Ariens Briggs & Stratton won't start.

Richard Milhous

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Visibly that will check for spark. But is it enough to fire across the gap under compression? No way of telling with a timing light.

Either gap a plug to 1/4" or 6mm or get a real tester like the one below.

An inductive pickup won't trigger consistently on a really weak spark. You're right it doesn't actually prove the spark is strong enough, but it's usually right and easier to use than pulling and ground the plug. At least if you have a 12V battery handy to power it.

...and you can always have current discharge without actual spark, if the plug is bridged or the insulator is cracked.
 

Richard Milhous

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Slomo is right about the plug wire insulation. If it's weak in some spot, it might be partially shorting out to adjacent metal but if you move the wire to test the removed plug, it might no longer be adjacent to metal there. It's also possible (but very unlikely unless it's old and abused) that the conductor in the plug wire has a break.

How large was the gap between electrode and nut when you saw spark? If it was 1/4" and you saw a bright spark, that's great. If it was 1/10" and just a flicker, not so great. It's a pain to ground the plug body and I don't know if I'd reuse a plug after gapping it to 1/4" (!) but Slomo's test is a definitive one. With the possible exception of a position-dependent flaw in the plug wire.
 

D_H

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Visibly that will check for spark. But is it enough to fire across the gap under compression? No way of telling with a timing light.

Either gap a plug to 1/4" or 6mm or get a real tester like the one below.
I can't justify the investment of that Oppama PET-4000 or the Echo equivalent. So you're suggesting that I open up a good spark plug to 1/4" or 6mm and try to fire the motor again without holding the spark plug boot. That's difficult as there is not really anywhere to rest or wedge the spark plug and cable on. I'll see what I can do. By widening that spark plug gap will determine if my ignition coil is providing enough giddy-up to the spark plug?
Check the oil dipstick and smell for fuel.
I checked the oil dipstick and did not smell fuel on it. The oil appears okay to me.
I would stick with the ol' tried and true SAE30 oil. Briggs says 5w-30 will consume more oil and to check the level more often. Don't have to do that with SAE30 oil.
Yes, I agree. I had a hard time finding the SAE30 at the time and the manual said that this 5w-30 synthetic would work just fine. I did check it though before every mow. A little more than every other time it would need to have some oil added to become within tolerance. It also blackened up quite a bit faster than the SAE30. I think it came factory filled with B&S SAE30 and that's proven to be good oil over the years. That's what I'll be using in the future from now on.
 
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Richard Milhous

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I can't justify the investment of that Oppama PET-4000 or the Echo equivalent. So you're suggesting that I open up a good spark plug to 1/4" or 6mm and try to fire the motor again without holding the spark plug boot. That's difficult as there is not really anywhere to rest or wedge the spark plug and cable on. I'll see what I can do. By widening that spark plug gap will determine if my ignition coil is providing enough giddy-up to the spark plug?

I checked the oil

Yes, I agree. I had a hard time finding the SAE30 at the time and the manual said that this 5w-30 synthetic would work just fine. I did check it though before every mow. A little more than every other time it would need to have some oil added to become with in tolerance. It also blackened up quite a bit faster than the SAE30. I think it came factory filled with B&S SAE30 and that's proven to be good oil over the years. That's what I'll be using in the future from now on.
dip stick and I can not smell any fuel. The oil appears okay to me.

One thing you could try is putting the plug in the jaw of a jumper cable and clamping the other end of the cable to whatever metal you can find on the block.

I dunno why SAE 30 is so hard to find now but it's a pain. I've been using 10w30.
 

D_H

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Slomo is right about the plug wire insulation. If it's weak in some spot, it might be partially shorting out to adjacent metal but if you move the wire to test the removed plug, it might no longer be adjacent to metal there. It's also possible (but very unlikely unless it's old and abused) that the conductor in the plug wire has a break.

How large was the gap between electrode and nut when you saw spark? If it was 1/4" and you saw a bright spark, that's great. If it was 1/10" and just a flicker, not so great. It's a pain to ground the plug body and I don't know if I'd reuse a plug after gapping it to 1/4" (!) but Slomo's test is a definitive one. With the possible exception of a position-dependent flaw in the plug wire.
The plug wire insulation appears fine to me. The only wear/abuse I can see is from me taking the spark plug out several times. The boot now has some small cracks in it. That's it other than some light dirt/dust on it.

I am not sure how large the gap was when I held the boot and tested spark against a screw. I was not aware I needed to be precise. I'll have to go try it again. I bought a few plugs and am willing to sacrifice one to do the 1/4" or 6mm test. If it helps me get to a running mower again, it's a small price to pay.

Are there any thoughts on this whole thing being some type of safety deactivation switch problem? I mean it just died. Just to reiterate, I'm driving it a short distance across the drive (blades not engaged) and it just died. It died just like if I was riding it and then stood up, lifting my butt off the seat without it in park. Now when I try to start it, it acts just like I am trying to start it without the mower in park or am starting it while not sitting on the seat.
 

Richard Milhous

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Safety devices work by cutting the ignition (or sometimes starter current) so that ain't it.

You can't reliably judge plug wire insulation visually (unless it has been plumb rotted off by oil). If you don't have a pacemaker you can try grabbing it while the motor cranks.
 

bertsmobile1

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Back on planet earth
SO you have confirmed that there is a spark that should be happening at the right time
The engine will not fire with a fuel that is far more volatile than petrol put into the combustion chamber through the plug hole.
So that tells us you have a valve / piston problem.
So next step in diagnosing is to put a pencil down the plug hole and check that there is a piston in there that is moving .
Once you have confirmed that take off the rocker cover & spark plug
rotate the engine at least 2 full rotations while watching the rockers moving
The valves & guides are identical so they should sit at exactly the same height and go in & out the exact same amount
When the piston is in the firing position both vlaves should be closed and there should be some slack between the ends of the rockers & the top of the valve stem.
 

slomo

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One thing you could try is putting the plug in the jaw of a jumper cable and clamping the other end of the cable to whatever metal you can find on the block.

I dunno why SAE 30 is so hard to find now but it's a pain. I've been using 10w30.
Walmart has it at 10 bucks a gallon. It's also SG rated and full of ZDDP zinc anti-wear gooo.

 

slomo

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I can't justify the investment of that Oppama PET-4000 or the Echo equivalent. So you're suggesting that I open up a good spark plug to 1/4" or 6mm and try to fire the motor again without holding the spark plug boot. That's difficult as there is not really anywhere to rest or wedge the spark plug and cable on. I'll see what I can do. By widening that spark plug gap will determine if my ignition coil is providing enough giddy-up to the spark plug?
The PET-4000 is expensive but the best tool for this purpose.

Runner-up is a cheap spark plug opened to 1/4". Use insulated Channel Lock pliers if you are getting shocked. And if you are getting shocked, I would take some good electrical tape and wrap up your plug wire, all the way to the coil. Or use some butyl rubber tape. Or wear a thick glove and hold the plug to the engine block checking for spark.

Take insulated pliers. Hold the 1/4" gaped plug against the engine block on clean unpainted metal. Crank the engine over looking for spark.

Widening the gap simulates a LOAD on the coil. Same as a running engine. Not just oh I see a small light bulb turn on inline tester job does.
 

slomo

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Safety devices work by cutting the ignition (or sometimes starter current) so that ain't it.

You can't reliably judge plug wire insulation visually (unless it has been plumb rotted off by oil). If you don't have a pacemaker you can try grabbing it while the motor cranks.
Just a tiny imperfection in the wire insulation can get you nailed. Summertime sweaty hands are no good too LOL.
 
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