TM 5-2420-230-24-2
roubleshooting Symptoms Charts
B3.9 and B5.9 Series Engines
Page TS-46
Section TS - Troubleshooting Symptoms
Engine Runs Rough at Idle
This is symptom tree T061.
Cause
Correction
Allow the engine to warm to operating tem-
perature. If the engine will not reach operating
Engine is cold
.......
temperature, refer to the Coolant Temperature
Below Normal symptom tree.
OK
I
Check and adjust the low idle screw. Refer to
dle speed is set too low for accessories
.......
Procedure 005-029.
OK
E
Verify the condition of the mounts. Refer to
ngine mounts are worn, damaged, loose, or
.......
Procedure 016-010. Refer to OEM service
not correct
manual.
OK
F
Check the fuel lines, fuel connections, fuel
delivery valve seals, and fuel filters for leaks.
uel leak
.......
Check the fuel lines from the supply tank(s).
Refer to the OEM's service manual.
OK
A
Check for air in the fuel system. Repair source
ir in the fuel system
.......
of leak and bleed air from the system. Refer to
Procedure 006-003.
OK
F
Check the flow through the fuel filter. Replace
the fuel filter if necessary. Refer to Procedure
uel filter or fuel inlet restriction
.......
006-015. Clean all prefilters and screens.
Check the fuel suction line for restriction.
OK
F
Inspect the fuel transfer pump. Replace if
uel transfer pump malfunctioning
.......
necessary. Refer to Procedure 005-045.
OK
F
uel pump return overflow valve is malfunction-
Inspect the return overflow valve. Replace if
.......
ing
necessary. Refer to Procedure 006-044.
OK
T
(Continued)
L-630
