I forgot? Oh! Is a coil a coil?

[Callahan]

I was going to post something & forgot what I wanted to post. A 68 year old brain will do that! Let me think.....duhhh.....

 

Oh yeah!

 

Has anyone had this experience? My Drifter with a 503 inverted was very hard to start. Figured the inverted plugs were flooded all the time. For the heck of it, I pulled a fairly new coil off a spare motor I had. Stuck it (only one) on the Drifter....sucker cranked on one or two spins & does so now every time! It wasn't a fluke!

 

Now, people have told me that a coil is a coil.....they either work or they don't. I say B.S.! Both coils tested to spec but one was newer! The motor continues to crank easily, often on the first revolution.

 

Anybody want to respond? Would love to have some input.

 

 

[Deskpilot]

Possibly not the coil but rather its connections, particularly the ground (earth) wire.

 

 

[facthunter]

Coils age. Testing them is not that straightforward as they break down usually when hot. Aging material breakdown oxidation etc (any moisture is deadly) reduces the resistance of the material separating the very fine windings in the HT side, and the coli leaks and gets hot. Vibration of the motor is another cause of failure. Continuity test is of limited value, but is a test you can do easily so still worth doing as if it fails that test don't bother further. Some test by running the coil for hours at a high gap, on a bench set up. It can sometimes take that long to show a fault. They don't last forever and should be stored in a sealed plastic bag. If a plug lead falls off and it's open circuited that can kill it, as it will track internally. Electricity finds the path of least resistance. Nev

 

 

[Callahan]

Possibly not the coil but rather its connections, particularly the ground (earth) wire.

Thanks Doug but I didn't touch or improve anything else. I just removed the original coil, put the newer one on, that was it. I may have sprayed those twisty screw head coil connections with electronic spray but that was it. It'd be hard for me to believe that a simple spraying would cure a hard start. Possible I guess?

 

 

[Callahan]

Coils age. Testing them is not that straightforward as they break down usually when hot. Aging material breakdown oxidation etc (any moisture is deadly) reduces the resistance of the material separating the very fine windings in the HT side, and the coli leaks and gets hot. Vibration of the motor is another cause of failure. Continuity test is of limited value, but is a test you can do easily so still worth doing as if it fails that test don't bother further. Some test by running the coil for hours at a high gap, on a bench set up. It can sometimes take that long to show a fault. They don't last forever and should be stored in a sealed plastic bag. If a plug lead falls off and it's open circuited that can kill it, as it will track internally. Electricity finds the path of least resistance. Nev

Nev! Thanks for that informative disclosure! I'll show it to my friends who say a coil either works or it doesn't. From what you've told me, a coil can still work but deteriorate under running pressure & heat. Thank you!

 

 

[Callahan]

Oh Crap! From what you've told me about a plug wire coming loose.....and killing the coil......I landed my Drifter two days ago, notice a plug wire hanging off....I'll have to check now & see if I have a bad coil. I haven't flown it since then.

 

Thanks again.....I had forgotten to safety wire the inverted plug caps!

 

 

[onetrack]

Failure with increased temperature is a classic electrical and electronic component signature.

 

Often had numerous coil failures over the years, where coils worked when cold, and failed when hot.

 

Got a mate with a tilt-tray truck, he often gets called out to pick up vehicles that have stopped with ECU or other electrical, or electronic component failure.

 

He says to me, "You NEVER, EVER, try to start the vehicle, once you arrive to pick it up! The reason being, it has cooled down, and 9 times out of 10, it will start right up again! Then the owner jumps in, says 'Great!' - and drives off! - meaning you've lost your towing job!!"

 

"What you do, is - you winch the vehicle on without even attempting to start it - then when you get to the specified destination, you then start it up, and drive it off!"

 

 

[Callahan]

Failure with increased temperature is a classic electrical and electronic component signature.Often had numerous coil failures over the years, where coils worked when cold, and failed when hot.

Got a mate with a tilt-tray truck, he often gets called out to pick up vehicles that have stopped with ECU or other electrical, or electronic component failure.

 

He says to me, "You NEVER, EVER, try to start the vehicle, once you arrive to pick it up! The reason being, it has cooled down, and 9 times out of 10, it will start right up again! Then the owner jumps in, says 'Great!' - and drives off! - meaning you've lost your towing job!!"

 

"What you do, is - you winch the vehicle on without even attempting to start it - then when you get to the specified destination, you then start it up, and drive it off!"

....and I bet that bit of advice came with experience! Funny too! Thanks!

 

 

[bexrbetter]

Yup, sure can have crook coils.

 

Make sure you have the appropriate voltage coil as well. 9 and 12 are the most common and many a person has put a 9 volt coil on 12 volt sans ballast resistor. They don't last long.

 

A ballast resistor allows full 12 volts when cold so the 9 volt coil has extra 'oomph' for starting, but will burn out quickly if left like that. The ballast resistor heats up quickly after starting and drops the voltage to the appropriate 9 volts.

 

I worry your sudden great starting is because you have put a 9 volt coil on but you haven't also added a ballast resistor?

 

 

[onetrack]

Don't recall ever seeing a 9V coil with resistor, all the resistor-type coils I have ever seen were 7.2V.

 

But yes, Bex is on the mark, look to see if the coil is marked with the actual coil voltage, or marked, "use with resistor".

 

The later model "hi-intensity" or "high-voltage" coils have a heavier primary winding to produce a higher voltage spark - up to 40,000V.

 

High voltage is good when it comes to reducing plug misfires.

 

 

[facthunter]

I wouldn't consider the resistor suitable for aircraft use. It runs quite hot,and is something else to go wrong . I've only seen it on Ford Cortina's produced in the 60's.

 

It's designed to compensate for the voltage drop on a battery when it's cranking the starter, where the resistor is bypassed by a tapping on the starter solenoid, allowing what's left of the nominal 12 volts to make good sparks for starting. Think it's only used on "Points" type ignition, not CDI. Nev

 

 

[bexrbetter]

I wouldn't consider the resistor suitable for aircraft use.

No one here was advocating their use.

 

Don't recall ever seeing a 9V coil with resistor, all the resistor-type coils I have ever seen were 7.2V.

I can't vouch for every car every made, but the majority are 9 volt (resistor'ed systems).

 

You might be thinking of 6 volt systems that are actually 7.2 volt.

 

 

[M61A1]

Unless this is an old engine with points, the "coil" also has the CDI (Capacitor Discharge Ingition) built into it. Your coil could have perfect resistance and the CDI can still be dead.

 

 

[Downunder]

Had a heck of a time finding a faulty coil on a car..... I was young and before the internet. Started fine cold.... but not hot......

 

I believe iridium plugs help with starting on the inverted 2 strokes....

 

 

[onetrack]

You might be thinking of 6 volt systems that are actually 7.2 volt.

No, I distinctly recall that all the old (60's-70's) ballasted 12V Holdens that I owned or worked on, had coils marked 7.2V.

Maybe they were all fitted with surplus FJ Holden stock coils?

 

 

[Callahan]

Down under,

 

I did think about using iridium plugs but the cost factor. Now that it starts easily, I'll keep the status quo. Thanks!

 

Had a heck of a time finding a faulty coil on a car..... I was young and before the internet. Started fine cold.... but not hot......I believe iridium plugs help with starting on the inverted 2 strokes....

[Downunder]

NGK 6747 BR8EIX, is what you want if you ever devide to try.....

 

Should be able to pick them up for US$8.00 ea or so...... A friend is getting a reliable 50hrs on a 582..

 

 

[onetrack]

You can get genuine Denso, Toyota and NGK Iridium plugs out of China for very reasonable cost, via AliExpress.

 

You just have to be patient, they are freight-free, but they send them via slow boat. They generally take about 3-4 weeks to arrive.

 

 

[facthunter]

Don't use plugs with "R" in the part description. This will make coil failure more likely, same as non wire (carbon) leads Those things are used in cars for interference suppression (TV etc). High resistance in the secondary invites tracking somewhere else.

 

I would rather use the normal plugs and change when more often. They are about 1/3rd the price. The insulator is the same material and that's what fails due crap on it. If you do your own servicing it's a no brainer. Watch the air gap. On a lot of plugs today it's set far too wide for aircraft engines. .022" say .5 mm is OK. You will get better starting and less load on the coils etc . Nev

 

 

[Callahan]

Nev.....you da' man! I'm not leaving you other responders out either because you all know more than me!

 

Over the Weekend News:

 

Drifter: 503 B-box

 

1) Cured hard starting Drifter with newer coil. Hooray.

 

2) Showed my friend Nev's response on coil breakdown.His reply? ...Oh! Sounds like he knows what he's talking about!

 

2) High speed vibration under 5k rpm still hanging in like a cold you can't get rid of. I use Marine 93 octane.

 

Trike: 503 - B-box

 

1) Mid-range vibration at 5k & below still hanging like a cold.....this is heavy vibration not hi-speed like the Drifter.

 

Tried 3 different props, six separate carbs, syncing carbs multiple times, cleaned up electrical, switch checked, all contacts cleaned, new 14 gauge wiring, pulled Facet pump & squeeze bulb out of line, tried a small jar with gas held high to eliminate all "in-line" fuel delivery problems, new leads, new plugs at .18 gap, added one coil from another motor, bought two Balance Masters....no help what-so-ever, prop tracking okay, new carb needles, tried different carb needle positions, thoroughly cleaned all carb inlets, outlets, jets, & a myriad of other remedies I've lost track of.

 

Mid-range is killing me.

 

 

[onetrack]

Heavy vibration sounds to me like a substantial rotating component is out of balance.

 

A dial indicator placed on every major rotating component, and then rotating it, will pick up bends in components and components that are not mounted true. Flywheels in particular, need to be checked with a dial indicator to ensure they're within runout specs.

 

 

[Callahan]

One Track,

 

My sentiments exactly.

 

I have done everything humanly possible & redone them so many times, I've forgotten what I've done. However, my mechanical skills are lacking so I'm still beating my brains out trying to figure something simple I haven't thought of.

 

I appreciate your advice. Today will be my last day at the grindstone...or a bullet in the brain.

 

Bill Catalina

 

 

[facthunter]

It's possible you are getting detonation. with the leaner mid range fuel flow setting. Some oils drop the octane rating of the fuel mix, whether it has a pump or not. Try a GOOD oil and higher octane fuel. Don't use outboard (TCW3). Its a different formulation. Pennzoil a few years ago made a special formulation for aircraft use two strokes. It's probably only available in the US. Check also if you have carbon deposits or the plugs are too hot. or you could have crankshaft runout or a bearing with play, or a crack developing near the drive gear crank web. Nev

 

 

[Methusala]

A friend a few years ago discussed fine wire electrode spark plugs. Said that having a far smaller radius to the tip meant that lead could not foul plugs as easily because the spark always originated at the tip, not moving around as on a broader surface with thick electrode. That and the superior voltage available from cdi ignition meant that they never had plug fouling with their competition 2 strokes that ran on avgas.

 

For what its worth, Don

 

 

[Callahan]

Nev,

 

I use 93 octane E-free, Marine and that expensive 2-stroke oil that WallyMart sells at $36.00 per gallon.

 

As far as detonation, I had a 503 bore a hole in a piston a while back. If you watched my video, that watery recovery effort was because of it.

 

I'm editing a video now of the vibration. I'll put the YouTube link on here when finished.

 

Thanks a lot!

 

Bill Catalina

 

It's possible you are getting detonation. with the leaner mid range fuel flow setting. Some oils drop the octane rating of the fuel mix, whether it has a pump or not. Try a GOOD oil and higher octane fuel. Don't use outboard (TCW3). Its a different formulation. Pennzoil a few years ago made a special formulation for aircraft use two strokes. It's probably only available in the US. Check also if you have carbon deposits or the plugs are too hot. or you could have crankshaft runout or a bearing with play, or a crack developing near the drive gear crank web. Nev