# Tecumseh - No spark



## T3KN1ne

Hi everyone,

Since the beginning of winter, I've been trying to start my snowblower with no success at all. Been looking here and there on forums, but there's something wrong that I can't quite put my finger on.
Maybe some of you can help, it would be really appreciated!

What I've done so far:
Looked for spark = No spark
New spark plug, new coil, new points gapped at .020 (actually a little tight with a .022 gauge), new flywheel key (the old one was strange)
Magnets on the flywheel are glued or welded and have some space between them, they seem to have enough power (test with screwdriver)

Still have no spark. I even tried to test the spark on the base of the engine, just in case, because I was told that there could be some carbon build-up between the head and base that could prevent spark from happening.

Since I've worked on many different stuff, I fear that I might be the one that did something wrong... Even if I can repair cars, I'm not used to that points system and magnetic flywheel.

By the way, It's an Ariens snowblower with a 10HP HM-100 Tecumseh engine.

Any help would be appreciated, Thanks!


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## bw77

I recently had a no spark condition on a Craftsman 28" snowblower with a 9hp Tecumseh Snowking engine. 

Turned out that the plastic key had come loose, probably from vibration.
Pushed it in and all is well.


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## Shryp

bw77 said:


> I recently had a no spark condition on a Craftsman 28" snowblower with a 9hp Tecumseh Snowking engine.
> 
> Turned out that the plastic key had come loose, probably from vibration.
> Pushed it in and all is well.


If he has points he doesn't have a plastic key.

It is possible that there is an issue with one of the electrical interlock safety systems. Try disconnecting all the extra wiring for the kill switch and then check for spark.


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## T3KN1ne

Yeah I forgot to mention, last year I had to replace the engine, and I didn't wire back the killswitch to the engine. So It's pretty much independant, no wire is going from the coil to the kill switch.

The only thing I didn't replace is the condenser, but I was told that I should have spark even without it, so I removed it and still no spark.


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## HCBPH

*No spark*

Change the condensor, had a no spark last year with everything else looking good - new points and condensor fixed it.

Other thing is confirm your points are opening and closing as they should (assuming it's not electronic ignition - points were mentioned earlier).
That's where I'd start then go from there.


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## T3KN1ne

Ok I'll look to buy a new condenser.

About the points, I can see them open and close while turning the shaft.
But I was wondering how it does actually work. It might help me get through that problem.

The way I've seen it, they seem to be closed most of the time, and opened at a short period of time. With what I've tested, I guess that when it's closed it shorts the electricity to ground, and when they open, this is when the spark goes to the spark plug.
Am I right?

Thanks for you input and help, hope to see my problem resolved in the next days/weeks.


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## HJames

You will notice that the flywheel shaft has a mounded area, this acts as a cam to open the points.Check to make sure the points have the proper gap. Very tempermental system, prone to incidental shorts and grounds if everything isn't installed properly and in good working order. I agree with HCBPH, switch out the condensor and double check everything before you reassemble the flywheel. The slightess ground or arc can steal your spark.
Check out the like below for an explanation of how it works.



http://www.briggsandstratton.com/us/en/support/faqs/ignition-system-theory-and-testing


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## T3KN1ne

Thanks, I'll look into it right away


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## T3KN1ne

Great info! I followed some of the stuff they said.
It seems that my new coil doesn't have the same impedance than the old one, but both have more than what Briggs and stratton said it should.

I've put it all back together, rechecked everything, tried to turn the engine and there was spark. Seems to be some great news for sure!
Tried to make it run, but no luck at all, it would'nt even do some explosions.

I removed the spark plug and checked for spark, it was fine. The only thing I would say is that the connector provided with the new coil doesn't seem to fit quite right for the spark plug, so it's a bit loose...

There didn't seem to be any gaz on the spark plug. But I could tell gaz goes to the carburetor because it was leaking when I primed it...

Any idea?

Thanks guys!


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## td5771

if the coil is outside the flywheel not under it, did you gap the coil?


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## T3KN1ne

No, it's Under. So the only think I could do is change the timing, since there are 2 bolts in round slottet holes.

I'll get a spark tester tomorrow, just to make sure that my spark is strong enough.

But I'm guessing there is a problem with the carburetor, because there was no gaz on the spark plug, even after several attemps of starting it.

I just don't want to remove everything if not necessary.


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## db9938

You did make mention that the flywheel key looked odd. By chance did it appear to look like a tapered "L?"

I have ran into this with vertical shaft tecumsehs, and yes that would impact your timing.


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## micah68kj

db9938 said:


> You did make mention that the flywheel key looked odd. By chance did it appear to look like a tapered "L?"
> 
> I have ran into this with vertical shaft tecumsehs, and yes that would impact your timing.


I do know that if the key has the *slightest* damage the engine will have spark, the plug will be wet......and it *will not run.*


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## db9938

True, but he also made mention of magnets, I was not sure if he meant under the flywheel and they fed the generator/alternator... 

I guess I should have asked. The one I was referencing, had a generator, and the tapered "L" shaped key.


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## HJames

*I've put it all back together, rechecked everything, tried to turn the engine and there was spark. Seems to be some great news for sure!*
*Tried to make it run, but no luck at all, it would'nt even do some explosions.*

So now you have spark. This is a good start!!

*I removed the spark plug and checked for spark, it was fine. The only thing I would say is that the connector provided with the new coil doesn't seem to fit quite right for the spark plug, so it's a bit loose...*

This could cause the spark to weaken but I would spend more time tending to the lack of gas in the chamber you mention below.

*There didn't seem to be any gaz on the spark plug. But I could tell gaz goes to the carburetor because it was leaking when I primed it...*

Could just be that you pushed the primer a few to many times or....something is plugged up in the carb and the gas is backing up somewhere. I would drop the bowl and give the jets a cleaning. Pop it back on and see if you can get it to try to fire. If it does want to fire but won't start, you will want to do a full carb clean.


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## T3KN1ne

Yeah by the way, I changed the flywheel key. The new one is different, but the old one (wich was taper) didn't seem to really lock the flywheel in the right position.

Anyway, this one was so tight that I had to sand it a little to make it fit.

Now I did a complete carburetor clean-up... Thanks to youtube!

The gas leaking seems to me like the small needle bushing for the float)
It seemed a little bit worn. Could that be the cause?

After the clean-up, I tried to start it, but still no luck. After, I checked the plug, it was wet. So what I did kinda worked.

I could hear some explosions like it wants to start but is timid. I even saw some explosions coming out of the carburetor... What could be the cause?

I'm thinking about timing, or air/fuel mixture? I put the adjustements bolts to "factory" Fuel: 1 1/2 turn out, Mixture: 1 turn out.

What do you think?
Thanks!


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## db9938

It is firing, before the intake valve is closed. That sounds like one of two things: a valve timing situation, or an intake valve clearance situation.


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## T3KN1ne

All I can say is that last year it worked totally fine until the end. 
So how could it be mechanical??


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## Colored Eggs

I would start with the carb. Its quite possible that its getting way to much fuel. Also if your needle is worn out it should be replaced including the seat as that is what governs the level of gas in the carb bowl and if that is flooding than it could be getting to much gas. Had an engine that the needle was not sealing correct and it flooded the engine completely but its a bit difference in a snowblower as usually the carb is below the intake and the fuel would rather just run out the other side of the snowblower.


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## T3KN1ne

Colored Eggs said:


> Had an engine that the needle was not sealing correct and it flooded the engine completely but its a bit difference in a snowblower as usually the carb is below the intake and the fuel would rather just run out the other side of the snowblower.


Exactly. You got a good point, since I'm pretty sure my needle is good but the bushing where it seats seems worn...
BUT, like you said, it is leaking out of the carb instead of flooding the cylinder because of the elbow going up to the engine.


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## T3KN1ne

Today I wanted to see if it can fire with carb cleaner. And it did, so it tells me that it could do some explosions with gaz. There might be too much of it, so like you said, I'll get a carb rebuilt kit. See if it helps...

But while doing my little test, something strange happened (sound as if engine was seizing, but it didn't) and the shear key broke.

It's beginning to make me sick. I'll soon get it to a Professional if I can't get to solve the problem...


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## Colored Eggs

If the Flywheel key sheared than it could be the timing/ valive problem. However it could also be to much gas/carb cleaner. I would get the carb fixed first then take the spark plug out and let any gas or vapors inside escape so that you can rule out the carb as causing the key to break.

However..... was the key broken the first time as well? If so It could be an internal issue as this is the 2nd time it has done it.


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## micah68kj

I think I'd toss, no, fling that engine from a very tall bridge or fix it with a blasting cap.


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## Shryp

If the flywheel key broke that means you didn't have the flywheel tight enough.


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## micah68kj

Shryp said:


> If the flywheel key broke that means you didn't have the flywheel tight enough.


Which would explain a lot of the other symptoms come to think about it.


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## T3KN1ne

Yes I think you're right.

The key I bought at a small snowblower shop didn't seem to fit (in size) in the slot... Even if I gave them my engine number...

So I had to modify it a bit, and it seemed to get too tight in the flywheel. That's why it didn't sit deep enough and was maintained more by the key than the taper and nut.

With the new key, everything is great. Except, still not working.
I am being followed with a guy on Internet, I paid for, to make it work...

But still no luck... I have spark, carb is repaired now with new needle and seating. So no more leak.

Compression is 90 psi. Wich gets higher with a little bit of oïl in the cylinder. Around 100. Doesnt seem good.

I'm not far from recording myself while I tear it to pièces and put it on youtube


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## T3KN1ne

And here I am again, not giving up on my engine...

I've found by doing a leak down test, that both intake and exhaust valves are leaking badly. Doesn't even hold compression at all.

I tried lapping both valves, and check the gap at TDC. Everything seems good to my eye. I have .008 for both intake and exhaust. Might not be enough for exhaust regarding to specs, but should still work.

I bought new valves, but not sure it would make any difference. The seatings look good, and after having lapped them there is a good 3/32 wide circle on the seat and the valve.

Should I still try the new valves?


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## ranvette

I would use the valves in there and make sure the clearance is well in spec.Than redo the leak down test.That way you will know 100% you dont have a ring problem before fully reassembleing things.


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## micah68kj

You have *way more patience* than I ever had. I'd 'a flang that thing from a very tall bridge by now. Still hoping to hear some good news after all your effort though.


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## T3KN1ne

ranvette said:


> I would use the valves in there and make sure the clearance is well in spec.Than redo the leak down test.That way you will know 100% you dont have a ring problem before fully reassembleing things.


Yeah I'll do it again just to make sure, but I've done it twice already, so I doubt it will change anything.

How can I be sure that the rings are good? I can feel air coming out of intake and exhaust valve, but if it was sealed, it could pass the rings if they were done.

Maybe I don't understand exactly what you mean


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## T3KN1ne

micah68kj said:


> You have *way more patience* than I ever had. I'd 'a flang that thing from a very tall bridge by now. Still hoping to hear some good news after all your effort though.


Haha thanks! I'm more stubborn than patient for sure!
I've given up a thousand times, but can't let it go. This engine has to be working no matter what.


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## T3KN1ne

So I've replaced both valves, lapped them.

Ran leak down test. They are sealing well now, but it's leaking from the piston. Seems like I will have to order rings...

I'm just wondering: With the new valves in, my clearance at TDC is too high. Is there something I can do about it?


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## micah68kj

T3KN1ne said:


> So I've replaced both valves, lapped them.
> 
> Ran leak down test. They are sealing well now, but it's leaking from the piston. Seems like I will have to order rings...
> 
> I'm just wondering: With the new valves in, my clearance at TDC is too high. Is there something I can do about it?


Cut/grind them just a mite? I honestly don't know, never having had that problem.
Seriously, I really admire your persistence. You got props man.


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## db9938

I've used a fine honing stone, to limit the amount of material removed at any given time. Just make sure to wipe it down well. Of course, it depends on how much material that needs to be removed, and make dan sure you keep it perpendicular.


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## T3KN1ne

Well I haven't measured it yet, but it looked to my eye a little bit more than 1/32. I'm not sure if I understand well what you're saying.

It seems to me, if I want to get a smaller clearance I would have to either remove material on the valve so it can go deeper in the engine or remove material on the block itself.

Might be hard to do since it's not flat, but since it's the seating of the valve there might be something like a 45 degree angle...

I'm guessing they sell a special tool for that. who knows?

I'll call the shop where I bought the valves, to see what they can do about it.


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## Grunt

T3KN1ne said:


> It seems to me, if I want to get a smaller clearance I would have to either remove material on the valve so it can go deeper in the engine or remove material on the block itself.I'm guessing they sell a special tool for that. who knows?


 You are correct, the valve seats would have to be recut with a special (expensive) tool. I'm surprised that there is so much clearance if you bought "new" valves which usually need to be filed (shortened) for correct clearance. Lapping the valves may help.


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## nt40lanman

Don't worry TOO much about the rings. Valves should always seal but rings seal better when they warm up. Try a compression test, then a little oil in the cylinder and do it again.


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## T3KN1ne

Grunt said:


> You are correct, the valve seats would have to be recut with a special (expensive) tool. I'm surprised that there is so much clearance if you bought "new" valves which usually need to be filed (shortened) for correct clearance. Lapping the valves may help.


 Yeah, so it's not really an option. I might try to get another valve from the shop, since the intake one is almost perfect. Both exhaust valves have the same lenght but the new one has a thicker head.



nt40lanman said:


> Don't worry TOO much about the rings. Valves should always seal but rings seal better when they warm up. Try a compression test, then a little oil in the cylinder and do it again.


 Ok. Good to know. I'll do it and post back the results. I had 90 psi top before the valve replacement.


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## Grunt

Have you tried lapping the old or new valve so the angle of the seat and valve match each other. A hand lapping tool and paste are under $10. If the compression test showed 90 psi, the compression release is not working because of the increased valve clearance. I thought 50 to 60 psi on an engine with the compression relief working was about normal. I could be and probably am, wrong.


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## T3KN1ne

Well, I have lapped the old valves more than once with no result at all...

My gap with old valves was near to be fine, might need a little fine tuning.
The compression release works good too.
But with the new valves, of course it doesn't work, the clearance is too high.

About the compressions test, I was told that below 100 psi, it's not really good.


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## ranvette

You are correct around 50psi or so is normal compression.With compression release working properly.I have Strong 6 and 8 HP Tecumseh L heads and thats what they put out.


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## T3KN1ne

Wow Ok.

I've tested compression today with the old exhaust valve, and I have 120 PSI now. How is that possible?
I can see the compression release pin pushing the exhaust valve up and down.

I retried to start it, just in case, but nothing at all.

I just can't understand why it won't even try to start, it would help me figure out what's the problem...


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## Shryp

I am not sure how the compression release works on these engines, but I do know from watching the donyboy73 videos on lawn tractors with OHV engines the compression release will stop functioning and stall the starter motor if the valves are not properly adjusted.


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## ranvette

Well first step is get the clearances were they need to be i would say


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