how to test ignition coil

Ben Elsewhere /

Does anyone have a clue how to test an ignition coil to see if it is functional? i.e. with a mutlimeter.... Do they normally fail?

I'm still trying to troubleshoot the ignition system on my Indian. The plug is good, the magneto is putting out juice, because I can beep the horn I hardwired to the battery.

It must be one of these, correct?

Wiring Problem

Condensor

*Ignition Coil

Which should I suspect first, which is the most common failure?

The 'ped failed all of a sudden during a 10 mile-ish ride, if that's a helpful clue.

Thanks a lot in advance!

--Ben

Re: how to test ignition coil

lots of things can stop an engine and not let it start again. Why or how have you narrowed it down to an ignition problem?

I guess you can check for continuity in the two coils within the coil. .. but a coil can fail in other ways besides a dead short. Without the manufacturer's coil-ohms-testing guidance i dont think you can determine if just a part of a winding is toast.

Re: how to test ignition coil

Don Pflueger /

the first thing i would do is try a new plug. coils rarely ever go bad. if there is continuity, its a fair bet that its good. the wire or the boot on the plug wire may be bad. usually ignition problems are caused by;

1- bad spark plug

2- dirty or misadjusted points

3- weak condensor

4- bad wiring

5- bad kill switch

6- blown tail light or brake light bulb.

rusty magnets and pick ups on the charging coils can impede spark too. you need to look everything over closely to determine whats wrong. 9 times out of 10 its something simple. if your boke has a battery, check the fuse.

Re: how to test ignition coil

Ben Elsewhere /

thanks for the quick responses!

I know it's an ignition problem because it has fuel, compression and _no spark_.

The spark plug seems fine... I stuck it in my snowblower and gave a haul on the starter and got some fat blue sparks.

donp - I'll work my way through that list. Thanks a lot.

--Ben

Re: how to test ignition coil

Don Pflueger /

a plug can have spark, but still be bad. the reason;

spark plugs work in a similar matter to a glow plug. the ceramic core heats up to a certain temperature. the spark ignites the fuel/air mix and the red hot ceramic core completes the burn. that is why plugs have different heat ranges. they are calibrated to work with specific engine displacements.

but you say you have no spark at all, so its going to be something in that list i posted.

Re: how to test ignition coil

Try a new plug as has been sugested, it can make all the difference in the world.

I spent several days one time trying to get my moped running when I first got it. Tested the spark, and it seemed good, big blue spark, as did the spark plug. I finally ran out of things to try and got a new plug and it started right up. If I had just put in a new plug to begin with I could have had the bike running in minutes, not days.

Besides, a new plug is only about $1.00 so you can not go too wrong by replacing it.

Re: how to test ignition coil

you say you hardwired your horn to the battery....if so that would have absolutely nothing to do with the ignition.

Re: how to test ignition coil

Ben Elsewhere /

Ryan - The battery is charged off of the magneto, so the fact that the horn works is evidence that there is electricity coming off of that, thats all I was saying.

I think I may have found the problem... A crapped out spark plug boot.

I got a solid shock when the boot + connector were removed from the end of the cable coming from the coil, but nothing when the boot, plug, etc... were put back. Not the most scientific testing method, but it does make it obvious where the juice is.

Thanks a lot for the help!

--Ben

Re: how to test ignition coil

Don Pflueger /

if its a resistor boot, and a resistor plug, that will cause a no spark situation.

Re: how to test ignition coil

Ben Elsewhere /

it is a resistor boot. so i just need to slap a new one on, right?

Merry Christmas!

--Ben

Re: how to test ignition coil

Don Pflueger /

yep. youy can get them at any motorcycle or lawn mower repair shop.

Re: how to test ignition coil

Hi Don -

I have had the issues with getting spark on my 1985 Garelli Basic after changing spark plug caps. I have tried two new caps and get nothing.

I have been reading other threads trying to figure this out and came across your advice here.

How can I tell if I have a resistor boot and a resistor plug?

Thanks!

Re: how to test ignition coil

Resistor plugs usually have an "R" in the type number. Or you can measure the resistance from the terminal on the end to the center electrode, it will be close to zero in a non-resistor plug. Same thing for the cap, measure resistance from where the wire goes to where the plug goes. There is also resistor wire. It has a carbon-fiber center instead of copper. It's almost universally used on cars, if you took your wire off of a car.

To be on the safe side use non-resistor parts throughout. The resistor is just to reduce interference to people's radio and TV reception. Though having one resistor part (not more) should not affect your engine performance.

Re: how to test ignition coil

im having a very similiar issue. cimatti city bike. no spark at all. figured it could be my tail/brake bulb. it looked ok, but i took it out and put wire over the leads to make sure there was connection. still no spark. so i took off the plug boot to see if that was faulty. i shaved the end of the wire down to the copper and grabbed hold of it, and spun the flywheel. it shocked me. so i ran out, got a new plug boot, and it didnt do anything. i even wrapped the copper wire directly around the metal tip of the spark plug, and nothing. the MOST i could get was maybe a spark every now and then when i held the bare copper to the cylinder. maybe the plug wire is bad. i dunno

Re: how to test ignition coil

Steve - if you find a solution let me know!

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