Engine Tune-Up
DETROIT DIESEL
J 5895 and withdraw the high-speed spring and plunger
speed adjusting screw (Fig. 8) until the engine is
assembly.
operating at approximately 15 rpm below the
recommended idle speed.
CAUTION: To prevent the low-speed spring and
NOTE: The recommended idle speed for non-
cap from dropping into the governor, be careful
EPA certified engines is 500-600 rpm, but may
not to jar the assembly while it is being
vary with special engine applications.
removed.
If the engine has a tendency to
stall during
b. Remove the high-speed spring from the high-
deceleration, install a new buffer screw.
The current
speed spring plunger and add or remove shims
buffer screw uses a heavier spring and
restricts the
as required to establish the desired engine no-
travel of the differential lever to the
off (no-fuel)
load speed.
position.
NOTE: For each .010"in shims added, the engine
2.
Hold the idle screw and tighten the lock nut.
speed will be increased approximately 10 rpm.
3.
Install the high-speed spring retainer cover and
c. Install the high-speed spring on the plunger and
tighten the two bolts.
install the spring assembly in the governor
housing.
Install the spring retainer in the
Adjust Buffer Screw
governor housing and tighten it securely. The
maximum no-load speed varies with the full-
With the idle speed properly set, adjust the buffer screw
load operating speed desired.
as follows:
d. Start the engine and recheck the no-load speed.
1.
With the engine running at normal operating
Repeat the procedure as necessary to establish
temperature, turn the buffer screw in (Fig. 9) so it
the no-load speed required.
contacts the differential lever as lightly as possible and
still eliminates engine roll.
Adjust Idle Speed
NOTE: Do not increase the engine idle speed
With the maximum no-load speed properly adjusted,
more than 15 rpm with the buffer screw.
adjust the idle speed as follows:
2.
Recheck the maximum no-load speed. If it has
1.
With the engine running at normal operating
increased more than 25 rpm, back off the buffer screw
temperature and with the buffer screw backed out to
until the increase is less than 25 rpm.
avoid contact with the differential lever, turn the idle
3.
Hold the buffer screw and tighten the lock nut.
Fig. 9 - Adjusting Buffer Screw
Fig. 8 - Adjusting Engine Idle Speed
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