Certain abnormal conditions which sometimes interfere
d. If the cylinder still misfires, remove the cam
with satisfactory engine operation, together with
methods of determining the cause of such conditions
worn cam roller. camshaft lobe, bent push rod
are covered on the following pages.
or worn rocker arm bushings.
Satisfactory engine operation depends primarily on:
Checking Compression Pressure
An adequate supply of air compressed to a
Compression pressure is affected by altitude as shown
sufficiently high compression pressure.
The injection of the proper amount of fuel at the
Check the compression pressure as follows:
Start the engine and run it at approximately one-
Lack of power, uneven running, excessive vibration,
half rated load until normal operating temperature is
stalling at idle speed and hard starting may be caused
by either low compression, faulty injection in one or
more cylinders, or lack of sufficient air.
Stop the engine and remove the fuel pipes from
the injector and fuel connectors of the No. 1 cylinder.
Since proper compression, fuel injection and the proper
amount of air are important to good engine
Remove the injector and install an adaptor and
performance, detailed procedures for their investigation
pressure gage from Diagnosis Kit J 9531-01 (Fig. 2).
are given as follows:
Use one of the fuel pipes as a jumper connection
Start the engine and run it at part load until it
reaches normal operating temperature.
Stop the engine and remove the valve rocker
Start the engine. Then hold an injector follower
down with a screwdriver to prevent operation of the
injector (Fig. 1). 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
If the cylinder is firing properly. repeat the
procedure on the other cylinders until the faulty one has
If the cylinder is misfiring, check the following:
a. Check the injector timing (refer to Page 10-10-
b. Check the compression pressure.
c. Install a new injector.