TM 5-2420-230-24-2
roubleshooting Symptoms Charts
B3.9 and B5.9 Series Engines
Page TS-50
Section TS - Troubleshooting Symptoms
Engine Speed Surges at Low or High Idle
This is symptom tree T066.
Cause
Correction
Fill the supply tank. Refer to the OEM service
Fuel level is low in the tank
.......
manual.
OK
E
Check for added loading from malfunctioning
accessories or other engine-driven units,
ngine under excessive load
.......
brakes dragging, or other changes in vehicle
loading. Disengage engine-driven units.
OK
I
Check and adjust the low idle screw. Refer to
dle speed is set too low for accessories
.......
Procedure 005-029.
OK
T
Adjust or repair the linkage. Refer to Procedure
hrottle linkage misadjusted or damaged
.......
005-036.
OK
I
Check or adjust the bumper spring adjustment.
dle adjustment not correct
.......
Refer to Procedure 005-018.
OK
F
Check the fuel lines, fuel connections, and fuel
uel leak
.......
filters for leaks. Refer to Procedure 006-024.
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
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
I
Check the injectors and replace any malfunc-
njectors worn or malfunctioning
.......
tioning injectors. Refer to Procedure 006-026.
OK
T
(Continued)
L-634
