# Saw has spark, compression, and gas but won't run.



## ChainLightning (May 29, 2012)

Saw is a Jonsered 2045. I got it for mowing a friends lawn. Took it home and put gas in it and she wouldn't even so much as fire so I tested it for spark. Had a nice bright blue spark. So I then took off the carb and cleaned it. Everything was there, clean, and set up right so I slapped that back on. Still nothing. I took some starting fluid and put it down the spark plug hole (Could not put it down the air cleaner without tearing the whole thing apart) and still nothing. 
I figured then that the plug might be bad. Just because it sparked out of the saw, did not mean that it could spark under compression. (BTW the saw has great compression) So I looked up the right plug (old one was right) and put it in. Still nothing. Even with starter fluid. This time I pulled the whole carb and air cleaner assembly off and sprayed some down in the intake. when you pulled it and you could see it do was mist back out. No I DID NOT flood it on any of these starting attempts. 
I am have no clue what is wrong with this saw. I have only seen one other saw do this before and that was a Poulan Wild Thing that a friend gave me. I threw it away because I was done with it.  I was thinking of a sheared flywheel key but not sure. What do you think.


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## Somesawguy (May 29, 2012)

It could be a flywheel key. If the timing is off, it won't fire.


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## WKEND LUMBERJAK (May 29, 2012)

Try a plug from a known running saw some times new plugs are bad.


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## elwoodps (May 29, 2012)

I'm not sure about your starting problem, but you really should be careful with the starting fluid in mixed-gas engines. It not only provides no lubrication, but it's also an extremely powerful degreaser.


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## ChainLightning (May 29, 2012)

elwoodps said:


> I'm not sure about your starting problem, but you really should be careful with the starting in mixed-gas engines. It not only provides no lubrication, but it's also an extremely powerful degreaser.



I know. I usually try to keep it to a minimum. A lot of people use that stuff like gas. I know how much a pain it is to change a scuffed up piston or bad rings. No fun.


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## zogger (May 29, 2012)

Timing, or mud dauber nest or blocked screen in the muffler


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## komatsuvarna (May 29, 2012)

I was working on a friend 038 that was getting every thing to run, just wouldn't run. It had a nice blue spark that looked great to me. I swapped parts and swapped parts and finally took the coil off my 460 and bolted it up on the 038. Bamm, First pull and it fired. I even swapped them back to be sure. Kinda threw me for a loop since it appeared to have nice spark, but a different coil fixed it. 

Just a thought.


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## CTYank (May 30, 2012)

What, precisely, is the "starting fluid" mentioned? How about a couple of drops of fresh mix?


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## Stihlofadeal64 (May 30, 2012)

Starting fluid is a "no no" for 2 cycle engines. If you didn't know before you do now. Just drop some mix into it and that will suffice. No need in trashing the saw over a simple mistake.


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## Arrowhead (May 30, 2012)

Somesawguy said:


> It could be a flywheel key. If the timing is off, it won't fire.





WKEND LUMBERJAK said:


> Try a plug from a known running saw some times new plugs are bad.





zogger said:


> Timing, or mud dauber nest or blocked screen in the muffler



All my thoughts also. I've had plugs sparking fat blue sparks outside the saw, but wouldn't fire under compression. Swapped plugs and saw runs.


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## o8f150 (May 30, 2012)

the other guys are right,,the next thing to check is the spark screen,, if that is ok, pull the fly wheel to check the key,


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## Cantdog (May 30, 2012)

zogger said:


> Timing, or mud dauber nest or blocked screen in the muffler




HaHaHa!! Funny you should mention mud daubers!! I have a 2045 that someone gave me...well used and had been sitting quite a spell. First thing I did was pull the muffler to check out the piston and see if there even any point to go further. The EX port was full of mud daubers!!! No way to get rid of them without pulling the cyl and of course being a clamshell meant the entire saw had to come apart...it's still sitting in a box all cleaned up and waiting until I have to order a bunch of parts for other stuff as it needs a new ring and impulse nipple, carb kit etc.


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## nmurph (May 30, 2012)

I'm betting it's flooded...OP, I know you said it's not, but pull the plug, pull it over about 30x's, let it sit with the plug out and give it a couple of pulls every once in a while during the day. Then use the old match in the cylinder trick just to make sure you have it de-gassed. Then re-install a new plug, dribble in a little mix, and see if it doesn't start.


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## woodyman (May 30, 2012)

After new plug,cleaned muffler,rebuilt and adjusted carb,all rubber parts,connections and fittings checked,flywheel key checked,coil gap checked,on/off switch working,air filter clean and spark.Could be coil,it's not rocket science,or is it:hmm3grin2orange:Most of the time it's fuel related but I have had 3 saws that needed coils in the last year.I say coil if all the other things have been checked.I see saws on fleabay that say"runs on starting fluid"I stay away from them.


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## Dan_IN_MN (May 30, 2012)

nmurph said:


> I'm betting it's flooded...OP, I know you said it's not, but pull the plug, pull it over about 30x's, let it sit with the plug out and give it a couple of pulls every once in a while during the day. *Then use the old match in the cylinder trick just to make sure you have it de-gassed.* Then re-install a new plug, dribble in a little mix, and see if it doesn't start.



Make sure you don't have gas on your hands when you do this! I learned that very early on when I was around 15 or so. Not fun!

Is the plug wet when you take it out?

How much compression does it have? Check it with a gauge.


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## nmurph (May 30, 2012)

manyhobies said:


> Make sure you don't have gas on your hands when you do this! I learned that very early on when I was around 15 or so. Not fun!
> 
> Is the plug wet when you take it out?
> 
> How much compression does it have? Check it with a gauge.



I had a "friend" that broke into the school bus yard to steal gas...you guessed it, he lit a match to see how much he had siphoned out. He got lucky and only got minor burns and lost some hair...unfortunately, he never lived a sober life and died in his early forties of cirrhosis of the liver...some people never learn.


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## ChainLightning (May 30, 2012)

nmurph said:


> I'm betting it's flooded...OP, I know you said it's not, but pull the plug, pull it over about 30x's, let it sit with the plug out and give it a couple of pulls every once in a while during the day. Then use the old match in the cylinder trick just to make sure you have it de-gassed. Then re-install a new plug, dribble in a little mix, and see if it doesn't start.



Ill have to give that a try. I checked the muffler screen and it was clean. The piston was scuffed up quite a bit on the muffler side, but is fine on the intake side. Still has great compression tho. What does the match do? just get it warmed up?


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## Dan_IN_MN (May 30, 2012)

ChainLightning said:


> Ill have to give that a try. I checked the muffler screen and it was clean. The *piston was scuffed up quite a bit on the muffler side*, but is fine on the intake side. Still has great compression tho. What does the match do? just get it warmed up?



The fire is a way to burn out the excess fuel out of the cylinder. (to be used with extreme caution!)

I'm betting the compression isn't that great and is the reason why it's not running. Been there tried that! A compression gauge is your answer.


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## naturelover (May 30, 2012)

If you have compressed air handy, that can be used as a quick, safer alternative to the match method...


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## powerking (May 30, 2012)

Whats your definition of "good compression"?


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## ChainLightning (May 30, 2012)

powerking said:


> Whats your definition of "good compression"?



Where your arm gets tired after pulling it 5 times.  But seriously I have worked on many many saws before and I can feel if it has good compression.


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## nmurph (May 30, 2012)

naturelover said:


> If you have compressed air handy, that can be used as a quick, safer alternative to the match method...



While safer, it isn't nearly as much fun.:cool2: It also only removes the fuel fumes whereas the flame gets excess liquid. I have been doing it for years. If someone isn't comfortable doing this way, I certainly understand and they should opt for other methods. I certainly wouldn't do it to a carburated car, but the mix that two strokes burn isn't quite as flamable as pure gas.


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## nmurph (May 30, 2012)

ChainLightning said:


> ...The piston was scuffed up quite a bit on the muffler side...



That's a pretty important tidbit of info. Again, your saw is likely flooded bc it lacks sufficient compression. The fuel is being pulled in but the saw isn't running and burning it.


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## ncfarmboy (Jun 1, 2012)

ChainLightning said:


> Where your arm gets tired after pulling it 5 times.  But seriously I have worked on many many saws before and I can feel if it has good compression.



You can not go by it feels like it has good compression! I fought a 670 Jred off and on for 6 mo. felt like it had excellent comp. Piston was clean looking in ex. port. Finally checked comp. 90psi not enough to run. Check compression with a guage your arm lies.
Shep


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