Spark Test Screwdriver proper use?

[outdoorsman310]

I bought a spark test pocket screwdriver months ago and an old mechanic said it should light up when you put it near a plug wire. It did not light up, then he put it in one of the spark plug boots while holding it as the engine was cranked over. then he and the screwdriver lit up!! I am curious as to how these work and the proper usage. Do they only work on solid (copper) core plug wires? Here is a picture of the type of screwdriver I have:

It says not for electronic ignition on the side. Thanks for reading this even if you know as much about it as me!

 

[zkling]

Try this for your image

 

[outdoorsman310]

Thanks, That is what I was attempting to upload

 

[zkling]

Tip, when you link to an image via the little pop up box, click once, the existing "http" will turn blue then past the image you want to link to. Otherwise you end up with two http's and it will not work.

so my code looks like ["IMG]https://scontent-a-lga.**.fbcdn.net/hphotos-ash3/993746_737290706286588_20341311_n.jpg[/IMG"]
remove "" in the brackets to make it work.

Don't quote me on this, but when I have used those in the past you need an exposed part of the HV circuit, like a wire without a boot, then touch the wire/plug connection with the spark tester. :dunno:

[IMG]https://scontent-a-lga.**.fbcdn.net/hphotos-ash3/993746_737290706286588_20341311_n.jpg

 

[outdoorsman310]

that makes sense. I dont think stray electromagnetic currents would be enough to light it up but I could be wrong

 

[outdoorsman310]

I should have done some testing before asking this. The 1st spark test screwdriver would not light up unless in line with the high voltage. I believe it may have been defective. I tested this on a 99 ds80 and 77 ke250 both dirt bikes with copper ht leads. The tester lit up orange when the screwdriver blade is placed on the plug wire. It seems to work better around connections and closer to the ign coil. I then tested this on a 2000 Honda Accord 2.3L it has a dist and original wires. I am assuming they are not copper. The tester lit up near distributor cap when placed on multiple or individual plug wires. If you disconnect a plug wire from a spark plug and place the test screwdriver around that wire somewhere, the screwdriver will light up brightly and very reliably. So in future testing for spark, I believe it is best to remove the ht lead from spark plugs individually when testing for spark on said cyl to get a reliable and easy reading.

 

[outdoorsman310]

Here is the screwdriver in use!

 

[tradesmanschoice]

They are just neon light bulbs with a series resistor or capacitor built into the screwdriver to limit the current to safe levels.

The current flows from the point you touch at the tip of the screwdriver, through the bulb, through you to ground.

The current level is very low and not harmful, but despite knowing all this, I never trust them and prefer to use a multimeter instead!

Cheers,
Mark.