A Better Spark Tester?

For my early 1990's Johnson outboards 6hp, 25hp, and 115hp, I use an adjustable gap spark tester set to 7/16, if it jumps it, then I set it to 3/4 to see if it does it, if it does it is good. I'm told by the forum that the spark must snap and be blue, two things which I have never seen yet. Maybe they are testing them at night (see blue?), and how I'm supposed to hear a snap with the starter turning is a mystery to me. ANYHOW, is this OTC 6589 a more accurate tester, see the review from Amazon posted below.

OTC 6589 Electronic Ignition Spark Tester





http://www.amazon.com/gp/product/B0050SFVO2/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER

Most Helpful Customer Reviews

42 of 46 people found the following review helpfulProfessional Mechanic here
By EAGLESOAR1 on May 7, 2013

Verified Purchase I own an automotive repair facility that employs 3 other technicians and I have been using spark testers for over 30 years and I have tried them all:

1. The plastic encapsulated ones (not reliable or accurate)

2. The "In Line" type - NEVER - NEVER USE THESE!!
It only takes around 10,000 volts to "light" those up - but today's cars need upwards of 50,000 volts so you'll have a "light" but not enough volts to fire the spark plug.

3. I have had 2 OTC 6589's in my box for 20 years - they ALWAYS work AND tell the TRUTH!

Yes, I have played around with the others and ALL OF THE DIFFERENT STYLES OF THE FIRST 2 I LISTED HAVE CAUSED ME TO MISS A DIAGNOSTIC. (Hence - cost me productivity time & money) But, when I am in doubt, I grab my OTC and PROVE IT! I NO LONGER USE OR ALLOW IN THE SHOP ANY OTHER SPARK TESTER THAN AN OTC.

When I am diagnosing a V-6, V-8 or V-10 motor, I use 2 of these at the same time - one on each side of the motor. Sadly, I dropped one and it being porcelain - it broke (just like a regular spark plug would) So I just ordered 2 more today to keep in my shop.
By the way--- the KD 2757 that "LOOKS" the same as the OTC one DOES NOT!!! They changed the design and it is now "plastic encapsulated" and not as accurate. (Same design as the KD 2756)

Yes - the OTC is more expensive but this is truly a case of " YOU GET WHAT YOU PAY FOR!"

Update:
Something I forgot to mention - the clips on these are as heavy duty as they could make them with the amount of material they have to work with.
I don't use the clips on the tester itself (yes, they break)
I use a 3 foot jumper wire I made out of common "lamp cord" with alligator clips on each end. (it's flexible, heavy duty and rated for 25 amps)
(also see: Kastar Hand Tools (KAS1138) 2 x 30' Magnetic Retractable Test Leads - 10 amp rating)

I clip one end of the jumper wire to the spark tester clip and the other end to the CLEAN Negative post on the battery - not any metal on the engine itself.
If you don't "KNOW" that you have a good ground (rust, corrosion, bad ground from battery to engine block) then you could make a false diagnostic not due to the spark tester operation but because you didn't have a good ground path for the current.
Whenever I am testing electrical, I NEVER ground to the frame or body - I always run a jumper wire to the battery negative post - and make sure the negative battery post is clean!

Hmmm....your "testimonial" from the user who "sadly dropped one" seems to be BS to me.

Anyway....here is what I use. I specifically refuse to use on with the clip or clamp soldered to the side of the tester.
There is too much flexing and stress on that point, and the clip always breaks off.

This one avoids that problem, is adjustable, and if you add a small stop nut to the adjusting screw, it will allow locking at 7/16" gap.

http://www.amazon.com/AMPRO-T71240-Energy-Ignition-Tester/dp/B00A8FO87S

I just use a 40 year old tester.----Has 4 wires that slip into the sparkplug boots.----Adjustable gaps in open air and an alligator clip to ground.-----------Most folks are amazed by how simple this spark tester is.------Been asked numerous times " did you make it yourself "--------Works faithfully time after time !!!

racerone said:

I just use a 40 year old tester.----Has 4 wires that slip into the sparkplug boots.----Adjustable gaps in open air and an alligator clip to ground.-----------Most folks are amazed by how simple this spark tester is.------Been asked numerous times " did you make it yourself "--------Works faithfully time after time !!!

Click to expand...

Matter of fact, yes I did make a similar one myself, 60 years ago, and still using it, though it is falling apart.

I might note though that the very fast, very high voltage sparks in todays systems usually are not blue. Your mileage may vary.

You guys see the one that someone posted here a few years back?

Made from a 6 cylinder distributor cap. The center contact in the cap was drilled out and removed. Then a metal disk was fashioned and bolted in where the center contact used to be, with a ground lead coming out the post on the other side of the cap.

The metal disk was made with the diameter being such that the gap between the disk and each individual plug lead contact was 7/16"

Attach ground wire, attach spark plug wires to the dist cap posts, crank starter, and watch the sparks jump from each cylinder post to the center disk.

He had pics up, as well as a video.....looked pretty cool, but I like the simplicity of a single cylinder spark tester, not all 4 (or 2, 3, 6) at once.

With the checker I use you just plug in 2 of the wires for a 2 cylinder engine.-----elegantly simple and " dummy proof " too

A spark gap tester is simple to use. The recommended 7/16" gap has always worked for me on outboard motors. I use mine in line between the spark plug installed normally in the engine and the plug wire. This means that the spark must jump the 7/16" gap and the spark plug gap in the motor while running. You can then also increase engine rpm to verify spark at higher speeds. My experience has shown a strong blue spark with a noticeable popping noise in a healthy ignition. The gap is determined by the amount of voltage generated by the ignition, spark plug gap, and the compression ratio. Most manuals will give an air gap recommendation for a spark test. An air/gas mixture at high pressure creates a much denser gap for the spark to jump then in out in the open. I use one from Auto Zone for about $9.00.

• Ignition Tester
• Great Neck/Adjustable ignition spark tester

Great Neck/Adjustable ignition spark tester





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Part Number: 25069
Alternate Part Number: 64


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I've got the same one Racerone has got and have had it over 40 years. It was built by Stevens Test Equipment in Waukegan IL.

Hi unclebob, I'm trying to diagnose a hesitation and rough idle problem which I suspect has to do with the ignition system. I replaced the standard plugs with low voltage NGK G-Power plugs and that solved about 80% of the problem which made me suspect something upstream in the ignition system. So I bought a spark tester like the one in your picture, set it to 7/16" / 1.1cm and hooked it up in place of the spark plug ( not in-line ) and saw ( at night ) what looked like weak orange sparks on all four cylinders. This is on a 98 model 2-liter car engine with fairly high compression specs ( 210 psi spec, currently about 195 on all four cylinders ) and a waste spark coil pack ( basically there are two coils and each coil fires two cylinders at a time one on the power stroke, the other on the exhaust stroke ).

The reason I'm asking this question is that there seems to be a big debate here on the net about the significance of spark color, with some people saying you need a strongly blue spark, while others say any spark is sufficient, like these guys over at Briggs & Stratton.

So I'm looking for evidence in the form of someone who had a performance problem, saw orange spark, performed a repair like say replacing the ignition coil, alternator, etc... and then that fixed the performance problem with them seeing strong blue spark afterwards. I just can't afford to go on a wild goose chase replacing stuff in the ignition system.

Thanks!

unclebob said:

A spark gap tester is simple to use. The recommended 7/16" gap has always worked for me on outboard motors. I use mine in line between the spark plug installed normally in the engine and the plug wire. This means that the spark must jump the 7/16" gap and the spark plug gap in the motor while running. You can then also increase engine rpm to verify spark at higher speeds. My experience has shown a strong blue spark with a noticeable popping noise in a healthy ignition. The gap is determined by the amount of voltage generated by the ignition, spark plug gap, and the compression ratio. Most manuals will give an air gap recommendation for a spark test. An air/gas mixture at high pressure creates a much denser gap for the spark to jump then in out in the open.

Click to expand...