Loss of spark - magneto? Timing low ohms

Restes · 08-31-2023, 03:17 PM

I went through the common spark trouble shooting 5 pin CDI that you see on here often. TLDR: only measured 16ohms from timing trigger pin to ground, .143 VAC timing trigger on cranking, only seeing fractions of a volt spikes from ignition coil pin to ground.

Here's my results from the diagnostic steps:

5-Pin CDI
The first thing to do is eliminate all kill switches and kill switch wiring:

Method 1) Unplug the CDI and remove the kill switch pin in the CDI connector on the wiring harness. The pin is held in with a spring tab on the pin itself. You'll have to probe into the connector and push this tab in order to extract the pin. Plug the CDI back in (kill switch wire dangling) and see if you have spark. Nope

Method 2) Unplug the CDI. Turn on the ignition switch and set all kill switches to the run position. Use a meter to measure resistance in of the kill switch pin in the wiring harness connector to engine/frame ground. If the resistance is infinite on the 100K ohm scale then your kill switches/kill switch wiring are OK. If you measure zero ohms then you have a kill switch/wiring issue. Was good

The other inputs your CDI needs to make spark are AC Ignition Power, and the Trigger signal. Do the following:

1) Unplug the CDI. In the wiring connector measure the resistance of the AC Ignition Power pin to the Ground pin. You should see 400 ohms or so. What do you measure? 332 ohms

2) Measure the resistance of the Timing/trigger pin to the ground pin. You should measure 150 ohms or so. What do you measure? ONLY 16 OHMS

3) Leave the CDI unplugged. Set your meter to measure AC volts on the 100 volt scale. Measure the voltage on the AC Ignition Power pin to the ground pin while cranking the engine. You should see 40 to 80 volts AC while the engine is cranking. What do you measure? 45v

4) Set your meter to measure AC volts on the lowest scale you have. Ideally this would be 2 volts but many meters don't go down this low. In that case use the lowest scale you have. Measure the voltage on the Timing Trigger pin to the Ground pin while cranking the engine. You should 0.2 t0 0.4 volts AC. What do you measure? ONLY .143v

Now for measuring the output side of the CDI:

A) Leave the CDI unplugged. In the CDI wiring connector measure the resistance of the Ignition Coil pin to the ground pin. You should measure less than 1 ohm (but not zero ohms). What do you measure? 0.6 ohm

B) Plug the CDI back in. Set your meter to measure AC volts on the 20 volt scale. Set all kill switches to the run position. Crank the engine while measuring the voltage on the Igntition Coil pin to ground. Poke through the insulation of the wire if you can't probe the connector.
What you should see is a lot of random numbers with lots of zero values as well. This is because the meter may catch all or part of the spark event voltage, with a lot of nothing in between. Describe what you see. Only a spike of 0.15-0.25v at beginning and end of cranking (I figure this could be a peculiarity of my multimeter)

08-31-2023, 03:17 PM	#1
Restes Join Date: Oct 2022 Posts: 2	Loss of spark - magneto? Timing low ohms I went through the common spark trouble shooting 5 pin CDI that you see on here often. TLDR: only measured 16ohms from timing trigger pin to ground, .143 VAC timing trigger on cranking, only seeing fractions of a volt spikes from ignition coil pin to ground. Here's my results from the diagnostic steps: 5-Pin CDI The first thing to do is eliminate all kill switches and kill switch wiring: Method 1) Unplug the CDI and remove the kill switch pin in the CDI connector on the wiring harness. The pin is held in with a spring tab on the pin itself. You'll have to probe into the connector and push this tab in order to extract the pin. Plug the CDI back in (kill switch wire dangling) and see if you have spark. Nope Method 2) Unplug the CDI. Turn on the ignition switch and set all kill switches to the run position. Use a meter to measure resistance in of the kill switch pin in the wiring harness connector to engine/frame ground. If the resistance is infinite on the 100K ohm scale then your kill switches/kill switch wiring are OK. If you measure zero ohms then you have a kill switch/wiring issue. Was good The other inputs your CDI needs to make spark are AC Ignition Power, and the Trigger signal. Do the following: 1) Unplug the CDI. In the wiring connector measure the resistance of the AC Ignition Power pin to the Ground pin. You should see 400 ohms or so. What do you measure? 332 ohms 2) Measure the resistance of the Timing/trigger pin to the ground pin. You should measure 150 ohms or so. What do you measure? ONLY 16 OHMS 3) Leave the CDI unplugged. Set your meter to measure AC volts on the 100 volt scale. Measure the voltage on the AC Ignition Power pin to the ground pin while cranking the engine. You should see 40 to 80 volts AC while the engine is cranking. What do you measure? 45v 4) Set your meter to measure AC volts on the lowest scale you have. Ideally this would be 2 volts but many meters don't go down this low. In that case use the lowest scale you have. Measure the voltage on the Timing Trigger pin to the Ground pin while cranking the engine. You should 0.2 t0 0.4 volts AC. What do you measure? ONLY .143v Now for measuring the output side of the CDI: A) Leave the CDI unplugged. In the CDI wiring connector measure the resistance of the Ignition Coil pin to the ground pin. You should measure less than 1 ohm (but not zero ohms). What do you measure? 0.6 ohm B) Plug the CDI back in. Set your meter to measure AC volts on the 20 volt scale. Set all kill switches to the run position. Crank the engine while measuring the voltage on the Igntition Coil pin to ground. Poke through the insulation of the wire if you can't probe the connector. What you should see is a lot of random numbers with lots of zero values as well. This is because the meter may catch all or part of the spark event voltage, with a lot of nothing in between. Describe what you see. Only a spike of 0.15-0.25v at beginning and end of cranking (I figure this could be a peculiarity of my multimeter)
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