DETROIT DIESEL
Engine Tune-Up
Fig. 7 - Adjusting Idle Speed
Full-Load Speed
Stops
Shims
Solid
Split
1200-2100
1
1
As Required
2100-2500
1
0
As Required
2500-2800
0
0
As Required
*Maximum amount of shims .325"
TABLE 1
5. Connect the booster spring and the stop lever spring. Start the engine and recheck the maximum no- load speed.
6. If required, add shims to obtain the necessary operating speed. For each .001"in shims added, the operating speed
will increase approximately 2 rpm.
IMPORTANT: If the maximum no-load speed is raised or lowered more than 50 rpm by the installation or removal
of shims, recheck the governor gap. If readjustment of the governor gap is required, the position of the injector
racks must be rechecked.
NOTE: Governor stops are used to limit the compression of the governor spring, which determines the maximum
speed of the engine.
Adjust Idle Speed
With the maximum no-load speed properly adjusted, adjust the idle speed as, follows:
1. Place the stop lever in the run position and the speed control lever in the idle position.
Fig. 8 - Adjusting Buffer Screw
2. With the engine running at normal operating temperature, back out the buffer screw to avoid contact with the
differential lever.
3. Loosen the lock nut and turn the idle speed adjusting screw (Fig. 7) until the engine is operating at approximately 15
rpm below the recommended idle speed. The recommended idle speed is 550 rpm, but may vary with special engine
applications.
4. Hold the idle speed adjusting screw and tighten the lock nut.
Adjust Buffer Screw
1. With the engine running at normal operating temperature, turn the buffer screw in (Fig. 8) so that it contacts the
differential lever as lightly as possible and still eliminates engine roll.
NOTE: Do not raise the engine idle speed more than 15 rpm with the buffer screw.
2. Hold the buffer screw and tighten the lock nut.
Adjust Booster Spring
With the idle speed adjusted, adjust the booster spring as follows:
1. Move the speed control lever to the idle speed position.
2. Refer to Fig. 9 and loosen the booster spring
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