'79 450 SL - Vapor Lock or Fuel Accumulator ?

[Max J. Sandler]

On the 86 560 SL there is a rubber shield just behind the rear axle on the passenger side of the car. Behind the cover are the two fuel pumps, each with an integral check valve. The fuel filter is located directly above the pumps, and the accumulator is located directly behind that. Each of the fuel pumps has a check valve on the output side which can be a potential source of the problem as well as the accumulator. The check valves can be unscrewed and replaced without removing the pumps. With regard to the question of where it to get the accumulator or the check valves, FastLane stocks these parts. Before you do anything, do a pressure test of the system to confirm that pressure is "bleeding down" after the engine is turned off. If that is the case, you can proceed as follows:

1. Raise up the rear of the car to gain access. Jack stands are good if on a hard, flat surface, ramps are better.

2. DISCONNECT THE BATTERY! Pinch off the life from the tank before you start, unless you like bathing in gasoline.

3. When you initially open a fitting, wrap a rag around it because the system is pressurized.

4. Whatever components get replaced, also replace the fuel filter. The system is extremely sensitive to dirt.

5. The pumps, filter and accumulator are in clamps which are mounted on rubber mounts with four nuts. It's a lot easier to undo these nuts and drop the whole assembly than to mess with the clamps holding the individual components.

6. When disconnecting fitting from any of the components, note that there hex flats that allow you to hold it still while breaking the fitting loose. If you don't do this, you can damage both the component and/or the fuel line.

This is medium-range DIY project which you should be able to complete in less than two hours.

[PCM84]

from Fastlane