IGNITION TROUBLESHOOTING GUIDE: NO SPARK?

Having a hard time finding where you're loosing spark? Look here for a detailed explanation of the entire Yerf Dog GX150 GY6 150cc ignition system.

Ignition Troubleshooting Guide: No Spark?


LAST UPDATED: 09/09/2010

See Attachment: Yerf Dog GX150 Wiring Diagram

To accurately diagnose your ignition system, you will need to do each of these steps in sequence. Start with step 1 and work through this guide completely. If you need assistance contact us with the voltages you see at each step.

This guide is specifically written for the Yerf-Dog GX150, but applies to almost any of the 150cc buggy scooters or ATV's with the standard "AC" CDI setup.

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The 150cc GY6 ignition system is fairly easy to troubleshoot in the case of malfunction. There are 6 major components that work together to produce spark, if any of these is defective, spark will be lost. What we will be doing here is troubleshooting these ignition parts.

Ignition energy travels along the following path starting at the stator:

--1. Stator (6th winding and trigger pickup module)
-----1a. Trigger wire (pickup module)
--2. CDI unit
----- 2a. On/Off ignition switch
--3. Ignition coil
--4. Spark plug

1. Stator (6th winding) -- Directly supplies CDI with power. This 6th winding is dedicated solely to providing energy to the CDI. It is easily distinguished from the other windings as it is the only one covered in white wrapping.

1a. Trigger wire (pickup module) -- A simple type of crankshaft position sensor. Sends a signal to the CDI to let it know when to energize the ignition coil.

Troubleshooting #1 and #1a:
- Set your multimeter to read in VOLTS "AC".
- Locate and disconnect the Black/Red and Blue/Yellow wires coming from the stator, where they plug into the main engine harness.
- While cranking the engine, use a multimeter to check for voltage coming from the Red/Black (CDI power wire) and the Blue/Yellow (trigger wire) coming from stator. Place ground lead of multimeter on a metal surface of the engine while using the red lead on the tips of the wires.
- There should be between 50vAC ~ 100vAC coming from the CDI power wire (Black/Red), although much lower voltages will still be able to produce spark.
- There should be at least 0.05vAC coming from the trigger wire (Blue/Yellow).
- Write the voltages down and continue to the next step.

2. CDI Unit -- The CDI unit is powered by the AC current coming from the 6th stator winding. This current is stored in a capacitor within the CDI unit. When a signal is received from the trigger wire pickup passing over the flywheel magnet, the CDI will discharge the stored energy into the wires leading to the ignition coil.

Troubleshooting #2: At this stage, two parts could be causing lack of spark -- the CDI or the Ignition Kill Switch. We"ll start with the CDI.
- Ensure your multimeter is set to read in VOLTS "AC".
- Just like before: while cranking the engine, use a multimeter to check for voltage at the two primary wires of the ignition coil. Connect your back multimeter lead to the black ground wire at the coil, and with the red lead to the lighter color wire (usually blue or purple, but it varies). At this step we are checking to see exactly what the CDI is outputting. Write the voltages down and continue to the next step.
Next, with the green ignition kill switch in the ON position check for continuity from the green CDI wire, to ground. If there IS continuity: the ignition kill switch is likely bad. Confirm this by disconnecting the switch altogether and try to start the engine. If it starts, you have found the problem.

3. Ignition Coil -- The function of the ignition coil is to step up the voltage of the power supplied from the CDI, and to send the stepped-up power to the spark plug.

Troubleshooting #3: Check for 0.1 ohm ~ 1.0 ohm across the two primary coil terminals. This isn't exactly definitive, as we have seen working coils with 0.0ohms resistance. The best way to tell if the coil is bad is to perform steps 1 and 2. If there is still no spark, the coil is likely bad.

4. Spark Plug -- If the plug is fouled or cracked it may not spark.
Troubleshooting: Replace the spark plug.