How To Test Spark Plug Wires 

When measuring the wire's resistance, your fingers will not affect the reading(unless your fingers are DAMP/WET). When measuring resistance levels above 100,000 ohms, never use your fingers. You will get incorrect readings.

The most calm, logical, step by step, video ive seen on this subject. The same goes for the spark plug video

I find your tutorials very relaxing, and informative to watch. Today you taught me something new; using the screwdriver dragging along the s.plug wire. Thank you. Your videos are much appreciated!! All the best from New Rochelle N.Y.

Great video. I recently had issues with the plastic cracking on very old wires causing arcing!

Thanks for the interesting videos.Have a nice christmas.

Good video, That is how we used to test them years ago when I started my apprenticeship......thanks for sharing......Memories...... Neal

Excellent tutorial !!! Allow my two cents? Dielectric (insulation) failure happens to not only plug wires, I have seen distributor caps, plug connector ends that are of an insulating material and the ignition coil tower break down. These items have essentially become electrically porous. Salt water spray and hydrocarbons exacerbate this issue. On GM distributor caps with the ignition coil inside the cap, a bad conductor within the plug wire could actually burn back along the wires core, getting wider with every spark. This eventually would leave the coil/cap with a flash over condition that would arc through to the grounded coil mounting screws and or an adjacent plug terminal. The cause of the bad wire usually was due to a failed attempt to remove the sparkplug boot and pulling instead on the wire, streaching it and breaking the carbon impregnated core fibers. All secondary voltage ignition related issues can leave behind a high voltage conducting carbon tracking that may not be visible, although sometimes it will appear as a black crack or trail. Obvious signs of a spark plug wire having been burned or chafed is suspect and should be replaced. Other factors such as environmental degradation via ozone or in the case of recessed plugs down within the valve cover where the engine oil can accumulate, will most assuredly cause that wire and insulator to fail over permanently. I recall a arc faulted distributor rotor that had me going crazy until I tracked that down, the high voltage went in but never came out... LOL There used to be high pot testers to check for these types of conditions. ;>) Some notes on the low voltage side of ignition systems... Some really old, post points and condenser cars (Late 70's Toyota) they had an ignition module but still used conventional hard switching via a set of contact points. These cars had a nylon feed through terminal block that held a screw and nut, the nylon could crack and although the measured voltage was normal voltage, the switched signal would be lost due to dampness in the crack leaving the ignition module (Amplifier) without anything to do. Do not get a false feeling of bravado when dealing with the low voltage side of the ignition coil, not only do they spike to hundreds of volts, but if coupled to a solid state ignition module, they can fail when damp. This also causes the magneto grounding circuits on many air cooled engines, issues with a "No spark" problem. This is the circuit that allows the throttle to turn off the engine. Check for cracked plastic on the coil negative terminal wiring ! For anyone dealing with the traditional contact "points and condenser" (capacitor) ignition be aware that the condenser often does fail in due time, causing severe pitting of the electrical contacts. That capacitor is in fact part of a tuned circuit with the ignition coil that when properly matched helps in keeping the points contacts from arcing. Good luck with ignition related trouble shooting!!!

informative, thank you...

Excellent video, thank you for sharing

I LOVE WATCHING YOUR VIDEO'S,VERY WELL EXPLAINED.

Thanks. I realised today one of my 883 hugger Harley cables is badly corroded around crimp at plug end....safe to say need to get swapped out ? Plugs look ok... getting really low power

very good tips thanks. *****

Just like that I'm a subscriber, great video.

Excellent. Thank you for such detailed explanations. Also, I like your spray bottle @ 8:01. What's that from? I will buy it just for the bottle.

OLD SCHOOL , but VERY effective !

Hi just like to know my spark plugs wires has a reading one and the other three have nothing, do I replace the wires?

Is there information printed on the wire which would indicate if the wire is of the resistive type and or the value of it's resistance. Also, can we just do an insulation test using a Mega meter? We use this method to test cables on ships, setting the meter on the 500 volt range. however, would such a test be inadequate for spark plug wires because of the higher voltages encountered? thank you and have a jolly good day or night as the case may be when you finally read this comment.

I LOVE YOU!!! I just cut a wire as the cap was so tight I needed to grip it with pliers and lever it off with a large screw driver. One out of 8 slipped and the screw driver went straight through the wire.. I'm now going to go repair it thanks to this vid!! Thanks!! Oh just one quick question I have a spare wire at 1800 ohms.. all the rest are 800 (they are very short).. If I can't make the fixed one reach should just plugging the 1800 wire in cause any real problems? Thanks :)

nice job

Thanks ! I tried the test for ohm. Then i went for bip sound test for wires with résistance measured. But i heard nothing. Why ?

i just spark them across a battery ....from i get a spark ....i'm good .... the mist of water works with out the "probe" bost of the time ....but the vdo it great & informative

How about the readings on plug wires for a v twin Harley engine I have electronic ignition and screaming eagle wires on my bike I checked them with a multimeter the long wire to the front cylinder reads around 5,000 and the short around 2,000 I wonder if that's normal? The long wire is 19 inches and the short is 7 inches long.

Can you use this same process to check if an ignition coil for a small engine is working properly?

I think there is a 5th wire on a 4 cylinder car that goes from the coil to the distributor cap. Should that one be tested too?

The screwdriver test sounds good. I had wires that didn't even need a test, just pop the hood open at night and you could see the sparks arcing to ground. I even placed my figures on the wires and watched the sparks jump to my hand without a nasty shock. Most generally though, those are the cheap crapy wires that do that. I no longer buy cheap wires since then, their not even worth the time to put em on.

hi im wanting to buy a set af msd plug wires but cant find the right wires 4 my vehicle. so im thinking perhaps they may b universal. my vehicle is a gm 3800 supercharged l67 v6. your help would b appreciated.

thanks very informative and comprehensive explanation. can i use test light rather than screwdriver one end be connected to negative and other end pass it over wire if it come cross the spark it would light up.would this work?

Clever!

nice video . my multimeter has a continuity beeper however it won't beep on a known good wire why is that?

I was once told that you need resistor plugs or resistor wires, but not necessarily both. What's your take on that?

If you have a metal loop held on silocon you'll have false signal issue

Some spark plug leads like in the 80s Mercedes use solid copper core leads but with resistors built into the plug caps, this basically means all the leads should have the same resistance.

Graphite on the sticky note....ingenious

The third type are (higher quality) solid wire with resistors in the boots.

You mentioned that "the purpose of the graphite is to add resistance to this wire." Does it not add continuity rather than resistance? If there was no graphite added to the fiberglass core, would it conduct electricity quite well, or not at all? I would think not at all. When you measured the resistance of the pencil line, you were actually measuring the increasing resistance of a longer, and not very good conductor.

How do I view all your other videos

Well obviously if putting them back in different spots makes it misfire. Thier prob bad. Now if your talking about mixing up firing order. That makes sense

you are the mother fucking man thank you for all of the information

What about is not reading

what??

Always position camera so that light source (especially windows, etc) are *behind* the camera. That way you don’t have hard-to-see meter displays, etc. Subject 👍🏻Video quality 👎🏻

Nah, you're doing it all wrong. Just pull the wire off your plug, then get your cousin Billy Bob to stick his finger into the plug wire where the plug goes. Once you are sure cousin Billy Bob has his finger in the right place, go turn the engine over a few times with the key switch. If cousin Billy Bob flops around like a fish, then the wire is good. If he just stands there blinking his eyes at you slowly, then the wire is bad.... This way of testing plug wires is much more fun, but if cousin Billy Bob is very bright you may need a few more cousins to be able to test all of your wires.