12. VACUUM THROTTLE CONTROL OR VACUUM DASHPOT

The function of the vacuum throttle control or vacuum dashpot is:

1. To prevent stalling, when the throttle is suddenly closed. It insures a gradual or slow closing which permits the continuing air supply to lean out the rich mixture of fuel that occurs on sudden throttle closing.

2. It works with emission control. During coasting it holds the throttle plate open slightly.

3. It acts as an idle speed stabilizer when the engine is under load at idle. The plunger extends as the vacuum falls due to the load. This causes the throttles to be opened slightly.

Problems

If the dashpot or vacuum control is incorrectly adjusted the driver will experience:

1. Braking problems, if the throttle is held open too long.

2. Stalling.

Adjustment

VACUUM THROTTLE CONTROL

1. With engine idling, remove vacuum hose from throttle control. (See Fig. 1)

2. Set adjusting screw to provide an engine speed of 1100 to 1200 RPM. Caution: Late units have jam nut on screw which must be loosened first. (See Fig. 2)

3. Reconnect vacuum hose. (See Fig. 3)

4. Adjust compression spring with adjusting plate, so that play between actuating lever and adjustment screw is sufficient to slide a piece of paper through (0.1 mm). While adjusting nut do not allow screw to turn. (See Fig. 4)

VACUUM DASHPOT

(Early models only)

1. With engine off, hold actuating lever to the point where it just contacts the venting valve. (See Fig. 5)

2. Adjust dashpot plunger so that there is 2-3 mm. clearance between the carburetor lever and dashpot plunger. (See Fig. 6)