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Pelican Technical Article:

Replacing the Fuel Suction Dampener

Mike Holloway

Time:

1 hour1 hr

Tab:

$10 to $40

Talent:

*

Tools:

8mm, 10mm, and 13mm socket wrench with 6-inch extension, 8mm, 17mm open end wrench, flat face and Phillips head screw driver, jack and jack stands

Applicable Models:

Mercedes-Benz 450SL (1975-80)

Parts Required:

Fuel suction dampener

Hot Tip:

Clamp fuel line

Performance Gain:

Proper engine operation

Complementary Modification:

Replace fuel filter

The fuel suction dampener's job is to take out any pulsations of the fuel flow prior to being pumped to the combustion chamber. If you are experiencing erratic acceleration it may be due to fuel pulsations. The dampener may have been damaged, corroded or failed in some other manner. The fuel suction dampener is also known as the fuel compensation valve.

Potential for fire is always a concern when working on fuel systems. Disconnect the battery's negative cable to minimize possibilities of sparks. Consult our article on removing the battery, if you have any questions on how to do this safely. Work in a well-ventilated area away from open flame. Let the car cool down before beginning. Fully heated catalytic converters can ignite fuel vapors.

Always keep a Class B fire extinguisher within arm's reach. Capture petrol in an appropriate container. Relieve pressure from the fuel system before removing the existing fuel pump. Pinching off the suction hose will minimize the amount of spilled gas. Special U-style clamps are made for this purpose, although DIY mechanics often improvise with small C-clamps or locking pliers using something to protect the fuel line from the pliers' jaws. The OEM sliding-style hose clamps are realistically one-use only. Spring-type clamps are DIY-friendly and are normally packaged with the new fuel pump. In a pinch, worm-gear clamps have decades of proven effectiveness, providing they aren't over or under tightened.

The fuel suction dampener is located under the car on the right side below the fuel filling inlet near the fuel tank. You'll need to jack up the rear of the vehicle and put the rear of the car on jack stands. Check out our article on safely jacking up your car to make sure you're doing this properly. Always wear safety glasses whenever you work under your vehicle.

Using a 13mm socket, loosen and remove the two bolts that hold the plastic protective shield.
Figure 1

Using a 13mm socket, loosen and remove the two bolts that hold the plastic protective shield.

Using an 8mm socket, loosen and remove the two nuts that secure the clamp for the fuel pump.
Figure 2

Using an 8mm socket, loosen and remove the two nuts that secure the clamp for the fuel pump.

Using a flat face screwdriver, loosen the clamp that holds the fuel line on the fuel pump.
Figure 3

Using a flat face screwdriver, loosen the clamp that holds the fuel line on the fuel pump. Even if the fuel line is clamped shut, place a proper receptacle to catch any fuel that is in the lines.

Using an 8mm open-end wrench, loosen and remove the two nuts that secure the electrical terminals on the fuel pump.
Figure 4

Using an 8mm open-end wrench, loosen and remove the two nuts that secure the electrical terminals on the fuel pump.

Using a 10mm socket, loosen and remove the nut towards the rear that secures the fuel delivery system.
Figure 5

Using a 10mm socket, loosen and remove the nut towards the rear that secures the fuel delivery system.

Using a 10mm socket, loosen and remove the nut towards the front that secures the fuel delivery system.
Figure 6

Using a 10mm socket, loosen and remove the nut towards the front that secures the fuel delivery system.

Using a 17mm open-end wrench, loosen and remove the fuel line from the rear of the fuel pump.
Figure 7

Using a 17mm open-end wrench, loosen and remove the fuel line from the rear of the fuel pump. Make sure that a proper fuel receptacle is in place to catch any fuel that may leak from the pump.

Using a flat face screwdriver loosen the hose clamp that secures the fuel line going to the fuel suction dampener.
Figure 8

Using a flat face screwdriver loosen the hose clamp that secures the fuel line going to the fuel suction dampener. Make sure that a proper fuel receptacle is in place to catch any fuel that may leak from the fuel suction dampener.

The fuel suction dampener is now free and ready to be replaced.
Figure 9

The fuel suction dampener is now free and ready to be replaced. Replacement is the reverse of removal.

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Comments and Suggestions:
brian Comments: hi I have a Mercedes 450sl convertible ser 10704412039821
1978 engine bay fire only damage was wiring and vacume hoses need a scimatic of were the new ones go don't wont to guess kind regards brian
July 29, 2015
  Followup from the Pelican Staff: I don't have that wiring to share.

I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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