TM 5-4520-240-14
d. Installation. Installation of the fuel pump is the
WARNING
reverse of removal; refer to figure 4-10. Make the fuel
Clean parts in a well-ventilated area.
line and electrical connections. Install the top and side
Avoid inhalation of solvent fumes and
cover panels, and check for proper operation.
prolonged exposure of skin to cleaning
solvent, Wash exposed skin
4-23. Carburetor and Solenoid Valve.
thoroughly. Dry cleaning solvent (fed.
a. Fuel Adjustment. When the type of fuel being
spec. P-D-680) used to clean parts is
burned in the heater is changed, or when the heater is
potentially dangerous to personnel
subjected to extremely low ambient temperatures, it
and property. Do not use near open
will normally be necessary to readjust the fuel adjust-
flame or excessive heat. Flash point of
ment needle (8, fig. 4-7) on the carburetor for proper
solvent is 100F (38C).
(3) Clean the parts with dry cleaning solvent (fed.
NOTE
spec. P-D-680) and allow all parts to dry thoroughly
You can adjust the fuel adjustment needle without
removing the side cover panel. Depending on which
before reassembly. Replace the fuel pump filter ele-
cover is installed on the side of the heater, you can
ment if it cannot be cleaned with cleaning solvent, or if
make the adjustment through the ventilation air inlet
it is cracked or damaged. Check the magnet in the
screen or through the access hole after removing the
cover to make sure all metal chips are removed.
plug (2, fig. 4-4).
(4) Install the filter element (4, fig. 4-11) in the fuel
(1) If heater smokes, turn the fuel adjustment
pump (5). Make sure the filter element is fully seated
needle 1/8 turn clockwise to reduce the fuel flow. Ob-
and install the cover (2) using a new gasket (3). Secure
serve heater operation for 1 minute. If smoking per-
with the three screws (1).
sists, turn the needle an additional 1/8 turn and observe
(5) Open the fuel supply valve and connect the
operation. Continue until operation is satisfactory.
power plug. With the cover panels still removed, start
(2) If heater operation is erratic, or if heater fails
the heater and check for leaks around the fuel pump
to operate properly in extremely low ambient tem-
filter cover. If any leakage is detected, shut off the
peratures, turn the fuel adjustment needle 1/8 turn
heater, disconnect the power plug, and correct the leak.
counterclockwise to increase fuel flow. Observe opera-
Retest heater operation and, when it is satisfactory,
tion for 1 minute. Continue to turn the needle coun-
reinstall the cover panels.
terclockwise 1/8 turn at a time until heater operation is
b. Removal.
satisfactory. When heater is burning smoothly, there
(1) Disconnect the power plug and shut off the fuel
should be little or no smoke from the exhaust outlet.
supply.
b. Removal and Disassembly.
(2) Remove the top and side cover panels for access
WARNING
to the fuel pump.
The ignition system of this space
(3) Disconnect the fuel tubes (3 and 14, fig. 4-10)
heater contains dangerous voltages
from the fuel pump (19). Disconnect the fuel pump
which can cause severe electrical
electrical lead at the connector.
shock. Be sure to disconnect the power
(4) Remove the two nuts (17) and lock washers (18)
plug before repairing the heater.
that secure the fuel pump (19) to the bottom of the
(1) Disconnect the power plug and shut off the fuel
heater case; remove the fuel pump and pad (20).
supply. Remove the top and side cover panels for access
c. Cleaning and Inspection.
to the carburetor.
WARNING
(2) Tag and disconnect the fuel preheat thermostat
Clean parts in a well-ventilated area.
leads and the leads from the fuel solenoid valve (7, fig.
Avoid inhalation of solvent fumes and
4-7).
prolonged exposure of skin to cleaning
(3) Disconnect the compression nut (12, fig. 4-10) of
solvent. Wash exposed skin
the fuel tube (14) at the elbow (15) in the carburetor fuel
thoroughly. Dry cleaning solvent (fed.
inlet, and remove the elbow. Disconnect the overflow
spec. P-D-680) used to clean parts is
tube (21) from the elbow (23) on the top of the carbure-
potentially dangerous to personnel
tor (26). Remove the overflow tube and the tube (22).
and property. Do not use near open
(4) Remove the four screws (24) and lock washers
flame or excessive heat. Flash point of
(25) securing the carburetor to the burner head, and
solvent is 100F (38C).
remove the carburetor.
(1) Clean the exterior of the fuel pump with a cloth
(5) Unscrew the fuel adjustment needle (1, fig.
dampened with dry cleaning solvent (fed. spec. P-
4-12) and remove the preformed packing (2) from the
D-680). Dry thoroughly.
groove in the needle. Remove the two screws (3) and
(2) Inspect the fuel pump for cracks, damaged
lock washers (4) securing the preheat thermostat (5) to
threads, damaged electrical lead or connector, and
the carburetor (15), and remove the thermostat.
other visible damage; replace a defective fuel pump.
4-17
