DETROIT DIESEL
Engine Tune-Up
LIMITING SPEED MECHANICAL GOVERNOR AND INJECTOR RACK
CONTROL ADJUSTMENT
IN-LINE ENGINES
The double-weight limiting speed governor is mounted
3. Start the engine and adjust the idle speed screw
on the rear end plate of the engine and is driven by a
(Fig. 7) to obtain the desired engine idle speed. Hold
gear that extends through the end plate and meshes
the screw and tighten the lock nut to hold the
with either the camshaft gear or the balance shaft
adjustment.
gear, depending upon the engine model.
NOTE: The recommended idle speed for non-
After adjusting the exhaust valves and timing the fuel
EPA certified engines is 500-600 rpm, but may
injectors, adjust the governor and position the injector
vary with special engine applications.
rack control levers.
4. Stop the engine, clean and remove the governor
cover and the valve rocker cover. Discard the gaskets.
NOTE: Before proceeding with the governor and
injector rack adjustments, disconnect any
5. Start and run the engine, between 800 and 1000 rpm
supplementary governing device. After the
by manual operation of the injector control tube lever.
adjustments are completed, re-connect and
adjust the supplementary governing device.
CAUTION: Do not overspeed the engine.
6. Check the gap between the low-speed spring cap
and the high-speed spring plunger with a .0015" feeler
Adjust Governor Gap
gage. If the gap setting is incorrect, reset the gap
adjusting screw (Fig. 1). If the setting is correct, the
With the engine stopped and at operating tempera-
.0015" movement can be seen by placing a few drops
ture, adjust the governor gap as follows:
of oil into the governor gap and pressing a screw
driver against the gap adjusting screw. Movement of
1. Remove the high-speed spring retainer cover.
2. Back out the buffer screw (Fig. 8) until it extends
approximately 5/8" from the lock nut.
Fig. 2 - Positioning the Rear Injector Rack
Fig. 1 - Adjusting Governor Gap
Control Lever
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