TM-9-2320-272-23-1
TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)
TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5
SEPTEMBER 2012
TM-9-2320-272-23-1 - Page 219 of 1313
FUEL SYSTEM (DUAL TANK) OPERATION
1.
The fuel system stores, cleans, and supplies fuel to the fuel injectors, where it is mixed with air to initiate
engine combustion.
2.
The fuel system is not identical for all models. Vehicles covered in this manual have either one or two tanks.
These tanks can also differ in capacity. See Table 4, Vehicle Performance Data, (WP
0002) for
these
differences.
3.
A typical dual tank fuel system is described below. A single tank fuel system is described later. Both systems
include fuel supply, return, and vent lines to provide fuel flow and release the fumes throughout the system.
Major components of the dual tank fuel system are:
A. RIGHT TANK (REAR) VENT LINE
- Vents vapors from fuel tank to vent hole in air intake stack.
B. RIGHT TANK FUEL SUPPLY LINE
- Directs fuel from tank to fuel filter.
C. RIGHT TANK FUEL LEVEL SENDING UNIT
- Electrical signal registers fuel level in right tank at gauge
on instrument panel.
D. LEFT TANK FUEL LEVEL SENDING UNIT
- Electrical signal registers fuel level in left tank at gauge on
instrument panel.
E. LEFT TANK FUEL SUPPLY LINE
- Directs fuel from tank to fuel filter.
F. LEFT FUEL TANK
- Stores fuel for vehicle use.
G. LEFT TANK (REAR) VENT LINE
- Vents vapors from fuel tank to vent hole in air intake stack.
H. LEFT TANK FILLER CAP
- Covers fuel filler opening on left fuel tank.
I. LEFT TANK FUEL RETURN LINE
- Returns unused fuel back to fuel tank.
J. LEFT TANK (FRONT) VENT LINE
- Vents vapors from fuel tank to vent hole in air intake stack.
K. FUEL SELECTOR VALVE
- Manual control valve that opens fuel flow to engine from left or right
fuel
tank.
L. FUEL FILTER/WATER SEPARATOR
- Filters water and dirt from fuel.
M. FUEL FILTER-TO-PUMP SUPPLY LINE
- Directs fuel from fuel filter to fuel pump.
N. FUEL RETURN LINE
- Returns unused fuel back to fuel tanks.
O. FUEL PRIMER PUMP
- Purges air from fuel system.
P. FUEL PUMP
- Draws fuel from tank(s) and pumps it through supply line to fuel injectors.
Q. FUEL SUPPLY LINE
- Directs fuel from fuel pump to fuel injectors.
R. RIGHT TANK (FRONT) VENT LINE
- Vents vapors from fuel tank to vent hole in air intake stack.
S. RIGHT TANK FILLER CAP
- Covers fuel filler opening on right fuel tank.
T. RIGHT FUEL TANK
- Stores fuel for vehicle use.
U. RIGHT TANK FUEL RETURN LINE
- Returns unused fuel back to fuel tank.
TM 9-2320-272-23-1
0003
0003-14
Back to Top
