Kohler COMMAND CV17-745 Service Manual page 111

Kohler Engine Parts Call K&T 606-678-9623 or 606-561-4983
Operation: The ignition module for this system
operates in the same fashion as the fixed timing
module, except the trigger circuit for the
semiconductor (L2, Figure 8-5) is replaced by the
spark advance module (Figure 8-7).
The pulse generated by the input coil of the ignition
module (L1, Figure 8-5) is fed to the input of the
conditioning circuit. The conditioning circuit shapes this
pulse, putting it in a useable form for the additional
circuits. This pulse starts the charge pump, which
charges a capacitor in a linear fashion that can be
directly related to the engine speed. At the same time
the pulse resets the delay circuit for length of the pulse
width. The comparator is off during this period and no
output is generated. As soon as the original pulse
drops back to zero, the capacitor in the delay circuit
begins to charge.
When the charge on the delay capacitor exceeds the
charge on the charge pump capacitor the comparator
changes state, activating the pulse generator. This
pulse turns "ON" the CD ignition module
semiconductor. Energy is then transferred to the
secondary of the output transformer (T1, Figure 8-5).
The high voltage pulse generated here is delivered to
the spark plug, causing arcing of the spark gap and
igniting the fuel-air mixture in the combustion chamber.
As the trigger pulse is generated, all associated
circuits are reset, their capacitors discharged. The
longer it takes the delay circuit to surpass the charge
pump capacitor voltage, the later the trigger pulse will
occur, retarding the timing accordingly.
Troubleshooting CD Ignition Systems
The CD ignition systems are designed to be trouble
free for the life of the engine. Other than periodically
checking/replacing the spark plugs, no maintenance or
timing adjustments are necessary or possible.
Mechanical systems do occasionally fail or break
down, however, so the following troubleshooting
information is provided to help you get to the root of a
reported problem.
CAUTION: High-Energy Electric Spark!
The CD ignition systems produce a high-energy
electric spark, but the spark must be discharged, or
damage to the system can result. Do not crank or run
an engine with a spark plug lead disconnected. Always
provide a path for the spark to discharge to ground.
Electrical System and Components
Reported ignition problems are most often due to poor
connections. Before beginning the test procedure,
check all external wiring. Be certain all ignition-related
wires are connected, including the spark plug leads.
Be certain all terminal connections fit snugly. Make
sure the ignition switch is in the run position.
NOTE: The CD ignition systems are sensitive to
Test Procedure for Standard (Fixed Timing) CD
Ignition System
Isolate and verify the trouble is within the engine
ignition system.
1. Locate the plug connectors where the wiring
**NOTE: If the engine starts or runs during any of the
2. Test for spark on both cylinders with Kohler
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excessive load on the kill lead. If a customer
complains of hard starting, low power, or
misfire under load, it may be due to excessive
draw on the kill circuit. Perform the
appropriate test procedure.
harnesses from the engine and equipment are
joined. Separate the connectors and remove the
white "kill" lead from the engine connector. Rejoin
the connectors and position or insulate the kill
lead terminal so it cannot touch ground. Try to
start** the engine to verify whether the reported
problem is still present.
a. If the problem is gone, the electrical
system on the unit is suspect. Check the key
switch, wires, connections, safety interlocks,
etc.
b. If the problem persists the condition is
associated with the ignition or electrical
system of the engine. Leave the kill lead
isolated until all testing is completed.
testing, you may need to ground the kill lead
to shut it down. Because you have interrupted
the kill circuit, it may not stop using the
switch.
ignition tester, SPX Part No. KO1046 (formerly
Kohler Part No. 24 455 02-S). Disconnect one
spark plug lead and connect it to the post terminal
of the tester. Connect the clip to a good ground,
not to the spark plug. Crank the engine and
observe the tester spark gap. Repeat the
procedure on the other cylinder. Remember to
reconnect the first spark plug lead.
Section 8
8
8.7