395XP Ignition Coil Questions . . .

[TexasTimbers]

Let me get my questions out of the way first then give some background:

1) Can an ignition coil be 'bad' yet still produce a blue spark at the SP electrode?

2) Are the cheaper aftermarket coils worth the $50 lower price tag? I have no problem spending the extra coin on OEM if the aftermarkets are known to be of lesser quality.

Now a little history f why I want to replace the coil. I've eliminated everything except the coil IMO. The saw had sat (again) for a couple years so I put a new kit in the tillotson. It still wouldn't start so just to make sure it wasn't a fuel issue I broke out the ether (don't like to but hey it helps with troubleshooting) and it still won't hit a lick. Won't even burp.

So then I inspected the coil and magnets and all are nice and shiny - no rust or corrosion. Coil gap is set correctly. So I wired the plug to the jug and pulled and got a strong bright blue spark every time I pulled. So I'm thinking I have fuel for sure (ether should have busted off no matter what if everything else was good) and a good spark. Leaves me scratching my head. SO I put the compression tester on it and it has 125 PSI which is damned good. So next I pulled the kill switch wire off and tried it again but had that been the issue I wouldn't have gotten a blue spark at the plug in the first place, but now I can say I did it.

This saw has given me fits before. Something different every time. The only thing I know to do at this point is replace the ignition coil regardless of the blue spark. Any other thoughts on troubleshooting this are welcomed.

I know it's getting air & fuel, so regardless of the blue spark I'm thinking the coil has to be it. What do you think?

 

[Chris_In_VT]

125psi compression? Is that a typo? 125 is not very good. My 395 with a gasket delete is over 200psi. I'd expect a healthy stock one to be 170+

 

[TexasTimbers]

I thought the compression was supposed to be in the 90 - 120 range. If it's supposed to be 170+ then that's obviously a problem.

 

[TexasTimbers]

I wonder if the decomp valve is bad. I made sure it was out for the test but maybe it's leaking?

 

[TexasTimbers]

I had stopped pulling the cord after 3 pulls the first test. I kept going this time and got it up to 150 - seems a little low yet if it's supposed to be no lower than 170.

 

[Chris_In_VT]

I was going to ask if your gauge has a schrader valve- that can give low readings. Yes, pull until the gauge stops climbing. 150 is not bad.

 

[TexasTimbers]

My old tester was untrustworthy so I bought a brand new one at Oreilly's today I feel pretty confident in the tester. I guess I am back to the coil then. Now just need to know what other's have experienced with the cheaper aftermarket coils. Think I'll just go ahead and order a Husky so I don't have to wonder.

 

[mdavlee]

160-170 is common for one. I have the same tester at home and it reads the same as my snap on gauge. Coil could be the problem but seems unlikely just from sitting. Where are the carb screws set?

 

[TexasTimbers]

Where are the carb screws set?

I don't know. They are in the same place as when it was put up a couple years ago, and no matter where they are at, it should have at least busted off a few hits with that ether in the cylinder don't you think? .

 

[TexasTimbers]

I thought maybe a mud dobber had bult a nest in the muffler - I have had that happen to my dolmar weedeater several times and it kept it from cranking - but when I blow air into the jug it comes out of the muffler freely so I doubt that's it. I might pull the muffler anyway. At some point I'm going to have to tear it completely down and do a visual. I just went to Oreilly's and bought a spark tester and it says the coil and plug are both fine.

 

[mdavlee]

It could be the ground for the coil. Unhook the switch and see if it will hit then. That's the only other part of it besides the coil.

 

[marti384]

Is it flooding? Dripping wet plug won't fire ether.

 

[decableguy2000]

You could have great spark and good fuel, but have bad timing it will not run right make sure you haven't sheared the flywheel key. My 394 had a dead coil no spark what so ever. Tried an aftermarket coil and it ran okay but not great so I ordered an OEM and the same result. Ended up being a carb issue. Send me a PM if want to try an after market.

Jeremy

 

[TexasTimbers]

It busted off and ran for about 10 seconds. It isn't a fuel issue because when it started I had the ingnition tester inline. Once it quit I pulled the rope 15 times and the ignition didn't spark even once. Bad (intermittent) coil? I've checked and double checked the gap and coil ground.

make sure you haven't sheared the flywheel key.

How do I check that witout tearing it down? Should the piston be TDC when the magnets are lined up with the coil etc.? But it wouldn't have ran those 10 seconds even if it was sheared correct?

 

[decableguy2000]

Just pull the fly wheel off and check. I believe 395 key is cast into the flywheel. With it running for a few seconds I would suspect a fuel issue or an air leak. Have you pressure and vacuum tested the saw yet? Are you using a spark tester with a little bulb in it, I found them to be unreliable. I use a Briggs and Stratton one that you see an arc in the window. When you pulled the ground wire did you pull it from the coil end? Have you changed the plug? I have seen new plugs arc outside the cylinder but won't under compression.

Jeremy

 

[mdavlee]

Sounds like a bad coil.

 

[TexasTimbers]

Have you pressure and vacuum tested the saw yet?

I left the pressure gauge on for 30 minutes and it held 150 psi.

Are you using a spark tester with a little bulb in it

Yes the Lisle is the one I am using. It sparked when the saw started the one time and has not sparked since, and the saw hasn't started since. Seems like it is giving a reliable info to me. This one:

When you pulled the ground wire did you pull it from the coil end? Have you changed the plug?

Yes and yes.

I'm going to order a coil today.

Are the $25 aftermarket coils reliable? Does anyone know?