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3. If
“
Continuity” is not measured in Step 5, repair
or replace Wire 0 between the Fuel Solenoid and
ground terminal.
4. If
“
Continuity” is not measured in Step 6, repair or
replace Carburetor ground wire.
5. If the Fuel Solenoid operates, proceed to Test 29.
TEST 29 – CHECK IGNITION SPARK
DISCUSSION:
A problem in the engine ignition system can cause
any of the following:
• Enginewillnotstart.
• Enginestartshard,runsrough.
A commercially available spark tester may be used to
test the engine ignition system. One can also be pur-
chased from Generac Power Systems (P/N 0C5969).
PROCEDURE:
1. Disconnect a high tension lead from a spark plug.
2. Attach the high tension lead to the spark tester
terminal.
3. Ground the spark tester clamp by attaching to the
cylinder head (see Figure 7-32).
SPARK TESTER CLAMP
GROUNDED TO
CYLINDER HEAD
SPARK TESTER
SPARK PLUG
BOOT
Figure 7-32. – Testing Ignition System
4. Crank the engine rapidly. Engine must be crank-
ing at 350 rpm or more. If spark jumps the tester
gap, you may assume the ignition system is work-
ing properly. Repeat on remaining cylinder spark
plug.
5. To determine if an engine miss is ignition related,
connect the spark tester in series with the high
tension lead and the spark plug. Then, start the
engine. If spark jumps the tester gap at regu-
lar Intervals, but the engine miss continues, the
problem may be in the spark plug or fuel system.
Repeat on remaining cylinder spark plug. Proceed
to Test 30.
6. If spark jumps the tester gap intermittently, the
problem may be in the Ignition Magneto. Proceed
to Test 31.
SPARK TESTER CLAMP
CONNECTED TO
SPARK PLUG
SPARK TESTER
SPARK PLUG
BOOT
Figure 7-33. – Checking Engine Miss
RESULTS:
1. If no spark or if engine miss is apparent, go to
Test 31.
2. If ignition spark is good, go to Test 30.
CYLINDER BALANCE TEST:
If the engine is hard starting, runs rough, misses or
lacks power, perform a cylinder balance test to deter-
mine whether both cylinders are operating to their full
potential.
Tools Required:Two Ignition Testers (Generac P/N
0C5969)
Attach an ignition tester between the spark plug lead
and each spark plug (Figure 7-33).
Start and run engine running at top no load speed
and note spark at ignition testers. If the spark is equal
at both ignition testers, the problem is not ignition
related. A spark miss will be readily apparent. Now
note RPM of engine. Ground out one cylinder by con-
tacting ignition tester and a good ground on engine as
shown in Figure 7-34. Note RPM loss. Reattach plug
wire then repeat procedure with the other cylinder.
Note the RPM loss. If the difference between the two
cylinders does not exceed 75 RPM, the amount of
work the two cylinders are doing should be consid-
ered equal.
If the RPM loss is greater than 75 RPM this indicates
that the grounded cylinder with the least RPM loss is
the weakest of the two cylinders. Look to that cylinder
for a problem.
Example:
Engine RPM - Both Cylinders = 2570 RPM
Engine RPM - No. 1 Cylinder Grounded = 2500 RPM
Engine RPM - No. 2 Cylinder Grounded = 2300 RPM
Conclusion: No. 1 cylinder is weakest of the two cylinders.
Page 54
Section 7
DIAGNOSTIC TESTS