TESTING AND ADJUSTING
AIR FUEL RATIO CONTROL ADJUSTMENTS (ON
3500 SERIES ENGINES)
ADJUSTMENT OF FUEL LIMIT LEVEL
There are three adjustments for the air fuel ratio
PNEUMATIC MID-SPEED CONTROL ADJUSTMENT
control. One is the fuel limit level adjustment screw, the
second is gain rate cam slide adjustment. The third is
The control cylinder mounts on the front of the
the cocking level setting. These last two are factory set
governor. An adjustable lever is fastened on the speed
and do not require adjustment. Any change to their
setting control shaft. The cylinder rod is spring-actuated
settings will require the governor to be put on a test
(extended) and air-retracted. With the cylinder retracted,
bench and correct settings made to test bench
and the speed setting shaft in the fuel shutoff position,
set the lever at 60 degrees below the horizontal
centerline. When the cylinder rod is extended the lever
To adjust the fuel limit level, remove the plug
will move the speed setting shaft in the "FUEI ON"
from the right front corner of the top cover. Put a 3/16
direction to 45 degrees below the horizontal centerline. If
inch hex wrench through the hole in the top cover until it
necessary, adjust the lever to achieve a 1400 rpm engine
engages the fuel limit level adjustment screw. Install and
zero the dial indicator on the side of the engine front
drive housing for checking fuel setting.
For an initial setting, turn the limit level screw in
until it stops, then back it out 10 turns (about mid-travel).
Start the engine and load it enough to generate boost of
10 inches of mercury to cock the control. Disconnect the
air pressure line from the control to the manifold.
Rapidly move the speed control shaft in the
speed increase direction. The dial indicator will go up to
the fuel limit position, pause momentarily, then drop
back. Do this several times and read the dial indicator
during each pause. Or, load the engine until the dial
indicator stops. Where the dial indicator pauses or
stops, is the limit travel setting of the control. Turn the
limit level screw until the dial indicator agrees with the
specifications given in the Fuel Setting and Related
When the adjustment is correct, connect the air
pressure line from the control to the manifold. Remove
the hex wrench and install the plug in the top cover.
Remove the dial indicator from the front drive housing.