Table 4-1. Troubleshooting (Continued)
8 Engine speed cycles
a. Gas producer fuel
control bypass valve not
b. Check rigging
9 Engine unstable
above idle speed.
10 Idle speed too low.
a. Leak(s) in fuel system
b. Double check valve.
c. Contamination in the
pneumatic section of the
gas producer fuel control
and power turbine
d. Defective fuel control
f. Contaminated fuel
8. Incorrect gas producer
c. Excessive generator
d. Dirty compressor.
e. Gas producer fuel
control idle adjustment
f. Air sensing lines
g. Accumulator leaking.
a. Disconnect the fuel line at the
fuel nozzle; flush system with clean
fuel. Replace the fuel control fuel
filter. (Refer to para 5-12.) If the
same condition still exists, replace
control. (Refer to para 5-12.)
b. Refer to para 5-12.
a. Correct leak(s), then test in
accordance with para 5-8.
b. Replace double check valve.
c. Check Pg port in the governor
and the Pc port in both control and
governor. Replace control or
governor if contaminated. (Refer to
para 5-12 and 5-13.)
d. Isolate the governor from the
system by removing the tee fitting
from the governor Pc port and
capping the governor end of the tee.
Plug the open governor port to
prevent entry of dirt. Start the
engine and carefully accelerate to
100% N2 and check stability. If the
engine is unstable, replace the fuel
control; if stable, replace the
governor. (Refer to para 5-12 and
e. Replace accumulator(s).
f. Clean or replace the filter. (Refer
to para 5-12.)
a. Check lever position and rigging.
(Refer to para 5-12.)
b. Replace tachometer. (Refer to TM
c. Reduce electrical load
d. Clean compressor and bleed
valve. (Refer to para 7-3 and 7-7.)
e. Adjust idle setting, (Refer to para
f. Check for leaks. Tighten coupling
nuts as required.
g. Check for cracks in sheet metal
or braze. Replace accumulator if
leaks are found. (Refer to para 5-16.)
Change 23 4-5
If a crack in sheet metal or braze is
suspected, refer to TM 1-1520-254-23,
Technical Manual Aviation Unit Main-
tenance (AVUM) and Aviation Intermediate
Maintenance (AVIM) Manual Nondestructive
Inspection Procedure for OH-58 Helicopter Series