Thermo King MD-MT, Operator'S Manual

Page: 92 / 192

Engine Maintenance
92
Troubleshooting the Integral Fuel
Solenoid System
NOTE: The fuel solenoid pull-in coil will
require 30 to 40 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. Disconnect the 20 wire from the reset switch
so the reset switch will not trip.
2. Disconnect the 8S wire from the starter
solenoid.
3. Disconnect the fuel solenoid wire connector
from the fuel solenoid.
4. Turn the unit ON and check the voltage on the
8D pin in the fuel solenoid wire connector
from the main wire harness. Refer to the
following illustration to identify the pins in
the wire connector and in the fuel solenoid.
a. If battery voltage is not present on the 8D
circuit, check the 8D circuit for an open or
a short.
b. If battery voltage is present on the 8D
circuit, go to step 5.
5. Check the CH pin in the fuel solenoid wire
connector for continuity to a good chassis
ground.
a. If there is no continuity between the CH
pin in the fuel solenoid wire connector and
a good chassis ground, check the black
(CH) wire that goes from the fuel solenoid
connector to the CH terminal on the
throttle solenoid for an open circuit.
b. If this black (CH) wire is not open, check
the other CH wire connected to the CH
terminal on the throttle solenoid for an
open circuit.
c. If there is continuity between the CH pin
in the fuel solenoid connector and a good
chassis ground, go to step 6.
6. Place a jumper wire between the CH pin in the
fuel solenoid and a good chassis ground.
7. Test the pull-in coil by momentarily placing a
jumper between the 8DP pin in the fuel
solenoid and the 2 terminal at the control
circuit. The fuel solenoid should make a
definite click when the pull-in coil is
energized and should click again when the
pull-in coil is de-energized.
NOTE: The pull-in coil will draw 18 to 25
amps so do not leave the jumper connected to
the 8DP pin for more than a few seconds.
a. If the pull-in coil does not energize, check
the resistance of the pull-in coil by placing
an ohmmeter between the 8DP pin and the
CH pin in the fuel solenoid. The resistance
of the pull-in coil should be -3 to -4 ohms.
If the resistance of the pull-in coil is not in
this range, replace the fuel solenoid.
NOTE: If the pull-in coil fails, make sure to
replace the fuel solenoid relay with a
Potter-Brumfield relay P/N 44-9111.
b. If the pull-in coil does energize, go to step
8.
8. Test the hold-in coil.
a. Energize the hold-in coil by placing a
jumper between the 8D pin in the fuel
solenoid and the 2 terminal at the control
circuit.
1. Pull Coil 8DP Color: White
2. 8D Hold Coil Color: Red
3. Common—Ground Color: Black CH
Figure 46: Fuel Solenoid Pin Identification