Thermo King UT-1200, Manual

Page: 105 / 169

Engine Maintenance
105
Fuel Limit Screw
The fuel limit screw is not adjustable. It is
equipped with an anti-tamper cap to fulfill
requirements for CARB (California Air Resources
Board) emission regulations. Service technicians
must be CARB certified to perform service on the
fuel limit screw for equipment operating in
California.
Figure 176: Emission Control Label
Fuel Solenoid
The fuel solenoid is located on the end of the
injection pump. It contains two coils: the pull-in
coil, and the hold-in coil. The pull-in coil draws
approximately 35 to 45 amps at 12 volts. The
hold-in coil draws approximately 0.5 amps at
12 volts.
The pull-in coil must be momentarily energized to
move the fuel rack to the on position. Once the
fuel rack has been moved to the on position, the
hold-in coil will then hold the fuel rack in the on
position until the 8D circuit is de-energized. The
pull-in coil must be de-energized after a few
seconds to keep it from being damaged. The
pull-in coil is controlled by the microprocessor
through the fuel solenoid pull in relay (K6).
Testing the Fuel Solenoid
NOTE: The fuel solenoid pull-in coil will
require 35 to 45 amps to turn on the fuel. The
unit’s battery must be in good condition. If the
battery has enough power to crank the engine
over, it has enough power to energize the fuel
solenoid pull-in coil.
If you suspect that the engine does not run
because the fuel solenoid is not operating
correctly, use the following procedure:
1. Use the Mechanics/Premium HMI Control
Panel to enter the Interface Board Test Mode.
Refer to the appropriate Microprocessor
Diagnostic Manual for specific information
about the Interface Board Test Mode.
2. Energize the run relay with the Interface
Board Test Mode. The fuel solenoid relay is
momentarily energized when the run relay is
energized with the Interface Board Test Mode.
This energizes the fuel solenoid, which makes
a definite click when energized.
3. De-energize the run relay with the Interface
Board Test Mode. This de-energizes the fuel
solenoid, which makes a definite click when
de-energized.
4. Repeat steps 2 and 3 a few times to check the
operation of the fuel solenoid.
NOTE: The fuel solenoid may be removed
from the injection pump to visually check its
operation. The fuel solenoid must be
energized when it is re-installed in the injection pump. If it is not, the plunger and
the linkage may not line up correctly and the
fuel solenoid will not function properly.
1. Fuel Solenoid
Figure 177: Fuel Solenoid Location
1