Troubleshooting - Honda VT750C2 Shadow Spirit Service Manual

IGNITION SYSTEM
TROUBLESHOOTING
• Inspect the following before diagnosing the system.
- Faulty spark plug
- Loose spark plug cap or spark plug wire connection
- Water in the spark plug cap (Leaking the ignition coil secondary voltage)
• If there is no spark at either cylinder, temporarily exchange the ignition coil with a known-good one and perform the
spark test. If there is spark, the original ignition coil is faulty.
• "Initial voltage" of the ignition primary coil is the battery voltage with the ignition switch turned to ON and the engine
stop switch at "0". (The engine is not cranked by the starter motor.)
No spark at spark plugs
UNUSUAL CONDITION
PROBABLE CAUSE (Check in numerical order)
Ignition coil
primary volt ­
age
No initial voltage with the ignition
switch turned to ON and the
engine stop switch at "0". (Other
electrical components are nor ­
mal)
1. Faulty engine stop switch.
2. An open circuit in BlackJwhite wire between the ignition
coil and engine stop switch.
3. Loose or poor connection of the primary terminal, or an
open circuit in the primary coil.
4. Faulty rCM (in case when the initial voltage is normal
with the ICM connector disconnected).
1. Incorrect peak voltage adaptor connections. (System is
normal if measured voltage is over the specifications
with reverse connections.)
2. Battery is undercharged. (Voltage drops largely when the
engine is started.)
3. No voltage at the Black wire of the ICM connector, or
loose or poorly connected ICM connector.
4. Loose or poor connection or an open circuit in Blue/
yellow or Yellow/blue wire between the ignition coils and
ICM.
5. A short circuit in the ignition primary coil.
6. Faulty sidestand switch or neutral switch.
7. Loose or poor connection or an open circuit in No.6
related wires.
- Sidestand switch line: Greenlwhite wire
- Neutral switch line: Light green wire
8.
Faulty ignition pulse generator. (Measure peak voltage.)
9.
Faulty ICM (in case when above No.1 through 8 are nor ­
mal).
1. Incorrect peak voltage adaptor connections. (System is
normal if measured voltage is over the specifications
with reverse connections.)
2. Faulty peak voltage adaptor.
3. Faulty ICM (in case when above No.1 and 2 are normal).
1. The miJltimeter impedance is too low; below 10 MQ/DCV.
2. Cranking speed is too slow. (Battery is undercharged.)
3. The sampling timing of the tester and measured pulse
were not synchronized. (System is normal if measured
voltage is over the standard voltage at least once.)
4. Faulty ICM (in case when above No.1 through 3 are nor­
mal).
1, Faulty spark plug or leaking ignition coil secondary cur­
rent ampere.
2. Faulty ignition coil(s).
1. The multimeter impedance is too low; below 10 MQ/DCV.
2. Cranking speed is too slow. (Battery is undercharged.)
3. The sampling timing of the tester and measured pulse
were not synchronized. (System is normal if measured
voltage is over the standard voltage at least once.)
4. Faulty ignition pulse generator (in case when above No.1
through
~
are normal).
1­
Faulty peak voltage adaptor.
2. Faulty ignition pulse generator.
Initial voltage is normal, but it
drops by 2 - 4 V while cranking
the engine.
.
Initial voltage is normal but there
is no peak voltage while cranking
the engine.
Initial voltage is normal but peak
voltage is lower than the standard
value.
Initial and peak voltages are nor­
mal but no spark jumps.
Ignition pulse
generator
Peak voltage is lower than the
standard value.
No peak voltage.