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