DETROIT DIESEL
SECTION 7
E N G I N E TUNE-UP PROCEDURES
There is no scheduled interval for performing an
Tune-Up Sequence for Mechanical Governor
engine tune-up. As long as the engine performance is
satisfactory, no tune-up should be needed. Minor
CAUTION: Before starting an engine after an
adjustments in the valve and injector operating
engine speed control adjustment or after
mechanisms, governor, etc. should only be required
removal of the engine governor cover, the
periodically to compensate for normal wear on parts.
serviceman must determine that the injector
racks move to the no-fuel position when the
Three types of governors are used. Since each
governor stop lever is placed in the stop
governor has different characteristics, the tune-up
position. Engine overspeed will result if the
procedure varies accordingly. The three types are:
injector racks cannot be positioned at no fuel
with the governor stop lever.
1. Limiting speed mechanical.
1. Adjust the exhaust valve clearance.
2. Time the fuel injectors.
2. Variable speed mechanical.
3. Adjust the governor gap.
3. Hydraulic.
4. Position the injector rack control levers.
5. Adjust the maximum no-load speed.
The mechanical engine governors are identified by a
name plate attached to the governor housing. The
6. Adjust the idle speed.
letters D.W.-L.S. stamped on the name plate denote a
double-weight limiting speed governor. A single-
7. Adjust the buffer screw.
weight variable speed governor name plate is stamped
S.W.-V.S.
8. Adjust the throttle booster spring (variable speed
governor only).
Normally, when performing a tune-up on an engine in
service, it is only necessary to check the various
9. Adjust the supplementary governing device (if
adjustments for a possible change in the settings.
used).
However, if the cylinder head, governor or injectors
have been replaced or overhauled, then certain
Tune-Up Sequence for Hydraulic Governor
preliminary adjustments are required before the
engine is started.
1. Adjust the exhaust valve clearance.
The preliminary adjustments consist of the first four
2. Time the fuel injectors.
items in the tune-up sequence. The procedures are the
same except that the valve clearance is greater for a
3. Adjust the fuel rod.
cold engine.
4. Position the injector rack control levers.
T o tune-up an engine completely, all of the
5. Adjust the load limit screw.
adjustments are made by following the applicable
tune-up sequence given below after the engine has
6. Adjust the speed droop.
reached the normal operating temperature. Since the
adjustments are normally made while the engine is
7. Adjust the maximum no-load speed.
stopped, it may be necessary to run the engine
NOTE: Use new valve rocker cover gasket(s)
between adjustments to maintain normal operating
after each tune-up.
temperature.
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