a. The troubleshooting procedures in this chapter
are presented as a guide for locating and correcting
malfunctions. Use of these procedures will reduce
delays and maintenance down time and will minimize
unnecessary replacement of engine components. Two
basic assumptions have been made in preparing these
procedures; (1) the correct operating procedures have
been followed and (2) the problem is caused by a single
failure or malfunction.
b. The troubleshooting procedures are organized
under three basic heading; (1) Trouble, (2) Probable
cause, and (3) Remedy.
c. The trouble as reported by the flight crew is the
main point of the problem. Obtain as much informa-
tion as possible from the flight crew and their report. In
many cases, this information will define the problem
completely, however, the malfunction should be con-
firmed by a ground run, providing there is no danger of
possible engine damage occurring.
d. The probable cause lists the components which
might cause the malfunction. The cockpit indications
can often give a clue as to which of these components is
causing the problem.
e. Caution must be exercised to avoid troubleshoot-
ing difficulties caused by false cockpit indications. In
most cases, a false indication can be detected by check-
ing it against other indications. For example, a TOT
indication system malfunction should be suspected if
TOT is high, low, or fluctuating with no change in fuel
flow or torque.
f. The remedy lists the action to be taken to correct
g. It is not possible to list troubleshooting pro-
cedures for every malfunction which can occur There
will be situations encountered for which there are no
applicable procedure but the methods and principles
used in the procedures are effective in all maintenance
Table 4-1. Troubleshooting
1 Engine fails to reach
light off cranking
2 Engine fails to light
off fuel vapor
coming out of exhaust
and no audible
a. Inadequate starter
torque caused by low
battery or defective
b. B and C leads on
terminal block reversed.
c. N1 binding.
a. Preservative oil
fouling spark igniter.
b. Faulty circuit to
a(1). Check battery.
a(2). Check for loose cables.
a(3). Check starter-generator and
replace if defective. (Refer to TM
b. Reverse B and C leads.
C(1). Check inlet for foreign object
damage. Rotate N1 by hand and
listen for abnormal noise.
c(2). Replace engine. (Refer to TM
a. Try a second start.
b. Check input power to exciter. If
no power, isolate defective
component and correct fault.
Change 14 4-1