Husqvarna 268 I'm puzzled

[JT78]

Ok so I rebuilt this saw a couple months back and it's been running like a top for the tree company I rebuilt it for. The saw lost spark so it came back to me. I checked it over and everything looks good except there was no spark. So I ordered a coil and changed it out and it has good solid spark now. Piston and cylinder look good and saw is getting fuel but it won't start. I'm very puzzled it's got compression, fuel, and fire now but it will not start and run. I checked the flywheel to make sure it didn't spin on the crank but it's still in place with the key.

Any ideas on what I could be missing ?

 

[Maintenance Chief]

Some bad spark plugs have done this to me.

 

[Wood Doctor]

Carburetor is not supplying the correct fuel mixture or not supplying sufficient fuel. You may also have lost compression. That's the bone crusher.

 

[drf256]

Could the coil be wrong? Sometimes they produce different timing in same physical position.

 

[farminkarman]

Ok so I rebuilt this saw a couple months back and it's been running like a top for the tree company I rebuilt it for. The saw lost spark so it came back to me. I checked it over and everything looks good except there was no spark. So I ordered a coil and changed it out and it has good solid spark now. Piston and cylinder look good and saw is getting fuel but it won't start. I'm very puzzled it's got compression, fuel, and fire now but it will not start and run. I checked the flywheel to make sure it didn't spin on the crank but it's still in place with the key.

Any ideas on what I could be missing ?

Is the coil an OEM replacement or an AM piece?

 

[drf256]

I have a 2 piece 266 oem coil.

 

[Czed]

Try priming it with mix in the carb
just to see if your getting enough fire.

 

[Funky sawman]

I've had brand new oem and aftermarket ignition modules show spark when testing with plug out of saw, but under compression it takes more voltage to jump the gap, so they would fail to fire. Test spark with spark plug in head and tester in-between plug and module wire

 

[Stump Shot]

If the plug is fowled but good, it may need replaced to get it to fire. Sometimes cleaning it with compressed air will do the trick on a wet plug and sometimes not. Sever cases you may have to "clear" the engine out of fuel out the spark plug hole by rolling the engine over, careful with the plug wire end as a fire can be started quite easily doing this kinda thing.
Otherwise as mentioned it needs to fire across a 5 to 6mm gap and be a bright blue in color when doing so. Also primary and secondary compression need to be proper as well. Sometimes it's easiest to cut to the chase and pop the muffler off to take a peak at the piston condition, especially without a compression tester.

 

[Agrarian]

If the plug is fowled but good, it may need replaced to get it to fire. Sometimes cleaning it with compressed air will do the trick on a wet plug and sometimes not. Sever cases you may have to "clear" the engine out of fuel out the spark plug hole by rolling the engine over, careful with the plug wire end as a fire can be started quite easily doing this kinda thing.
Otherwise as mentioned it needs to fire across a 5 to 6mm gap and be a bright blue in color when doing so. Also primary and secondary compression need to be proper as well. Sometimes it's easiest to cut to the chase and pop the muffler off to take a peak at the piston condition, especially without a compression tester.

5 - 6mm gap??? 0.200" - 0.240"? The spec is only for 0.020" (0.5mm). What am I missing?

Another possibility is an intermittent connection in the plug wire.

 

[drf256]

5 - 6mm gap??? 0.200" - 0.240"? The spec is only for 0.020" (0.5mm). What am I missing?

Another possibility is an intermittent connection in the plug wire.

Probably a typo. Noone thinks 1/4” acceptable.

So you get no pop at all if prime through carb bore?

Sounds like you have the basic 3, fuel/comp/spark. You checked flywheel, so spark should be at right time. But, for example, the 3120 has 2 different coils and flywheels. Adding a 272 coil to one that came with a black oem coil will not work. Flywheel needs to be rebroached almost 90* from original. But, if you have the newer 3120 (like I do) its plug and play. And thats with the coil being bolted in same exact position.

If the coil isnt exact, it may be timed way off, even in same position.

 

[drf256]

Also, if flywheel took a hit, magnets could have changed polarity. This will cause no spark. Ive had it happen.

At least with the 266, they had a 1 or 2 piece coil setup IIRC.

Your plug lead could be bad as well. Also, the top spring that holds the plug could be fractured.

 

[Stump Shot]

5 - 6mm gap??? 0.200" - 0.240"? The spec is only for 0.020" (0.5mm). What am I missing?

Another possibility is an intermittent connection in the plug wire.

Not to set your plug gap, a spark test(er) should be this length as to mimic the spark strong enough to fire under compression, which is much harder to do than out in the open air. Again, this is just for testing purposes only.

Probably a typo. Noone thinks 1/4” acceptable.

No typo, not a good clarification of what I was trying to lay down.

 

[Gord]

Had a 390xp in the other day, -sort of ran, if you looked at the plug in an upright position looked great but if you turned it down the gab closed, seen it more than once, porceline broken inside. Probably not your problem but could have been messing with that saw for quite a while, put a smile on the owners face when that was all it was.

 

[drf256]

Not to set your plug gap, a spark test(er) should be this length as to mimic the spark strong enough to fire under compression, which is much harder to do than out in the open air. Again, this is just for testing purposes only.

No typo, not a good clarification of what I was trying to lay down.

Ahh. I read it wrong too.

After spending $300 and many hours on a Honda GX engine, replacing the $2 plug first became my SOP. Bright spark outside engine too.

 

[Stump Shot]

Ahh. I read it wrong too.

After spending $300 and many hours on a Honda GX engine, replacing the $2 plug first became my SOP. Bright spark outside engine too.

I should have been more articulate, most likely from still being on my first cup of coffee of the day.

 

[slackinoff]

When you say it has fuel, how did you determine that? Don't assume anything (as in it had fuel before spark was lost) - Could be a cracked intake block screwing up the pulse going to the carb to run the diaphragm pump, or a bad gasket set on the intake block.

Another thing to check is worn throttle shaft sucking air. I have had that happen twice building these saws.

Any of those issues would still allow the saw to pop off though if you squirted fuel down the throat or spark plug hole and yanked it....have you tried that?

 

[Czed]

Try priming it with mix in the carb
just to see if your getting enough fire.

Bump

 

[Czed]

Bump

Bump

 

[JT78]

Haven't had time to get back to it yet, I used a spark plug tester it's getting a strong spark. I peaked through the spark plug hole and can tell that the cylinder looks nice and clean no scoring. I know it's getting fuel as the plug is wet I'm thinking maybe it's getting too much fuel but I tried turning the carb screws all the way in with fuel in the cylinder and the saw still won't pop. I'm thinking that the coil is firing at the wrong time. I will start checking more tomorrow when I'm off work.