Test light to confirm spark to plug?

36tudordeluxe

36tudordeluxe

Well-known member
To confirm spark going to the plug I attached one end of test light to the plug wire and other end to ground, with ignition on rotated engine several times by hand and light never came on. What am I doing wrong?
 
Sounds like no ignition. Was your ignition Switch on? All its gonna show is whether any electric going to spark plug. Won't give any indication of intensity of spark.
 
AnthonyG said:
Sounds like no ignition. Was your ignition Switch on? All its gonna show is whether any electric going to spark plug. Won't give any indication of intensity of spark.
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Yes, ignition is on and have established power to the coil, have tried another cylinder and light still won't come on, the engine runs fine. Not interested in intensity, trying to see when the light comes on before TDC.
 
I don't think turning the engine over by hand will give you a strong enough spark to detect. Try it with engine running.
 
Apples to oranges i guess. Secondary spark at the plug is maybe 8-10,000 volts and last approx 2 miliseconds. Two things , you would need to blink really fast AND the flash would be really really bright !!!!!!!!!!!!!!!!!
The secondary is a open circuit due to rotor and plug gap . A timing light would be the correct tool to be used here, watching the flash on the timing pin.....

You need to listen to my training video on the subject :

https://www.youtube.com/watch?v=AkNsa0BK7Zw
 
Okay, will try timing light. I used the 12V test light on VW Bug engine to see when timing light came on with my degreed crank pulley. Sorry about the uploaded file, didn't mean to send that one but couldn't delete it.
 

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Went back to Volkswagen manual for Dummies and shows test light connection to negative post on coil other end to ground and then get TDC for #1 and rotate distributor to time it. On my '36 engine there's no negative post for the coil, what I'm trying to do is to see when light comes on for #1. Can this test light be used on my '36 engine?
 
You need the right type of light bulb, you need a gas filled neon lamp connected to the spark plug and it will blink if you have spark.
 
I believe VWs were NEG ground. Soooo......that will relate to your POS post on your POS GROUNDED 6v system. DD
 
If you have a distributor-mounted coil, the positive post is in the distributor. If you have an amp meter you can put it on the wire to the coil, when there is amperage the points are closed, when they break for the plug to fire the amperage will go away.
 
My kid brought home a test light awhile ago. Pull the plug wire and snap the wire of the light onto the plug and snap the wire onto the other end of the light. An inline test light. Had the chance to use it once and it worked fine.
 
V8COOPMAN said:
I believe VWs were NEG ground. Soooo......that will relate to your POS post on your POS GROUNDED 6v system. DD
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When I put one lead from the light to terminal post on coil and other lead to ground with ignition on light comes on. So why doesn't light come on with one lead to ground and other lead to #1 plug and plug wire after rotating engine several times past TDC for #1? Am I not doing what post 12 suggests but with a light instead of multi meter?
 
With one lead to the terminal on coil, and the other lead to ground, the light comes on because it is showing that voltage from the ignition switch (ON) is flowing through your test light, to ground!

Remember what Jim (Bubba) said earlier. When you try to hook-up your circuit tester to a plug, it ain't gonna show, because you really don't have a true, conductor circuit. Like he said, the impulse must be several thousand volts to JUMP across the OPEN gaps between the rotor and cap, and then again at the gap between the plug core and the ground electrode. That is inductance, not a true, closed circuit. DD
 
You were trying to adjust valves yesterday. You made reference to TDC, which several of us told you was an acceptable way to adjust your valves, as long as it is TDC on the compression stroke. Is this why you're trying to find when the plug fires? If so, all you have to do to find the correct TDC (compression stroke) is to remove #1 plug and rotate the crank toward #1 coming up to TDC. If you hold your finger over the spark plug hole and feel compression (pressure) on your finger as you turn the crank, you are on the correct TDC to start your valve adjusting when the piston is at TDC. Now, just follow the firing order. Hope this helps. DD
 
V8COOPMAN said:
You were trying to adjust valves yesterday. You made reference to TDC, which several of us told you was an acceptable way to adjust your valves, as long as it is TDC on the compression stroke. Is this why you're trying to find when the plug fires? If so, all you have to do to find the correct TDC (compression stroke) is to remove #1 plug and rotate the crank toward #1 coming up to TDC. If you hold your finger over the spark plug hole and feel compression (pressure) on your finger as you turn the crank, you are on the correct TDC to start your valve adjusting when the piston is at TDC. Now, just follow the firing order. Hope this helps. DD
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Yup, that's exactly what I'm trying to do, was going to use test light to confirm thumb method. Never could get the test light on but can see voltage fluctuation in my meter.
Appreciate all the help guys.
 
Spark Test Light - in series with coil or sparkplugs. No ground.
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