Ignition System Troubleshooting - Yamaha MM700A Manual

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IGNITION SYSTEM TROUBLESHOOTING

All models are equipped with a capacitor discharge ig-
nition system. This solid state system uses no contact
breaker point or other moving parts. Because of the solid
state design, problems with the capacitor discharge sys-
tem are relatively few. Most problems fall under the cate-
gories of no spark or weak spark. These two conditions
are relatively easy to diagnose. However, intermittent
problems that occur due to a vibration, or only when the
engine is hot or under a load can be difficult to diagnose.
Refer to Figure 2 for general troubleshooting proce-
dures.
Test Equipment
Use a digital multimeter for accurate testing of the igni-
tion system. If a multitester is not available, use visual in-
spection and an ohmmeter to pinpoint electrical problems
caused by dirty or damaged connectors, faulty or dam-
aged wiring or electrical components that may have
cracked or broken. If basic checks fail to locate the prob-
lem, take the snowmobile to a Yamaha dealership and
have them troubleshoot the electrical system.
Ohmmeter readings should be made when the engine is
cold. Readings taken on a hot engine shows increased re-
sistance caused by engine heat and result in unnecessary
parts replacement without solving the basic problem.
Precautions
Certain measures must be taken to protect the capacitor
discharge system. Damage to the semiconductors in the
system may occur if the following is not observed.
1. Do not attempt to start the engine or rotate the crank-
shaft if the CDI unit is not grounded to the engine.
2. Do not touch or disconnect any ignition components
when the engine is running or while the battery cables are
connected (if so equipped).
and tight. Make sure the wiring connectors are pushed to-
gether firmly.
Troubleshooting Preparation
NOTE
To test the wiring harness for poor connec-
tions in Step 1, bend the molded rubber con-
nector while checking each wire for
resistance.
COMPRESSION
SPARK
Refer to the wiring diagrams at the end of this book
when performing the following.
1. Check the wiring harness for damage.
2. Check all the connectors as follows:
a. Disconnect each electrical connector in the ignition
circuit. Check for bent or damaged terminals in
each male connector (Figure 3). A bent terminal
does not connect to its mating receptacle in the fe-
male end of the connector. This causes an open cir-
cuit.
b. Check each female connector end. Make sure the
metal terminal on the end of each wire (Figure 4) is
pushed all the way into the plastic connector. If not,
carefully push them in with a narrow-blade screw-
driver. Make sure to not pinch or cut the wire.
CHAPTER TWO