Start the engine and check the relevant fuel system components for signs of developing leaks, tighten the fastening clamps/connectors if necessary.

Diesel models

Details of the fuel filter installation on diesel models are shown in the illustrations.

Removal air from the fuel system of a diesel engine

If the engine has stopped due to the fuel tank being completely empty, then after refueling it is necessary to remove air from the fuel system. To do this, start the engine continuously for no more than 60 seconds until it starts to run steadily.