Generac Power Systems GP Series Diagnostic Repair Manual page 45

Figure 5-70. Checking Engine Misfire
If spark jumps tester gap intermittently, the problem
5.
may be in the ignition coil or ignition control
system.
Results
Refer to flow chart.
Test 16 – Check Spark Plug(s)
Procedure
See Figure 5-71 and
plug(s). Clean with commercial solvent. Replace spark
plugs if badly fouled, if ceramic is cracked, or if badly
worn or damaged.
A B
D E
A. Normal
B. Mechanical Damage
C. Oil Fouled
Figure 5-71. Spark Plug Conditions
Figure 5-72. Setting Spark Plug Gap
Diagnostic Repair Manual
Figure 5-72. Remove spark
C
F
D. Overheated
E. Insulator Glazing
F. Pre-Ignition
Results
Clean and gap or replace spark plug(s) as neces-
1.
sary.
Refer to flow chart.
2.
Test 17 – Check Engine / Cylinder
Leak Down Test / Compression Test
Introduction
002075
Performing the following test procedures will accurately
diagnose some of the most common problems:
• Will not start
•
Lack of power
• Runs Rough
• Vibration
Check Compression
Lost or reduced engine compression can result in a failure
of the engine to start, or rough operation. One or more of
the following will usually cause loss of compression:
• Blown or leaking cylinder head gasket.
• Improperly seated or sticking-valves.
• Worn piston rings or cylinder (this will also result in
high oil consumption).
For air-cooled
compression pressure for a cold engine is typically 150
PSI. Compression values are based on accurate process
and proper procedure. However, testing has proven that
an accurate indication of compression in the cylinder can
be obtained by using the following procedure.
NOTE: Battery and starting system must be in good
condition to get accurate results.
IMPORTANT NOTE: Valve operation is critical to
proper compression testing. Verify valve operation is
correct before proceeding with test.
013032
Required Tools
•
Remote push button starter
Figure 1-73. Remote Push Button Starter
Procedure
Remove F1 and F2 fuses.
1.
000211
Set MLCB to OFF.
2.
Section 5 Engine Diagnostic Tests
• Overheating
•
High Oil Consumption
• Inability to carry full
load
engines, the minimum allowable
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