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Old 02-19-2017, 02:48 PM   #1
36tudordeluxe
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Default Test light to confirm spark to plug?

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?
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Old 02-19-2017, 02:53 PM   #2
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Default Re: Test light to confirm spark to plug?

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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Old 02-19-2017, 02:59 PM   #3
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Default Re: Test light to confirm spark to plug?

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Originally Posted by AnthonyG View Post
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.
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.
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Old 02-19-2017, 02:59 PM   #4
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Default Re: Test light to confirm spark to plug?

I don't think turning the engine over by hand will give you a strong enough spark to detect. Try it with engine running.
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Old 02-19-2017, 03:01 PM   #5
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Default Re: Test light to confirm spark to plug?

What kind of test lite?

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Old 02-19-2017, 03:13 PM   #6
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Default Re: Test light to confirm spark to plug?

If it was a 12 Volt test light you would think 10,000 volts would light it.

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Old 02-19-2017, 03:30 PM   #7
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Default Re: Test light to confirm spark to plug?

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
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Old 02-19-2017, 03:35 PM   #8
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Default Re: Test light to confirm spark to plug?

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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File Type: pdf Test light.pdf (103.5 KB, 28 views)

Last edited by 36tudordeluxe; 02-19-2017 at 04:09 PM.
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Old 02-19-2017, 05:22 PM   #9
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Default Re: Test light to confirm spark to plug?

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?
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Old 02-19-2017, 05:27 PM   #10
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Default Re: Test light to confirm spark to plug?

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.
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Old 02-19-2017, 05:32 PM   #11
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Default Re: Test light to confirm spark to plug?

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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Old 02-19-2017, 05:37 PM   #12
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Default Re: Test light to confirm spark to plug?

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.
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Old 02-19-2017, 05:45 PM   #13
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Default Re: Test light to confirm spark to plug?

That'll work, too! DD
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Old 02-19-2017, 05:53 PM   #14
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Default Re: Test light to confirm spark to plug?

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.
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Old 02-19-2017, 06:28 PM   #15
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Default Re: Test light to confirm spark to plug?

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Originally Posted by V8COOPMAN View Post
I believe VWs were NEG ground. Soooo......that will relate to your POS post on your POS GROUNDED 6v system. DD
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?
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Old 02-19-2017, 07:05 PM   #16
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Default Re: Test light to confirm spark to plug?

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
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Old 02-19-2017, 07:13 PM   #17
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Default Re: Test light to confirm spark to plug?

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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Old 02-19-2017, 08:02 PM   #18
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Default Re: Test light to confirm spark to plug?

Quote:
Originally Posted by V8COOPMAN View Post
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
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.
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Old 02-20-2017, 12:24 AM   #19
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Default Re: Test light to confirm spark to plug?

Spark Test Light - in series with coil or sparkplugs. No ground.

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Old 02-20-2017, 06:12 AM   #20
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Default Re: Test light to confirm spark to plug?

I have a spark tester from the 70's from champion, its a pen type that flashes. This has been useful finding bad plugs or wires .

https://www.google.com/imgres?imgurl...act=mrc&uact=8
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