How to check a two piece ignition with a multimeter.

[idiotwithasaw]

Here is what I have, where do I begin, and what numbers an I looking for. How is this different from a one piece ignition coil?

 

[idiotwithasaw]

 

[wcorey]

You can check the winding's for continuity and resistance (which really would require a specification, such as 3 or 6 ohms) but that rarely seems to be the issue. Usually it's the trigger circuitry and you'd probably need a schematic and access to the individual components to figure that out.
In general I've found that the module is most likely the culprit, not the coil.

 

[Cut4fun]

I just had one that was the coil bad in a 2 piece.

 

[VK Johnson]

I'm gonna weigh in with something that will probably go over like a fart in church my side business...once my main business...is major appliance repair. If I spent my time testing things with a multimeter like they suggest doing in the official shop manuals, I would have either not made a dime, or charged the customers so much that they would never use me twice! And I would have been wrong the majority of the time!

Why is that, you say? How can this be? Well, testing is fine, but seat of the pants and intuition have worked MUCH MUCH better over the years! Yes, it means that I use the 'shotgun method', but my success rate is dern near 100%.

The thing about using a multi meter is that even though it tests wrong, the part can be bad...way bad. Or, if it tests wrong, the part can be just fine. If your diagnosing is leading to a particular part, I wouldn't depend on the multimeter to confirm that...better to just depend on your own intuition, assuming, of course, that you know what you're doing. The thing that a multimeter does extremely well is a simple continuity test. Good...or not good. That's the only reason I carry one.

In short, a multimeter will lead you down the wrong path more often than not! Now, y'all engineers and wanna be engineers...FLAME ON!!! LOL

 

[idiotwithasaw]

Ok I'm about to sound stupider than I already do. But which is the coil Amd which is the module?

 

[wcorey]

Coil is the one with the spark plug lead, module has the laminated iron core and sits closer to the flywheel.

 

[idiotwithasaw]

Ok so on the coil am I checking for resistance or continuity? And the same for the module? The module has two wires, positive and ground. When I checked it with the leads on the two wires it tested somewhere around 25 m ohm, which sounds awful high.

On the coil when I checked the primary and secondary it seems like it was within spec, I don't remember the numbers as I did them this morning, I'll retest it tomorrow and post it if I can remember.

 

[wcorey]

On a coil you first check for continuity, that just shows whether there's still a continuous, unbroken circuit. If that's OK then you can check the resistance but that really only applies to a coil with just a plain winding. As soon as theres triggering circuitry involved like with the module or one peice ingnition coil, then the resistance may not mean much unless possibly you have some specific specified value to shoot for.

 

[idiotwithasaw]

When checking continuity on a coil where should I check it, which wires do I use?

Sent from my HTC One using Tapatalk

 

[Al Smith]

Ignitions in a nut shell http://www.foxvalleykart.com/timing1.html

 

[wcorey]

You'd check primary resistance between the wire coming from the module and ground, should be a very low ohm reading, possibly less than 1. Usually need a very good quality meter for this.
Secondary winding is checked from the plug wire to ground, much longer winding so should be a much higher reading, like maybe 5-10k.

 

[Al Smith]

For simplicity an ignition coil is basically an auto transformer .The solid state trigger device which takes the part of the points senses a fall in the sine wave of the pulsated DC generated from the magnets passing the coil .

Some coils will self advance, some will not .

 

[idiotwithasaw]

This is all good information. So you are both saying that the coil can be tested but the module can't?

 

[Al Smith]

The way I see it the trigger either works or it doesn't because there's no fixing it if it doesn't .

As a rule on any ignition system be it points coil,battery,magneto or solid state like a saw the problem usually is on the low voltage side .The trigger in this case is the low voltage side.The dang things are sealed units and here's no repairing them

Now I did have a weed wacker that had low magnetism on one of the flywheel magnets but that's odd and another subject all together.

 

[Al Smith]

You can get some odd stuff on small engine ignitions .I have a Stihl 042 which uses an auto advance coil .Danged thing drove me nuts .Would not advance .Started easy but died on the vine about half throttle .Swapped out the coil from an 048 and it did fine .
12 HP Briggs mower engine .self advance .Son of a bee would get hot and stick on full advance until it cooled off .Hot you couldn't crank the engine ,fired way too soon.

 

[idiotwithasaw]

Ok I bought a powerhead off feebay hoping it had a good ignition system. Which surprise it did got my little echo weed wacker up and running slicker than chit. While I had it on the bench I checked both coils and they both had a primary circuit reading of 2ohm and the secondary had a reading of 2.1 kohm on both, and the primary also checked good on continuity on both coils. So I just ended up using my original coil and swapping the module.

On the module I couldn't get a useful reading off of either of them. I just swapped them and it had spark after that.

So in conclusion in a two piece ignition apparently the coil can be tested but the module cannot. That's my findings anyway, I am probably wrong.

 

[idiotwithasaw]

Ok I bought a powerhead off feebay hoping it had a good ignition system. Which surprise it did got my little echo weed wacker up and running slicker than chit. While I had it on the bench I checked both coils and they both had a primary circuit reading of 2ohm and the secondary had a reading of 2.1 kohm on both, and the primary also checked good on continuity on both coils. So I just ended up using my original coil and swapping the module.

On the module I couldn't get a useful reading off of either of them. I just swapped them and it had spark after that.

So in conclusion in a two piece ignition apparently the coil can be tested but the module cannot. That's my findings anyway, I am probably wrong.

 

[Mark71gtx]

I have dealt with some of those triggers before. I have found that if you find a coil that does not require an external trigger module (from a tool that is newer with the same dimension coil) more often than not, it will work.

 

[David Young]

you can test the module in one manner.
one multimeter lead goes to ground. case ground somewhere and the other lead goes to the input to the coil this is the low side.
you will likely be able to test DCv or AC v

pull the engine over you will have voltage or not. you can also use a cordless drill to make life easier.

does that help at all?