11 37... Fault patterns, valve gear (N20/26/N55)

WARNING: The preloading on the throttle return springs increases as the rotation on the worm gear increases. Danger of injury!

The eccentric shaft may only be twisted on the mounting flats for protection.

Risk of damage to the eccentric shaft gearing and to the servomotor worm drive.

The eccentric shaft must not spring back to the minimum stroke stop. Risk of damage !

Necessary preliminary tasks:

WARNING: Heed stop installation instructions.

The eccentric shaft on the mounting flats (2) must only be turned with an open-end spanner (1) for support.

The eccentric shaft has mounting flats on both sides; if the engine is installed, the front mounting flat must be used.

Heed the following work instructions.

Fig 1: Turning Mounting Flats Eccentric Shaft Using Open-End Spanner

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After the engine stops, the eccentric shaft is in the maximum stroke position.

If the actuator drive is defective, the eccentric shaft is located in an undetermined position.

Check throttle return spring (2) for breakage and correct installation position on intermediate lever (1).

Check roller cam follower (3) for correct installation position.

Fig 2: Locating Valve Gear Throttle Return Spring

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Check that intermediate lever (1) is correctly seated.

NOTE: Illustration does not show sliding block.

Fig 3: Identifying Valve Gear Intermediate Lever

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Check wear at stop (1) - minimum lift and maximum lift.

Check that stops are securely seated.

Tightening torque: 11 37 5AZ .

Fig 4: Identifying Valve Gear Stop

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Stiff movement in eccentric shaft bearing is excluded.

Stiff movement can occur in worm gear.

Fig 5: Securing Eccentric Shaft Using Special Tool (11 7 170)

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Assemble engine.