How to know if coil is bad?

[sdnomad]

I have a Stihl 009L that is not running well. I do have spark but the spark doesn't look real strong. I do have a new spark plug installed. If the coil is bad, would I have any spark?

 

[WoodChuck'r]

Yeah you can have spark with a bad coil.

A common indication is they run decent until they warm up. Once they get warm they die out as if they're out of fuel.

 

[rob066]

How is the air gap between the coil and flywheel. I use a business card to set the gap like many others do.

 

[sdnomad]

This saw is hard starting and it runs rough. I think I will start with a carb rebuild and see if that takes care of the problem.

 

[ncfarmboy]

Had the same problem on 009 I worked on. Had spark wouldn't run. New plug. Rebiult carb. Tried another carb. Rebuilt it. Another reed valve no luck. Put a new coil on it prob. solved.
If I remember correctly air gap is .008 it will run @ .012 which is what I set it. Did not know @ the time it set closer. Might be the hard start problem. Mine is hard start. May go back and set closer to see if that corrects it.
Shep

 

[blackoak]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

 

[CJ1]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

Who do you get to remove the screwdriver out of your rearend after the test???? CJ

 

[angelo c]

Who do you get to remove the screwdriver out of your rearend after the test???? CJ

Rear end ? My you have a loving wife...mine would be straight in the neck. then she would have my other tools lined up near by to make it look like i was working on a saw and fell over...probably spill some beer and make it look like i was drunk ect. yup she watches way too much Investigative Discovery channel.

 

[bplust]

Make sure that the plug wire is twisted in the coil good and firm, and that there are no weak spots or breaks along the wire, and it's connected to the spark plug connector well.

 

[archerjda]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

My dad used to pay me 10 cents to hold the screwdriver.

 

[Vintage Engine Repairs]

2 affordable ways to test a coil

1).Get an adjustable spark tester. It should
Clear 6mm and be bright blue or white. If it’s yellow or orange and doesn’t clear that gap, it could be the coil.

2).check the resistance of the primary and secondary windings in the coil. I’d guess they are out of spec. I have a video on testing the coil with a multimeter if you’d like me to send it?

 

[WoodChuck'r]

What the hell

 

[Clyde85]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

Brave man.

 

[lone wolf]

Rear end ? My you have a loving wife...mine would be straight in the neck. then she would have my other tools lined up near by to make it look like i was working on a saw and fell over...probably spill some beer and make it look like i was drunk ect. yup she watches way too much Investigative Discovery channel.

Must be a Sicilian!

 

[Wood Doctor]

I recently ran into a Husky 50 that had what looked like a good spark. It would start sometimes and sometimes not. Even if it started, it would die out after running awhile. I replaced the coil and that solved the problem. Nothing lasts forever, and this saw might be about the same age as your Stihl 009L (circa 1989).

 

[tomalophicon]

I have a Shindaiwa that looked like it good spark but would only start after 30 pulls and sometimes not at all. Coil gapped correctly.
Replaced the coil after rebuilding two carbs (among other things) and it's perfect now.

 

[angelo c]

Must be a Sicilian!

naw...she's "Murican" and feisty !!!

 

[Wood Doctor]

I must admit that if I find what I think is a good spark, I temporarily figure that I have a fuel or compression issue. If the compression tests good, then I look to the fuel system next. In thread #15 above, I changed out the carb but surprisingly there was no improvement. At last resort, I replaced the coil because there was very little remaining that could have caused this problem. Bingo. The coil was the culprit.

 

[Bobbyg123]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

Good one

 

[John Oh]

One way I test my coils is to place a screw driver in the plug boot and have my wife to hold it while I crank the saw over. You will know quick if it's bad or not. This test usually only works one time if the coil is good, but you may get to do a few test at least before you get a good one.:msp_smile:

IF THE WIFE JUMPS YOU KNOW ITS GOOD!