The electrical system which is of 12 volt negative
circuit is open. When the switch is turned ON, the relay
ground polarity consists of the following circuits; starting,
becomes energized ungrounding the magneto and
magneto tachometer, hour meter, oil pressure and high
tachometer and closing the circuit to the engine hour
temperature safety. Power is furnished by the main
meter. The circuit to the oil pressure gage is completed
vehicle batteries through a connecting point at the diesel
directly through the ignition switch.
engine starter terminal.
The high temperature safety switch will short out the
The relay has two sets of contacts; one set completes
ignition by grounding the magneto when the engine
the magneto and tachometer circuit, and the other
temperature becomes excessive.
completes the engine hour meter circuit. When the
ignition switch is in the OFF position, the magneto and
FIGURE 7. WIRING DIAGRAM
In a new engine or one which has been out of operation
for some time, oil may have drained off the cylinders so
that compression will be weak, causing difficulty in
starting. To remedy this condition, remove the spark
plugs and pour about a fluid ounce of crankcase oil
through the spark plug hole into each cylinder. Turn
engine over several times with the hand crank to
distribute oil over the cylinder walls. Assemble spark
plugs and compression should be satisfactory.
SPARK PLUGS, Fig. 8
Incorrect gap, f6ulWd,4l , worn spark plug electrodes,
will have an adverse affect on engine operation.
Remove spark plugs periodically, clean, reg ap or
replace if necessary. Thread size is 18 mm.
HIGH TEMPERATURE SAFETY SWITCH
As a safety precaution against overheating, engines can
Spark plug gap 0.030 of an inch.
be equipped with a high temperature switch mounted to
the cylinder head at the No. 4 spark plug.
Replacement spark plugs must be special type YD311SI
for use in shielded ignition systems. Tighten spark
When cylinder head temperature becomes critically
plugs, 25 to 30 foot pounds torque.
high, the safety switch will automatically stop the
.engine by shorting out the ignition system. A waiting