15.2
DETROIT DIESEL 53
TROUBLE S H O O T I N G
injector. If the cylinder has been misfiring, there will
Certain abnormal conditions which sometimes inter-
be no noticeable difference in the sound and operation
fere with satisfactory engine operation, together with
of the engine. If the cylinder has been firing properly,
methods of determining the cause of such conditions,
there will be a noticeable difference in the sound and
are covered on the following pages.
operation when the injector follower is held down.
Satisfactory engine operation depends primarily on.
This is similar to short-circuiting a spark plug in a
gasoline engine.
1. An adequate supply of air compressed to a
sufficiently high compression pressure.
5. If the cylinder is firing properly, repeat the
procedure on the other cylinders until the faulty one
2. The injection of the proper amount of fuel at the
has been located.
right time.
6. Provided the injector operating mechanism of the
Lack of power, uneven running, excessive vibration,
faulty cylinder is functioning satisfactorily, remove the
stalling at idle speed and hard starting may be caused
fuel injector and install a new one.
by either low compression, faulty injection in one or
more cylinders, or lack of sufficient air.
7. If installation of a new injector does not eliminate
the misfiring, check the compression pressure of the
Since proper compression, fuel injection and the
cylinder in question.
proper amount of air are important to good engine
performance, detailed procedures for their investiga-
tion are given as follows:
Checking Compression Pressure
Compression pressure is affected by altitude as shown
Locating a Misfiring Cylinder
in Table 1.
1. Start the engine and run it at part load until it
Check the compression pressure as follows:
reaches normal operating temperature.
1. Start the engine and run it at approximately one-
2. Stop the engine and remove the valve rocker
half rated load until normal operating temperature is
cover(s).
reached.
3. Check the valve clearance.
Altitude, Feet
Minimum Compression
Above Sea level
Pressure (psi) at 600 rpm
4. Start the engine. Then hold an injector follower
Std. Engine
down with a screw driver to prevent operation of the
0
430
2,500
400
5,000
370
7,500
340
10,000
315
TABLE 1
2. Stop the engine and remove the fuel pipes from the
injector and fuel connectors of the No. 1 cylinder.
3. Remove the injector and install adaptor J 7915-02
and pressure gage and hose assembly J 6992 (Fig. 1).
4. Use a spare fuel pipe to fabricate a jumper
connection between the fuel inlet and return manifold
connectors. This will permit fuel from the inlet
manifold to flow directly to the return manifold.
5. Start the engine and run it at a 600 rpm. Observe
Fig. 1 - Checking Compression Pressure
SEC. 15.2 Page 1
November, 1973
