lawnmower coil problem?

[ProdigySBC_SUX]

I have a hand-start lawnmower that stopped running recently. It is a Briggs & Stratton, about 5 yrs old, and gets medium usage. It has given me no problems until now.

The cylinder appears to be getting a fuel/oil mix delivered but is not getting spark. I have pulled the plug, checked it for fouling and proper gap, and grounded out the 'outer' terminal of the plug while connected to the plug wire and not seen a spark when cranking the engine. Finally, I wound up jamming the tip of my little finger in the plug boot and while my thumb was grounded to the motor head cranked the engine. No pulses into my hand so unless somebody tells me otherwise, I am confident my primary issue is the 'spark'.

I removed the engine covers and see an electronic device similar to the device in the following link:

My flywheel looks almost identical to that though scaled up a bit in size. Soooooo........ I have read about coils elsewhere at that above link and am left with more questions (from more knowledge) than I started. I have checked the 'safety' aspects of the mower to be sure they are not intervening (the mechanism that breaks the circuit in case you release a lever up at the top of the handle that is required to be depressed during operation).

1) I read 4.5K ohm between the plug wire and the engine block.

2) I have very lightly sanded the track of the flywheel the travels under the coil poles(?) to remove some light rust on the flywheel and be sure the gap between the flywheel and coil was consistent.

Sooooo, unless you think otherwise, my guess is that the condenser/cap of the magneto/coil is bad. (It seems like I might still feel a little jolt at the plug wire - just not as much as normal - unless the cap is shorted out, but then wouldn't I read a short to ground from the plug wire?)

Anyway, thanks for your time if you have read this.

[bumtracks]

maybe make sure the dead short off mechanism that shorts the spark off isn't dead shorting while its in on position.

Stick a screw driver or nail in the plug holder and hold that near ground get someone to give it a good pull if you see or hear spark then you've just determined the spark plug is bad - still no spark from a nail get a new electronic coil module.

[AZGuy]

The last time I worked on one I found that it had a set of points inside a housing that was under the flywheel. That was quite a while ago and they might be all electronic now. But the fix on mine was to file and adjust the points, just like on an old car.

-- Elbridge Gerry, of Massachusetts:

"What, sir, is the use of militia? It is to prevent the establishment of a standing army, the bane of liberty. . . Whenever Government means to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise a standing army upon its ruins." -- Debate, U.S. House of Representatives, August 17, 1789

[Stormin Mormon]

More inserted.

[Stormin Mormon]

I've worked on a bunch of those. Point gap is .020 inches at the widest part of the cycle. They worked well for a lot of years. I can't remember when they went electronic, but it was at least five years ago.

[m Ransley]

The ignition module is a likely cause, test the coil first to rule it out.

[ProdigySBC_SUX]

'Walking' lawnmower.

4-cycle? Not sure - I don't have to pre-mix oil and gas. (see more below.)

I replaced the coil/ignition assembly and now have spark back at the plug. Unfortunately, it still won't start.

I have left the plug connected to the plug wire and grounded out the 'body' of the plug and seen what appears to be consistent and good spark when cranking the engine. There is fuel getting to the cylinder because I see it on the plug when I pull it after cranking. I can't understand why I would have two different failures at the same time. I am going to change my gas out and see what happens. (I usually run the mower off of the same oil/gas mix I run through the weedeater. One of the mechanics at a lawnmower shop suggested it and said the mower engine would actually last longer for it.)

Q: Even though I see the plug sparking when I pull the start rope, can a plug still be 'bad' and part of my problem? I think it is a Champion RJ19LM. The manual sez that in some places (e.g., CA) the plugs will have a resistor in them to reduce EMI emissions. If the place I am buying the plug has any idea whether the plug has a resistor I will try to get the non-resistor version.

My manual for my Ryobi line trimmer at least came with directions on how to adjust the carburetor but this manual for the Murray mower / B&S engine unfortunately doesn't have any such information. I'll start with a new plug unless people here feel that mine is good.

Thanks.

[m Ransley]

You are running 2 stroke mix in a 4 stroke, that will carbon up the motor. Your plug is wet and you have spark, so you are flooding it, Keep choke off and spray in some either. Or even at 5 yrs your compression may be to low to run it, test compression. Or a few other things.

[ProdigySBC_SUX]

Ok - all good info. I'll go chew on this for a while. I have had concerns the engine was getting flooded because the dang plug has been dripping sometimes when I pulled it. But here's the clincher about your advice with respect to this mower: In their effort to make it as idiot-proof as possible, I have no control over the throttle or choke.

Typically, I pull the CPSC (CPS?) lever, tie it down with some cord, push the priming bulb a couple of times, crank the engine 2-3 times, and go. I have no control over speed ot anything. Once I put the wheels in gear I can only disengage them by releasing the CPSC lever which also kills the engine.

[m Ransley]

It has to have a choke find its position-setting with respect to cable setting and try starting without or minimum choke. Plug or more could be bad you need a blue not yellow spark. Is air filter clogged. It is possible running 2 stroke you carboned up the valves and they do not seat anymore lowering compression to much to have power. But the right mix of gas and air and it should fire. Try Either in the carb with choke off.

[m Ransley]

Somewhere is a carb, choke, speed control. Look on the carburator.

[Mark]

yeah, air filter, that got me once, after working on an engine, I had it upside down for a while, the oil had dripped onto the air filter clogging it. I removed the air filter and it started right up.

Mark

[Stormin Mormon]

(Might have the answer... but it's on the bottom)

'Walking' lawnmower.

4-cycle? Not sure - I don't have to pre-mix oil and gas. (see more below.) CY: If it's got a dipstick and crankcase, that's a "4-cycle".

I replaced the coil/ignition assembly and now have spark back at the plug. Unfortunately, it still won't start.

I have left the plug connected to the plug wire and grounded out the 'body' of the plug and seen what appears to be consistent and good spark when cranking the engine. There is fuel getting to the cylinder because I see it on the plug when I pull it after cranking. I can't understand why I would have two different failures at the same time. CY: Might be just one....

I am going to change my gas out and see what happens. (I usually run the mower off of the same oil/gas mix I run through the weedeater. One of the mechanics at a lawnmower shop suggested it and said the mower engine would actually last longer for it.) CY: I can't comment on that, but it shouldn't hurt.

Q: Even though I see the plug sparking when I pull the start rope, can a plug still be 'bad' and part of my problem? CY: Yes, possible, but not very likely.

I think it is a Champion RJ19LM. The manual sez that in some places (e.g., CA) the plugs will have a resistor in them to reduce EMI emissions. If the place I am buying the plug has any idea whether the plug has a resistor I will try to get the non-resistor version. CY: Champion did have some quality problems.

My manual for my Ryobi line trimmer at least came with directions on how to adjust the carburetor but this manual for the Murray mower / B&S engine unfortunately doesn't have any such information. I'll start with a new plug unless people here feel that mine is good. CY: Saving the best for last. If you hit a rock, the flywheel keeps going. Shears a soft metal "key" and rotates out of tiem with the rest of the motor. On the older mowers, that means no spark. Cause the magnet on the flywheel is now out of time with the points. On the new electronic mowers, you stillg et spark. But it's out of time with the cylinder. The way to check is to pull the motor cover off the top. Take the big nut off the center of the crank shaft (hold the blade with your boot under the deck while you're cranking on the nut). Look down from the top. there should be a notch in the crank shaft, and a notch in the flywheel. And they should be at the same place. If the two notches aren't lined up, you need a new flywheel key. Which is a whole new adventure.....

Thanks. CY: Y'welcome.

[Stormin Mormon]

Plugs by AC or NGC have worked well for me.

Leave plug out, and give the ripcord a couple yanks -- tht dries things out within the cylinder.

[ProdigySBC_SUX]

See new thread.... Part II. Thanks for all your help.