Genuine Mercedes-Benz C320 Fuel Pump

Mercedes-Benz C320 Fuel Pump Parts and Q&A

• Fuel Gauge Sending Unit
  203-470-23-94-80
  Q: How to remove and install the fuel level sensor module and fuel pump/fuel level sensor module on Mercedes-Benz C320?

  A:

  First would be to take out the pressure head of the fuel system and make the cable lose contact with the negative battery. Do not empty fuel now, but do not fill up either: it can be fueled low, though it may need to be disconnected to drain submerged fuel hoses or, if it is full up, use a hose on the fuel filler neck to empty the tank. A hard nylon tube with a 30 degree cut is used to push the check valve open in the fuel filler neck, or to siphon the fuel by removal of the retainer ring in the fuel pump/fuel level sensor module. Then detach the bolts to take out the rear seat cushion and the metal access cover. Unplug the electric connector of the fuel level sensor module, remove the special hose clamps, and part with the fuel supply and its return hose. Clean the space around retainer of fuel level sensor module and unscrew it (with special fuel pump retainer tool) or with large water pump pliers (where the tool is not available) taking care not to damage the retainer. Record the four positions of the module before dismounting on top of the tank by placing a corresponding mark on each top-side locating cover, recording the upward arrow on the locating cover, with the position on the tank. To de-align the float arm, remove the fuel level sensor unit, which is customarily the last item to be installed, lifting the electrical connector and the fuel supply and fuel return hose, and manually rock the unit upward on the floating arm. Install O-ring and new sealing ring on a fuel supply hose elbow, and fit the module, keeping the arrow on the locating cover in line with mark taken earlier. In the case of the fuel pump/fuel level sensor module, which is the hardware in the right compartment of the Fuel Tank, repeat the steps above but facing the opposite side; remove metal access cover, clean the area under the retainer, and with the desired tools, unscrew the retainer. Mark module position, detach locating cover and de-hook electrical connector and fuel line. Disconnect the fuel return hose, then lift the module to remove the hose, which you tilt as needed to keep the float arm out of danger. The opposite of removing is the method of installation.
• Fuel Pump
  203-470-10-94
  Q: What is the preliminary check for the fuel pump and how do you perform a pressure check on Mercedes-Benz C320?

  A:

  The fuel pump is contained in the Fuel Tank. To test its operation, with the ignition key in an ON position (not START) listen for low whirring sound which indicates pump working. If the sound is not heard from inside the car, thread off the fuel filler cap and have someone turn the ignition ON while you listen close to the fuel filler. If the pump fails to fire, check the fuel pump fuse and relay in the fuse and relay box on the trunk's left side. If the above components are OK, check the wiring of the fuel pump. If all checks out and pump is running all the time with the ignition in the ON position, then the Powertrain Control Module (PCM) may be defective and should be evaluated by a qualified service department. For fuel pressure test, fuel pressure gauge that can measure high pressure is required and adapter for the Schrader service valve on Fuel Rail. Start by getting the fuel system pressure out. Remove the Schrader valve cap and attach the gauge to fuel rail. Start the engine and check the pressure on the gauge and see if it falls within the specified range. If the pressure is low but below specifications, look for restrictions in the fuel system, such a check the fuel inlet strainer that is located at the base of the fuel pump/fuel level sensor module and cannot be replaced separately. If the pressure is above specifications, then the fuel pressure regulator, an integral part of the Fuel Filter, which is located behind the left chamber of the fuel tank, should be replaced.