inches of water gauge air pressure). The switch contacts
All support equipment with automatic trans-
open, interrupting the circuit between the winding of
missions have some form of a neutral safety switch to
the starter relay or solenoid and ground.
eliminate the possibility of the engine starting with the
transmission selector lever in a position to drive the
When you shut the engine down, the contacts of the
lockout switch return to the closed position as oil or air
pressure decreases to a value below that required to
The switch is mounted on the transmission shift
actuate the lockout switch.
linkage or on the transmission case. When it is mounted
on the transmission shift linkage, it is connected in
MAINTENANCE AND REPAIR
series with the starter switch and the starter relay or
solenoid windings. When it is mounted in the
The starting system requires little maintenance if
transmission case, it is connected in series with the
used properly. If a malfunction does occur, you must
starter relay or solenoid winding and ground.
know how to troubleshoot the system and correct the
The shift lever actuates the switch. The switch is
open in all lever positions except neutral and park.
When the starter cranks the engine slowly (or not at
all), tests must be made to determine whether the
Starter Lockout Relay
malfunction is in the battery, starting motor, circuit
wiring, or some other component of the system. Many
This system is used to prevent the starter from
conditions besides defects in the starting motor can
being energized when the engine is running.
result in poor starter performance.
The normally closed contacts of the lockout relay
Prior to making any test, visually inspect the
connect in series with the starter switch and the starter
complete system. Ensure that all connections are clean
relay or solenoid winding. One end of the lockout relay
and tight, that the wiring is not frayed or otherwise
winding connects to the output of the generator; the
damaged, and check to determine that the starter
other end is to ground. When the generator output
mounting bolts are tight.
voltage reaches a value great enough to energize the
lockout relay, the lockout relay contacts open. This
There are many methods that can be used to test
opens the control circuit to the starter relay or solenoid
starting systems to determine their condition. Some of
winding. The contacts of the lockout relay remain open
these methods require the use of test equipment that
as long as generator output voltage is equal to or above
may not be available to you in fleet units. With this in
that required to energize the lockout relay. Connection
mind, the tests presented here are such that they may be
to generator output voltage is made at the generator so
performed using a minimum of test equipment.
that operation of the lockout relay is not dependent
upon operation of the generator regulator.
Battery Capacity Test
When the engine is shut down, the contacts of the
Remember that the starting system is completely
lockout relay return to the closed position as generator
dependent upon the battery for operation. Troubleshoot-
output voltage drops to a value below that required to
ing the starting system must begin with the battery.
energize the relay.
Specific gravity and open circuit voltage readings pro-
vide a general indication of battery condition. A more
Starter Lockout Switch
accurate indication can be obtained by making a capac-
ity test. Use a battery-starter tester for this purpose.
This device is used for the same purpose as the
starter lockout relay--to prevent the starter from being
NOTE: If the specific gravity of the battery is
energized when the engine is running. The switch is
1.220 or less, do not attempt to make a capacity test.
actuated by engine oil pressure, except when used with
The battery must be removed and slow-charged until
a two-stroke cycle diesel engine, when it is actuated by
fully charged before testing.
air pressure from the collector box of the engine blower.
To make a capacity test, the ampere-hour rating of
The diaphragm-operated lockout switch contacts
the battery must be known. This is generally stamped
are connected in series with the starter relay or solenoid
on the battery case. If it is not, refer to the man-
winding and ground. After you start the engine, oil or
ufacturer's instruction manual for the particular
air pressure builds up sufficiently to move the
diaphragm (usually 10 to 15 psi of oil pressure or 2 to 3