TM 5-3810-300-24&P-3
15.2
TROUBLESHOOTING
Certain abnormal conditions which sometimes interfere
d. If the cylinder still misfires, remove the cam
with satisfactory engine operation, together with methods
follower (refer to Section 1.2.1) and check for a
of determining the cause of such conditions, are covered
scorn cam roller, camshaft lobe, bent push rod
on the following pages.
or worn rocker arm bushings.
Satisfactory engine operation depends primarily on:
7. If installation of a new injector does not eliminate
the misfiring, check the compression pressure of the
1. An adequate supply of air compressed to a
cylinder in question.
sufficiently high compression pressure.
Checking Compression Pressure
2. The injection of the proper amount of fuel at the
right time.
Compression pressure is affected by altitude as shown in
Table 1.
Lack of power, uneven running, excessive vibration,
stalling at idle speed and hard starting may be caused by
Check the compression pressure as follows
either low compression, faulty injection in one or more
cylinders, or lack of sufficient air.
Since proper compression, fuel injection and the proper
amount of air are important to good engine performance,
detailed procedures for their investigation are given as
follows: Locating a Misfiring Cylinder
1. Start the engine and run it at part load until it
reaches normal operating temperature.
2.
Stop the engine and remove the valve rocker cover.
3.
Check the valve clearance.
4. Start the engine. Then hold an injector follower
down with a screw driver (Fig I) to prevent operation of
the injector If the cylinder has been misfiring, there will
be no noticeable difference in the sound and operation of
the engine
If the cylinder has been firing properly,
there will be a noticeable difference in the sound and
operation when the injector follower is held down. This is
similar to short-circuiting a spark plug in a gasoline
engine.
Fig. 1 - Locating a Misfiring Cylinder
5. If the cylinder is firing properly, repeat the
procedure on the other cylinders until the faulty one has
been located.
6.
If the cylinder is misfiring. check the following:
a. Check the injector timing (refer to Section 14.
).
b. Check the compression pressure.
c. Install a new injector.
Table 1
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