Generac Power Systems GP Series Diagnostic Repair Manual page 47

and the crankcase breather. This will help
determine where the fault lies.
Repeat Steps 1–9 on remaining cylinder if
10.
applicable.
Results
• Air escapes at the air intake – check intake valve.
Air escapes through the exhaust – check exhaust
•
valve.
• Air escapes through the breather – check piston
rings.
• Air escapes between the cylinder head and block –
replace head gasket and check both gasket
surfaces.
When done with testing reassemble unit and return to
normal operation.
Test 18 – Check Ignition Coils
(IC1, IC2)
General Theory
Major components of the ignition system include
• Ignition coil assembly
• Spark plug
• ECM
The ECM adjusts ignition spark timing based on engine
and load and temperature conditions.
See Figure 5-76. The ignition coil assembly consists of
(a) ignition coil, (b) spark plug high tension lead, and (c)
spark plug boot.
C
B
Figure 5-76. Ignition Coil
Procedure A
Verify engine turns over correctly and no other
1.
faults are displayed.
Use a spark tester to verify spark output from the
2.
coil to ground.
If unit fails to produce spark, perform Procedure B.
3.
Procedure B
See Figure 5-77. Locate and disconnect CONN1P
1.
Connector B located behind the panel.
Diagnostic Repair Manual
Procedure C
A
014997
Procedure D
Section 5 Engine Diagnostic Tests
Figure 5-77. CONN1P Connector
See Figure 5-78. Disconnect and measure the
2.
resistance from IC1 and IC2 Connectors directly to
coils IC-1 and IC-2.
• The primary resistance for IC-1 and IC-2 is
approximately 1.2 ohms.
IC1
IC2
Figure 5-78. Ignition Coils IC1 and IC2
With CONN1P Connector still disconnected check
3.
all four (4) pins to frame ground.
• Continuity should NOT be measured.
• If continuity is measured, replace ignition coils and
engine harness.
Set DMM to measure resistance.
1.
Disconnect spark plug boot from spark plug.
2.
Connect one test lead to spark plug boot.
3.
Connect the other test lead to ground.
4.
• Continuity should NOT be measured.
•
Repeat for both cylinders
Keep one test lead in the spark plug boot. Use the
5.
other test lead (used to check ground in Step 4) to
check resistance to:
a. Pin 14C of the CONN1P Connector IC-1.
b. Pin 451 of the CONN1P Connector IC-1.
c. Pin 14C of the CONN1P Connector IC-2.
d. Pin 452 of the CONN1P Connector IC-2.
• Approximately 17.2 ohms should be measured.
Reconnect spark plug boot.
6.
If Procedures A, B and C are good keep CONN1P
1.
Connector disconnected.
Disconnect the ECM connector.
2.
Check Wires 14C, 451 and 452 from the CONN1P
3.
Connector to the ECM connector for:
a. continuity
b. shorts between wires
015013
A B C
451 ECM-4M
14C SPLICE 5
A B C
452 ECM-1M
14C SPLICE 5
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