Accumulator (000 476 0621)

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Accumulator
0004760621.JPG
Part number(s) 000 476 0621
000 476 0521
Used on 107
124
126
201

Description

The fuel accumulator maintains the pressure in the fuel system for a certain time after the engine has been switched off. When the engine is running it serves to deaden the noise of the electric fuel pump. After the engine has been switched off, the fuel accumulator maintains the pressure in the fuel system in order to facilitate re-starting, particularly when the engine is hot. The design of the accumulator housing is such that it deadens the noise from the fuel pump when the engine is running. [1]

The interior of the fuel accumulator is divided into two chambers by means of a diaphragm. One chamber serves as the accumulator volume for the fuel, the other chamber contains a spring. During operation the accumulator chamber is filled with fuel. This causes the diaphragm to bend back against the force of the spring until it is halted by the stops in the spring chamber. The diaphragm remains in this position, which corresponds to the maximum accumulator volume, as long as the engine is running. When the engine is shut off the spring chamber holds pressure in the fuel system. When the accumulator fails you may hear excessive pump noise and experience "dirty" hot starts after the engine has sat for 5 to 30 minutes. [2]

Removal / Installation

W124

  1. Exhaust fuel pressure, open the fuel cap
  2. Disconnect battery
  3. Lift vehicle
  4. Remove black protective cover for fuel pump package underneath the vehicle.
    1. Located under rear right side.
    2. 4x 10mm plastic nuts
  5. Pinch off fuel suction hose and pressure hose
  6. Loosen fuel line
    1. 17mm on fuel line, 14mm on accumulator side
  7. Remove leak hose
  8. Remove screws retaining fuel package cage and you should have enough room to snake the fuel accumulator out towards the direction of the 17mm nut
  9. Installation is reverse
    1. Remove pinch pliers from fuel hoses
    2. Check for leaks
    3. Reinstall protective cover


Troubleshooting

If your car is hard to start after it had been recently shut off, then the fuel accumulator may be a source of fuel pressure loss if it is faulty.