Fuel Level Sensor

Replace the fuel level sensor located in the fuel tank by accessing it through the rear seat or trunk area service opening, requiring fuel system depressurization and tank access.

Warnings

Tools required

Parts

• Fuel level sensor × 1 — A2214700094 or equivalent
• Fuel pump module seal/gasket × 1 — Use OEM specification
• Fuel line O-rings × 4 — Use OEM specification

Preparation

1. Ensure fuel tank is less than 1/4 full for safety and ease of access
2. Park vehicle on level surface in well-ventilated area away from ignition sources
3. Disconnect negative battery terminal and wait 10 minutes for system discharge
4. Allow engine to cool completely if recently operated
5. Gather all tools and replacement parts before beginning

Procedure

1. 1

   Depressurize fuel system
   Locate the fuel pump relay (relay module in rear trunk area, relay F87/1). Remove the fuel pump relay. Reconnect battery temporarily and attempt to start engine. Engine will run briefly then stall as fuel pressure drops. Crank engine 2-3 more times to ensure complete depressurization. Disconnect battery negative terminal again.
   ⚠️Keep fire extinguisher accessible during this step as engine will be running with exposed fuel system components.
2. 2

   Access fuel tank service opening
   Fold down rear seat bottom cushion by releasing clips at front edge. Remove rear seat backrest by releasing lower mounting bolts. Locate carpeted access panel in floor behind rear seats. Some models have access through trunk floor - remove trunk carpet and locate rectangular access cover. Use trim tools to carefully release clips securing access cover.
3. 3

   Remove fuel tank service cover
   Remove screws securing the metal or plastic fuel tank service cover plate. On this model, there are typically 6-8 cover screws arranged around perimeter. Carefully lift cover to expose fuel pump module assembly. Note the orientation of the cover for reinstallation.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)
4. 4

   Disconnect fuel level sensor electrical connector
   Locate the fuel level sensor electrical connector on top of the fuel pump module assembly. Press the locking tab and carefully disconnect the connector. Clean any dirt or debris from around the connection area to prevent contamination entering tank.
   ⚠Do not allow dirt or debris to fall into fuel tank opening as this can damage fuel system components.
5. 5

   Disconnect fuel supply and return lines
   Using appropriate fuel line disconnect tools, disconnect the fuel supply line and return line from the fuel pump module. The S65 AMG uses quick-connect fittings. Have shop towels ready to catch residual fuel. Cap or plug open lines to prevent contamination. Note the routing and position of each line for reassembly.
   ⚠Expect approximately 50-100ml of fuel spillage from lines. Have fuel-safe container and absorbent materials ready.
6. 6

   Remove fuel pump module locking ring
   Using the locking ring spanner tool, rotate the large locking ring counterclockwise to release it from the fuel tank. The locking ring has multiple tabs - ensure tool is properly engaged before applying force. Once loosened, carefully lift and remove the locking ring.
   ℹ️Mark the orientation of the fuel pump module relative to tank before removal for correct reinstallation alignment.
7. 7

   Remove fuel pump module assembly
   Carefully lift the fuel pump module assembly from the fuel tank at an angle to avoid damaging the fuel level sensor float arm. The assembly will have residual fuel - tilt it to drain back into tank, then place in fuel-safe container. Inspect and remove the rubber seal/gasket from tank opening.
8. 8

   Remove fuel level sensor from module
   With fuel pump module assembly on clean work surface, locate the fuel level sensor attached to the side of the module. On the M275 engine S65 AMG, the sensor is typically secured with 2-3 small mounting screws or clips. Disconnect the internal wiring harness connector. Remove mounting fasteners and carefully slide sensor with float arm assembly out of module housing.
9. 9

   Install new fuel level sensor
   Compare new sensor with old unit to verify correct replacement. Install new fuel level sensor into module housing, ensuring float arm moves freely through full range of motion without binding. Secure with mounting fasteners. Connect internal wiring harness connector ensuring it clicks into place. Verify sensor resistance readings if test equipment available (typically 5-180 ohms across range).
10. 10

    Reinstall fuel pump module assembly
    Install new rubber seal/gasket onto fuel tank opening, ensuring it seats properly in groove. Carefully lower fuel pump module assembly into tank at an angle to protect float arm, then rotate to proper orientation using alignment marks made during removal. Ensure module seats fully against seal.
    ⚠Do not force module into tank. Float arm and sensor must pass through opening without interference.
11. 11

    Install and torque locking ring
    Position locking ring over fuel pump module and engage threads. Using locking ring spanner, rotate clockwise until snug, then torque to proper specification per Mercedes procedure (hand-tight plus 1/4 turn, or approximately 40-50 Nm if torque specification available). Ensure ring is fully seated and locked.
12. 12

    Reconnect fuel lines
    Install new O-rings on fuel line fittings - lubricate lightly with clean fuel. Reconnect fuel supply and return lines to pump module, ensuring quick-connect fittings click securely into place. Tug gently on each line to verify proper engagement. Install any retaining clips.
    Torque spec

    Fuel Line Fittings25 Nm (18 lb-ft)
13. 13

    Reconnect electrical connector and test
    Reconnect fuel level sensor electrical connector to module until it clicks. Reconnect vehicle battery negative terminal. Reinstall fuel pump relay. Turn ignition to ON position (do not start) to activate fuel pump and pressurize system. Inspect all connections for leaks. Cycle ignition off and on 3-4 times to fully pressurize system and check for any fuel seepage.
    ⚠️Carefully inspect all fuel connections for leaks during initial pressurization. Any fuel leak must be corrected immediately before starting engine.
14. 14

    Reinstall access covers and interior components
    Once leak test is successful, reinstall fuel tank service cover plate with cover screws torqued to specification. Reinstall access panel or trunk carpet. Reinstall rear seat backrest mounting bolts and rear seat cushion. Ensure all trim pieces are properly secured.
    Torque spec

    Cover Screws15 Nm (11 lb-ft)

Reassembly

1. Ensure all fuel line connections are secure and properly locked before pressurizing system
2. Verify fuel level sensor electrical connector is fully engaged with audible click
3. Double-check locking ring is properly torqued and seated to prevent fuel leaks
4. Replace any damaged trim clips or fasteners during interior reassembly

Verification

• Turn ignition to ON position and verify fuel pump activates for 2-3 seconds without unusual noise
• Start engine and verify it runs normally without fuel delivery issues or fault codes
• Check instrument cluster fuel gauge - it should display current fuel level accurately (compare to known tank level)
• Use Mercedes STAR diagnostic system to verify fuel level sensor readings match expected values (0-100% range)
• Perform test drive and monitor fuel gauge for accurate level indication during vehicle operation
• Inspect fuel tank access area and all connections for any signs of fuel leakage
• Clear any stored fault codes and verify no new fuel system codes are present after test drive

Related trouble codes on this vehicle

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