How to Test a 2-Stroke CDI with Pickup Coil/Stator
Testing a 2-stroke CDI unit and its associated pickup coil/stator requires a methodical approach and some basic testing equipment. A faulty CDI or pickup coil can lead to starting problems, poor engine performance, or even complete engine failure, so accurate diagnosis is crucial. This guide will walk you through the process.
Important Safety Note: Before starting any work on your engine, disconnect the spark plug and battery. Working with electrical components in an internal combustion engine presents a risk of electric shock and injury. Always be cautious.
Tools and Equipment You'll Need:
- Multimeter: A digital multimeter is essential for testing voltage and resistance.
- Ohmmeter (part of the multimeter): Used to measure the resistance of the pickup coil and CDI unit (if applicable).
- Voltmeter (part of the multimeter): Used to check for voltage output from the pickup coil.
- Spark plug tester (optional): Helpful for verifying the CDI's spark output directly.
- Wiring Diagram: A wiring diagram specific to your engine model is crucial for identifying the correct wires and connections. This is often found in your owner's manual or online through engine repair forums.
Step-by-Step Testing Procedure:
1. Visual Inspection:
- Begin by visually inspecting the CDI unit and pickup coil/stator for any obvious signs of damage, such as cracks, burns, or loose connections. Look for corrosion or any signs of water ingress.
2. Testing the Pickup Coil/Stator:
-
Resistance Test: Using the ohmmeter function on your multimeter, measure the resistance of the pickup coil windings. Your wiring diagram will show the terminals you need to test. Compare the measured resistance to the specifications provided in your service manual or online resources for your specific engine model. A significantly higher or lower resistance than specified indicates a problem with the pickup coil.
-
AC Voltage Test: With the engine rotating (cranking it over is best, but be mindful of safety precautions), measure the AC voltage output from the pickup coil using the voltmeter function of your multimeter. You'll need to connect the multimeter leads to the pickup coil terminals according to the wiring diagram. A weak or absent AC voltage signal suggests a problem with the pickup coil or the stator's magnets.
3. Testing the CDI Unit:
Testing the CDI unit directly can be more complex, and the method varies depending on the CDI's design. Some CDI units have internal components that are not easily testable with basic equipment.
-
Resistance Test (if applicable): Some CDI units can be tested for internal resistance, but only if the manufacturer provides specific resistance values. Consult your service manual.
-
Visual Inspection: Examine the CDI unit for any signs of damage, such as burned components or cracks.
-
Spark Test (Indirect Method): If you have a functioning pickup coil, you can indirectly test the CDI by checking if it generates a spark. Connect the spark plug wire to the spark plug and a ground (e.g., engine block). While cranking the engine, observe if the spark plug fires. If not, the CDI unit is likely faulty. A spark plug tester can help visualize this test.
4. Interpreting the Results:
-
If the pickup coil tests show abnormal resistance or low/no voltage output, it needs replacing.
-
If the CDI unit fails the spark test (or shows abnormal resistance if applicable), it needs replacing.
-
If both the pickup coil and CDI test within acceptable ranges but there's still no spark, the problem might lie elsewhere in the ignition system (e.g., wiring harness, kill switch, etc.)
Troubleshooting Tips:
- Consult your engine's service manual: This is invaluable for obtaining specific resistance and voltage values for your components.
- Check your connections: Loose or corroded connections can cause intermittent problems.
- Replace parts in stages: If multiple components are suspect, replace one at a time to pinpoint the faulty part.
This guide provides a general overview of how to test a 2-stroke CDI and pickup coil. Always refer to your specific engine's service manual for detailed testing procedures and specifications. Remember safety first – disconnect the battery and spark plug before commencing any tests.
