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How to test ignition spark with a Mac Tools Ignition Spark Tester

How 2 Wrench

67,226 views

How to test spark with a tester.
It breaks my heart to announce this but the program lost funding and is now closed. Many great years there. You can continue to follow Shane's work on the ‪@How2Wrench‬ channel!
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20 Comments

@chvydrptop 9 years ago

FYI - Mac doesn't make this tool its relabeled from Lisle. A lot of of tools are just relabels. Lisle 20700.

@jab5385 4 years ago

The Gap setting is for checking how good the Coil is the numbers are foe KV ( Killer Volts ) the lower the number the weaker the coil, a good coil should read 30, to 40,000 KV it's a good tester to see how good the coil is.

@jacquelinem2873 4 years ago

On the last tester, open spark one…the SE means small engine. The 20,30,40 is on kilovolts…most cars are 20-30….some ecoils in some modern cars are 30-60. Set the tip to the number.

@spelunkerd 11 years ago

Love these videos, Shane.
The gap will be different if you keep the plug inline, since in that situation you are jumping across two gaps. Voltage drop across the spark plug (in series) should result in lower voltage drop across the tester. I really like that style of tester because you don't need to remove the plug, so you get the test done in half the time.

@projector7141 3 years ago

I wish these things came with a proper scale. The markings are not quite in kV as you see on all these videos and websites. A 10 mm air gap in dry air between tips is about 30kV, increasing almost linearly. But it varies with humidity. At about 60% relative humidity, it is only 8 kV per 10 mm. If your compression ratio is 10:1 that means if your spark jumps 10 mm on the tool, it can jump about 1 mm of plug gap under compression, or more likely 0.8 mm because of the fuel vapour. I hope this comes in handy for people testing coils and remember to keep your hands clear because the sparks are pulsed and high voltage. Also check the zero on your tool.

@jimmiddleton8171 7 years ago

On some of these testers they are marked in KV (Kilovolts), 10, 20, 30,40 etc. as you adjust the gap.

@lauraw3923 9 years ago

Thanks. I tell our customers all the time the plug on the engine is not a valid way to check for spark. Looks like you've got a great program.

@angleturner 5 months ago

MAC price $21.
Amazon price $4.16, same exact unit.
The SE stands for small engine,
The 10,20,30 is how many KV the coil is putting out.

@charleshall5576 10 years ago

Shane, I love these videos but it is not really the compression that would prevent spark but the density of the fuel/air mixture caused by the compression that would prevent a weak ignition system from being able to spark across the gap. The thing to think about is as you compress a fuel/air mixture you increase the density of the medium so it takes a greater amount of energy to spark across the gap.

@Smith93646 2 years ago (edited)

You could have got that same adjustable spark tester from advance auto for $15... Great video

@al1947-m9o 10 years ago

I looked up the part number and can't find it, has it been discontinued? Thanks

@How2Wrench Creator 4 years ago (edited)

Our latest tester that replaced everything we use is from @spark plug testing kit https://youtu.be/h5B0GSY9Ps0

@wiggybends3632 3 years ago

Good vid

@loug4626 5 years ago

Novice here. Can I attach the spark tester as you indicated but grounded to spark plug and actually run the motor ie outboard to determine spark and also increase gap as want to ensure all ignition coils on outboard are at full strength. Thank you and enjoyed your video as very informative in the use of the Mac ignition tester.
Lou

@tamarabarnett9869 1 year ago

❤❤❤

@sparkplugtestingkit 6 years ago

These “types” of spark testers are all over the internet. The reason we invented our “Spark Plug Testing Kit”, was because these “types” of spark testers can give a false positive. It happened to us on a chainsaw that wouldn’t start! These “types” of testers can still light up with a weak spark not strong enough to start an engine. Leading you to believe the fault lies elsewhere. You can find independent videos on YouTube to verify this fact! U.S Patent No. 10,113,527 - A Spark Plug Testing Kit

@RichieRich845 3 years ago

All that you are testing is the coil not the spark plug or the spark plug under pressure. You still don't know what what the spark looks like at the spark plug.

@craigmonteforte1478 5 years ago

Here is a funny a Uncle of mine told me years ago he grew up in a very Rural Louisianna in the 1950s and 60s and they had a neighborhood Bully that harassed everyone one day they convinced that kid that if he Urinated on the sparkmPlu it would shut the Lawnmower off when the kid did it he rolled around in the dirt and his Urine puddle holding his Junk and Screaming with his pants down it hurts it hurts my Uncle and his Buddies just all laughed as they knew they got the kid good I’ve been a Gear Head most of my life and like most I’ve been hit with a coil or Spark Plug shock a few times it’s high Voltage but low Amperage so it just makes you jump very quickly but doesn’t have what it takes to kill you although who knows if you have a bad heart or a Pacemaker maybe it could ? I’ve also owned many boats in my life and got hit wit that Voltage down in the bridges working on a engine

@outboardcentral 4 years ago (edited)

The S E means small engine on that tester and good fire should jump that gap. These are great...unless you are working outside in the sun...then you may need to work at night....

@fireburst102 4 years ago

Today I just had an incident where cylinder 4 on my tractor was not firing, but my inline spark tester said I was getting spark there. So I threw on a glove, and unplugged the #4 cylinder spark plug wire, and the sound didn’t change. Pulled the plug out and tested the spark plug with my volt meter, and found continuity between the positive electrode and the threads of the spark plug. Put a new plug in, and we were good to go. So I got a false reading from my inline test light.