Balif, whack his multi-meter!
Spark plugs
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mike mcs repair
Registered User
chugiak AK
he has a legitimate question here...
as they say use a low voltage one(when measuring resistance mode)...
I have no idea which mine are, but intend to find out...
spark plug ohm meter
As long as you are going to buy a multimeter, might as well get one that reads DC amps like the one Mike suggests. Very good for troubleshooting electrical systems. Most multimeters do not work on dc amps. One that works for both ac and dc is harder to find but generally doesn't cost any more.
As long as you are going to buy a multimeter, might as well get one that reads DC amps like the one Mike suggests. Very good for troubleshooting electrical systems. Most multimeters do not work on dc amps. One that works for both ac and dc is harder to find but generally doesn't cost any more.
wireweinie
FOUNDER
Palmer, AK
A good general purpose meter is a Fluke 114. If you don't like that one just get another. As long as it says 'Fluke'.
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gdafoe
FRIEND
Castle Well Airpark SE of Wickenburg AZ
There was a thread a while back about good old time avionics beech technicians. I know two very good ones personally. Fairly often, when I go into the shop I find myself chuckling because there he is deep into some avionics something or other troubleshooting with the multimeter he picked up free from Harbor Freight. Over on the other bench is a Fluke that is always kept with certification up to date. Point is you don't really have to have a Fluke to test the plugs just go pick up the free one it will read the same.
https://www.aircraftspruce.com/cata...MI-_2w14qu4QIVlLXACh2Zbwq_EAQYASABEgIg0fD_BwE Ohm meter, not a multimeter. difference.
G44
MEMBER
SW Michigan
I have one of these units and use it every time the plugs are out, cheap and easy.
txpacer
SPONSOR
Iowa Park, TX
Apparently, Fluke has outsourced some of the lower end meters. They get mixed reviews.
wireweinie
FOUNDER
Palmer, AK
Depends on what you're trouble shooting. A good quality digital meter uses a very low voltage/current signal when set on the resistance scales (ohms). They also use very little power from the circuit when measuring voltage or current. This is extremely important when troubleshooting, especially with more and more semi conductors being used in all systems.
The flip side to this is the cheaper meters such as most 'analog' meters with a physical needle and scale. Even the higher quality ones such as the Simpson line use higher signals on all settings.
There are advantages to both actually. Digital meters are accurate in the extreme. Even non certified models will measure to tenths of a volt and less than one ohm resistance. Most of them will have an amps scale and a milliamps scale. And the low signal/power loss from the meter helps this. For example, measuring voltage means that you place the meter leads in parallel with the component. A meter that draws a larger amount of power from that circuit will alter the current flow/voltage only while making the measurement, there by giving an incorrect reading.
When testing items such as transistors or items such as switches or breakers, the larger power requirements for an analog meter can be an advantage. This meter can function test transistors and SCRs just by powering them while set on the resistance scale (*don't try this on low power transistors!*). And when testing switches (when removed from the circuit) the higher current flow from the analog meter can sometimes show low resistances better.
While they each have good points, a good quality digital meter will be the best bang for the buck. If you just need the occasional meter, it's especially good as you won't need to second guess yourself every time you use it.
'WE NOW RETURN YOU TO THE PREVIOUS PROGRAM'
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Steve Pierce
BENEFACTOR
Graham, TX
Using the rotation sequence Champion and probably Tempest recommends the fine wires should last to TBO and not foul. Massive electrodes normally wear beyond my no go gauge in 500 hours and do seem to foul more. In my opinion it is a pay now or pay later.
mike mcs repair
Registered User
chugiak AK
it dosen't matter... it's in the happy RANGE
Steve Pierce
BENEFACTOR
Graham, TX
I set them to .016" because everything I maintain is a long way from me and I am usually not going to see it for a year and I want the gap to be at the smallest so it doesn't get to wide and won't start by the time I see it again.
On a Saturday morning a guy flew over to eat at our Dairy Queen and couldn't get the airplane started. Come to find out it was a flight school airplane, had just come out of inspection and he owned the school. Gap was way to wide, regapped and sent him on his way. He got an ear full from me because I had helped several of his stranded students for similar issues and the school would not pay. Finally had to tell the student to call their flight school, I couldn't help them. That all stopped after 9/11.
On a Saturday morning a guy flew over to eat at our Dairy Queen and couldn't get the airplane started. Come to find out it was a flight school airplane, had just come out of inspection and he owned the school. Gap was way to wide, regapped and sent him on his way. He got an ear full from me because I had helped several of his stranded students for similar issues and the school would not pay. Finally had to tell the student to call their flight school, I couldn't help them. That all stopped after 9/11.
Livin' in the past?
You should mention Starbucks and Apple in there. Internetters love to hate the big guys.
Or have the supply house give you the wrong ones and don't notice until after you open them ALL.
Tim
FRIEND
Petersburgh, NY
I use Denso IK-27 fine wire plugs for my mag. And my P Mag. About $4 a piece they last forever. For what it's worth
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Dave Calkins
Registered User
Anchorage, Alaska
tempest makes a slick tester.
holding multimeter probes and a spark plug at the same time was a pain so I built a little fixture the plug fits on and I can "ohm" away
bougjt the tempest tester as soon as I saw it! about a hundred bucks
holding multimeter probes and a spark plug at the same time was a pain so I built a little fixture the plug fits on and I can "ohm" away
bougjt the tempest tester as soon as I saw it! about a hundred bucks
G44
MEMBER
SW Michigan
wireweinie
FOUNDER
Palmer, AK
Come work for me for a day, lol. Your money but I'm not dropping a hundred bucks on something that I can do with a tool that I already own and use daily.
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Dave Calkins
Registered User
Anchorage, Alaska
my thoughts until I saw the Tempest tool
The fixture I made still works great also
The fixture I made still works great also
Well here is the Mil-spec for those who want it, and Massive plugs are designed to last 4-500 hours on average, fine wires are 1800-2200 hours. So you can pay 3 times as much to get a plug that lasts 4 times as long if you get fine wires. Also Champion does not follow the Mil-spec criteria for their plug testing so they don't advocate the 5K ohm resistance as demonstration for a good plug. From what I have found, high resistance = high mag temps. I also use a fluke 114 meter, it does meet the mil-std for most applications except ordnance testing. I don't expect many on here to be testing blasting cap circuits.
It is funny to watch an owner's eyes when you ohm a plug and it is high and I take it gently over to the bench, place a rag over it and smash it with a 3lb hammer, that way it never goes back into the airplane...because if they cant afford a replacement plug, they shouldn't be flying..
spark plug criteria
Stolen from QAA
Background
Discussion about the “right” way to check spark plug resistance can go on until the cows come home. While what happens when 10,000 volts is forced across a resistor under laboratory conditions is interesting, it is hardly relevant to resolving the problems faced by IAs, A&Ps and AEs. The question is; “What’s causing the rough running engine and how can we fix it?” Conditions on a blazing hot or freezing cold ramp aren’t laboratory conditions. What we, as aircraft technicians, need is a useful available tool to identify a spark plug that might be causing a rough running engine.
Military Specification MIL-S-7886 provides guidance for aviation spark plug manufacturers. It addresses checking spark plug resistance using a low voltage ohmmeter. Hundreds of millions of spark plugs later it’s safe to say that the MIL Spec’s advice is good. A typical low voltage ohm meter (or the Tempest AT-5k meter which relies on a low voltage circuit) can help identify suspect plugs. Although many volt meters use nine volts batteries, that’s close enough. The “low voltage” referred to doesn’t hinge on exactly 8 or 10 volts. It addresses the difference between a “megger” or high voltage resistance check, say 500 to 1000 or more volts, and a typical shop floor meter’s use.
Resistance checks DO NOT replace the familiar spark plug cleaner/pressure bomb test box that actually sparks the plugs under air pressure. However, the pressure bomb doesn’t check resistance, and as we know from experience, sometimes plugs that check good on the pressure/bomb test box still don’t work properly in the engine. Resistance checks supplement normal cleaning and pressure checking.
Why Use 5000 Ohms as the Cut-Off Point?
Five thousand ohms of resistance is a good cut-off point because it provides a value between where spark plugs are manufactured and where problems seem to appear with high resistance. Most reports Tempest receives about rough running engines associated with high spark plug resistance involve values of 7000 ohms or more. Nothing is magical about 5000 ohms, but using it as a cut-off point for spark plugs has proven to work well; just like using 80/60 for compression checks works well.
New Spark Plug Resistance
Resistance values differ between manufacturers. Champion Spark Plug Company’s Engineering Manual gives the nominal value for their resistor type of aviation spark plugs as 1000 - 1500 ohms (no +/- value is shown, but minus 400 and plus 1000 probably wouldn’t be unreasonable). Tempest’s “fired in resistor” nominal value is 2500, +/- about 1000 ohms. The absolute values for new plugs aren’t too important as long as they are fairly low; say less than 4000 ohms and remain reasonably stable throughout the plug’s life. Ask your spark plug sales man for the “as manufactured” resistance of his new spark plugs. Then you can compare that to new plugs as received and older plugs during cleaning and inspection.
Resistor Stability – Check Plugs Before You Install Them
Resistance instability is at the heart of high resistance spark plug problems. If resistance increases significantly after the plug is manufactured, what was once a good plug becomes a bad plug. Check resistance of all new and reconditioned/cleaned plugs prior to installation. Old technology “stack type” resistor design plugs sometimes come right out of the box with resistance values several times that at which they were manufactured. This type of resistor design is also recognized as sometimes drifting high in service. You’ll save time and money by not putting high resistance plugs in an engine just to have to take them out when you find that they’re causing the engine to run roughly. Resistor-drift is not a problem with the Tempest’s “fired in” resistor design.
What About the Low Limits for Resistance?
The resistor’s biggest job is to help provide a sharp, clean ‘pulse’ type spark. If the spark ‘dribbles’ across the gap in the beginning, it doesn’t light the fuel/air charge properly. If it dribbles at the end of the spark, it eats away at the spark plug electrodes and other ‘arc gap’ components in the magnetos, shortening their useful life. The lowest spark plug resistance that seems to perform the task of chopping off the front and back “tails” of the spark is about 500 - 600 ohms. Fortunately, excessively low resistance is almost never a problem.
Serviceable Spark Plug Resistance
To help assure reliable and trouble free operations, Tempest recommends replacing spark plugs in service having a resistance value of more than 5000 ohms (5k ohms) or less than 500 (0.5k ohms). For new plugs, we recommend 4000 ohms as the maximum acceptable value.
Additional Information
For additional information on this Tempest Tech Tip and Tempest products, please call (800) 822-3200.
It is funny to watch an owner's eyes when you ohm a plug and it is high and I take it gently over to the bench, place a rag over it and smash it with a 3lb hammer, that way it never goes back into the airplane...because if they cant afford a replacement plug, they shouldn't be flying..
spark plug criteria
Stolen from QAA
Background
Discussion about the “right” way to check spark plug resistance can go on until the cows come home. While what happens when 10,000 volts is forced across a resistor under laboratory conditions is interesting, it is hardly relevant to resolving the problems faced by IAs, A&Ps and AEs. The question is; “What’s causing the rough running engine and how can we fix it?” Conditions on a blazing hot or freezing cold ramp aren’t laboratory conditions. What we, as aircraft technicians, need is a useful available tool to identify a spark plug that might be causing a rough running engine.
Military Specification MIL-S-7886 provides guidance for aviation spark plug manufacturers. It addresses checking spark plug resistance using a low voltage ohmmeter. Hundreds of millions of spark plugs later it’s safe to say that the MIL Spec’s advice is good. A typical low voltage ohm meter (or the Tempest AT-5k meter which relies on a low voltage circuit) can help identify suspect plugs. Although many volt meters use nine volts batteries, that’s close enough. The “low voltage” referred to doesn’t hinge on exactly 8 or 10 volts. It addresses the difference between a “megger” or high voltage resistance check, say 500 to 1000 or more volts, and a typical shop floor meter’s use.
Resistance checks DO NOT replace the familiar spark plug cleaner/pressure bomb test box that actually sparks the plugs under air pressure. However, the pressure bomb doesn’t check resistance, and as we know from experience, sometimes plugs that check good on the pressure/bomb test box still don’t work properly in the engine. Resistance checks supplement normal cleaning and pressure checking.
Why Use 5000 Ohms as the Cut-Off Point?
Five thousand ohms of resistance is a good cut-off point because it provides a value between where spark plugs are manufactured and where problems seem to appear with high resistance. Most reports Tempest receives about rough running engines associated with high spark plug resistance involve values of 7000 ohms or more. Nothing is magical about 5000 ohms, but using it as a cut-off point for spark plugs has proven to work well; just like using 80/60 for compression checks works well.
New Spark Plug Resistance
Resistance values differ between manufacturers. Champion Spark Plug Company’s Engineering Manual gives the nominal value for their resistor type of aviation spark plugs as 1000 - 1500 ohms (no +/- value is shown, but minus 400 and plus 1000 probably wouldn’t be unreasonable). Tempest’s “fired in resistor” nominal value is 2500, +/- about 1000 ohms. The absolute values for new plugs aren’t too important as long as they are fairly low; say less than 4000 ohms and remain reasonably stable throughout the plug’s life. Ask your spark plug sales man for the “as manufactured” resistance of his new spark plugs. Then you can compare that to new plugs as received and older plugs during cleaning and inspection.
Resistor Stability – Check Plugs Before You Install Them
Resistance instability is at the heart of high resistance spark plug problems. If resistance increases significantly after the plug is manufactured, what was once a good plug becomes a bad plug. Check resistance of all new and reconditioned/cleaned plugs prior to installation. Old technology “stack type” resistor design plugs sometimes come right out of the box with resistance values several times that at which they were manufactured. This type of resistor design is also recognized as sometimes drifting high in service. You’ll save time and money by not putting high resistance plugs in an engine just to have to take them out when you find that they’re causing the engine to run roughly. Resistor-drift is not a problem with the Tempest’s “fired in” resistor design.
What About the Low Limits for Resistance?
The resistor’s biggest job is to help provide a sharp, clean ‘pulse’ type spark. If the spark ‘dribbles’ across the gap in the beginning, it doesn’t light the fuel/air charge properly. If it dribbles at the end of the spark, it eats away at the spark plug electrodes and other ‘arc gap’ components in the magnetos, shortening their useful life. The lowest spark plug resistance that seems to perform the task of chopping off the front and back “tails” of the spark is about 500 - 600 ohms. Fortunately, excessively low resistance is almost never a problem.
Serviceable Spark Plug Resistance
To help assure reliable and trouble free operations, Tempest recommends replacing spark plugs in service having a resistance value of more than 5000 ohms (5k ohms) or less than 500 (0.5k ohms). For new plugs, we recommend 4000 ohms as the maximum acceptable value.
Additional Information
For additional information on this Tempest Tech Tip and Tempest products, please call (800) 822-3200.
Last edited:
skywagon8a
MEMBER
SE Mass MA6
With an all cylinder EGT instrument installed in the airplane, a faulty plug can be found in less time than it takes to read your post without removing the cowl.
texmex
MEMBER
Hanging Rock, Australia.
To be fair, Cub Builder is correct. Lot's of old discussion on this at the Beechtalk site. I'll have to re-visit it as I thought it was more then a simple ohm bench test needed. But looks like I have that wrong.
$1,000 Eddie. $1600 for me in my Ozzie dollars by the time I converted and every bludger along the way took their slice.
I bought them hoping to smooth out my engine, but they won't cure seized counterweight bushes, unfortunately. :sad:
That just adds weight, the ounces add up to pounds quickly. If you run good plugs and get a legitimate annual and change them when they are borderline, it doesn't add any weight or require an electrical system. Light airplanes are good airplanes.
skywagon8a
MEMBER
SE Mass MA6
EGT instruments do not require an electrical system. Some do, but some don't. They have proven their worth for more than half a century which was far more important than the few extra ounces. Their use also saves a large amount of mechanic $$$ which could be used for 100LL.
wireweinie
FOUNDER
Palmer, AK
I'm going to sound grouchy here.
You're assuming that the operator will monitor and UNDERSTAND the data displayed on the gauge. Temps or changes in temps on EGT and CHT gauges have different causes and sometimes need to be cross referenced with data from other systems. Some ignore the readings, some sit and stare at the gauges, but, hopefully, some will ask a mechanic or engine shop about possible problems. Maybe before any further problems?
Web
skywagon8a
MEMBER
SE Mass MA6
Web,
All I'm suggesting is that when a pilot runs up his engine doing a mag check and he gets some rough running or high drop, a quick glance at the EGT instrument with a quick flick of the selector switch will show which plug is running considerably colder than the others. That will be the bad plug.
All I'm suggesting is that when a pilot runs up his engine doing a mag check and he gets some rough running or high drop, a quick glance at the EGT instrument with a quick flick of the selector switch will show which plug is running considerably colder than the others. That will be the bad plug.
