DETROIT DIESEL
Engine Tune-Up
SUPPLEMENTARY GOVERNING DEVICE ADJUSTMENT
ENGINE LOAD LIMIT DEVICE
Engines with mechanical governors may be equipped
Adjustment
with a load limit device (Fig. 1) to reduce the
After the engine tune-up is completed, make sure the
maximum horsepower.
load limit device is properly installed as shown in
Fig. 1. Make sure the counterbores in the adjusting
This device consists of a load limit screw threaded into
screw plate are up. The rocker arm shaft bracket bolts
which fasten the adjusting screw plate to the brackets
a plate mounted between two adjacent rocker arm
are tightened to 50-55 lb-ft (68-75 Nm) torque. Then
shaft brackets and a load limit lever clamped to the
adjust the load limit device, on each cylinder head, as
injector control tube.
follows:
1. Loosen the load limit screw lock nut and remove the
The load limit device is located between the No. 2 and
screw.
No. 3 cylinders of a three or four cylinder engine or
2. Loosen the load limit lever clamp bolts so the lever
between the No. 1 and No. 2 cylinders of each
is free to turn on the injector rack control tube.
cylinder head on a V-type engine. However, when
valve rocker covers with a breather are used, the load
3. With the screw out of the plate, adjust the load limit
screw lock nut so the bottom of the lock nut is
limit device is installed between the No. 1 and No. 2
7/8" from the bottom of the load limit screw (Fig. I)
cylinders on in-line engines and between the No. 2
for the initial setting.
and No. 3 cylinders on V-type engines to avoid
interference with the rocker cover baffles.
4. Loosen the load limit lever clamp bolts so the lever
is free to turn on the injector rack control tube.
When properly adjusted for the maximum horsepower
4. Thread the load limit screw into the adjusting screw
desired, this device limits the travel of the injector
plate until the lock nut bottoms against the top of the
plate.
control racks and thereby the fuel output of the
injectors.
5. Hold the injector rack control tube in the full-fuel
position and place the load limit lever against the
bottom of the load limit screw. Then tighten the load
limit lever clamp bolts.
6. Check to ensure that the injector racks will just go
into the full-fuel position -- readjust the load limit
lever if necessary.
7. Hold the load limit screw to keep it from turning,
then set the lock nut until the distance between the
bottom of the lock nut and the top of the adjusting
screw plate corresponds to the dimension (or number
of turns) stamped on the plate. Each full turn of the
screw equals .042", or .007" for each flat on the
hexagon head.
NOTE: If the plate is not stamped, adjust the
load limit screw while operating the engine on a
dynamometer test stand and note the number
o f turns required to obtain the desired
horsepower. Then stamp the plate accordingly.
8. Thread the load limit screw into the plate until the
lock nut bottoms against the top of the plate. Be sure
the nut turns with the screw.
9. Hold the load limit screw to keep it from turning,
Fig. 1 - Engine Load Limit Device
then tighten the lock nut to secure the setting.
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