20" Gas lawn mower runs for 20 min - stalls out

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What plug did you use? Briggs is notorious for using an emissions plug that flat out sucks on some engines. Replace odd part numbers with a Champion rc12yc.

It does sound like your ignition coil died.
 
Lots of CT people around here! As for the coil, find the correct part number and then check ebay. Ebay is usually much cheaper than a dealer of any type and even most of the online stores. Jack's small engine.com has good prices, accurate parts diagrams and is a good place alternative to a dealer.

Not sure what your budget is, but my Craftsman (Sears) and Toro (Home Depot) self propelled push mowers are over 10 years old and have never given me a problem, even with very minimal maintenance. They are basically the same exact machine, they both come with Briggs and Stratton engines and have all the features and power you could ever need in a push mower. A new one costs about $299. One machine, purchased once for $299 and lasting at least 5 (if not 10 or more) years works out to a huge savings over purchasing junk at $168 every year. In other words, Unless you really like troubleshooting and diagnosing, I would fix yours, sell it and then buy yourself a better mower.
 
Originally Posted By: bubbatime
What plug did you use? Briggs is notorious for using an emissions plug that flat out sucks on some engines. Replace odd part numbers with a Champion rc12yc.

It does sound like your ignition coil died.


It had a Champion RC12YC in it....and that one looked fine. I replaced it with an identical one after cross-referencing plugs just to be sure.

I wonder if the machine might actually give me a 20 min run with the old spark plug back in it?
 
Originally Posted By: AMC
Lots of CT people around here! As for the coil, find the correct part number and then check ebay. Ebay is usually much cheaper than a dealer of any type and even most of the online stores. Jack's small engine.com has good prices, accurate parts diagrams and is a good place alternative to a dealer.

Not sure what your budget is, but my Craftsman (Sears) and Toro (Home Depot) self propelled push mowers are over 10 years old and have never given me a problem, even with very minimal maintenance. They are basically the same exact machine, they both come with Briggs and Stratton engines and have all the features and power you could ever need in a push mower. A new one costs about $299. One machine, purchased once for $299 and lasting at least 5 (if not 10 or more) years works out to a huge savings over purchasing junk at $168 every year. In other words, Unless you really like troubleshooting and diagnosing, I would fix yours, sell it and then buy yourself a better mower.


AMC, thanks for the input. I'm not inclined to spend $300 for a mower that "could" fail within 5 yrs. Right now, I'm buying $150-$160 mowers that last 3-5 yrs typically. This one failing at the 2 yr point has not been the norm on the last 6 of these I've had. But, no doubt these are getting cheaper as there are more plastic parts on this Poulan than I've ever seen before. I don't need a self-propelled and/or mulching mower for my yard, that's just another $100 and more stuff that can break. Nothing on the simplest gas mowers should really fail within 5 yrs except the engine...that Briggs and Stratton's problem. I don't see why my B&S series 450E engine should be much different than the one on your upgraded mower with more features. I prefer a simple mechanical mower with a quality engine capable of lasting.

My last $150 mower went 5 yrs with the engine running perfectly. It was rot on the deck/wheel mounts that failed because I hadn't been properly cleaning the undercarriage. The first wheel frame rotted off after 2-1/2 yrs. Regardless, I pushed that around the yard on 3 wheels for another 2-1/2 yrs...lol. I'd have gone longer except my neighbor asked me to start doing his yard too, and 1/2 acre on 3 wheels was too much on my back. So I'm really disappointed that this one that has been religiously cleaned and serviced....gave me an engine problem so soon.

I'll give the coil a shot at $30-$38. Which is about all I'd be willing to spend on a 2 yr old mower. If I do buy another one of these (same model is still sold in 2017), I will have a fairly nice source of ready spare parts for it. I'd have no problem spending $250 for a no-frills cheaper decked-out mower, if the engine is of the quality of those "loaded" units that cost $300-$500. Basically, I'm buying the engine that sits on wheels.
 
I see that in replacing a coil one must set the flywheel/armature gap correctly (anything from 0.006 to 0.014"). Seems simple enough once I find the spec. Ideally, a shim to set the gap would come with a new coil. The B&S maintenance manual gives no specifics, and certainly no info on swapping out a coil pack, that's a "dealer" job...or go on line to find "how to."

In reading the B&S manual, I see where they state a 2 yr warranty on the B&S engine for major engine parts. I still have to August 2017 on mine. I don't see where I violated any of their conditions of use. 100% stock mower - proper OCI's with proper oil - air filter kept clean - underside kept clean - no E85 used for fuel. Don't see why I couldn't at least get a new ignition coil supplied free of charge under the 2 warranty. Those shouldn't fail that soon. It's not like this is a gummed up carb issue from using 2 yr old gas or something.

What about timing? Is there anything in HV Coil replacement that could alter the timing and require resetting with timing light, etc.? I used to adjust the timing often on old mechanical distributor cars. But this is only 1 cylinder, not 6/8 cyls. There's no easy access to a crankshaft dampener to even check timing. I'm guessing it's not an issue unless you pull the engine apart further.
 
Originally Posted By: HerrStig
Originally Posted By: dwendt44
Car plugs cannot be used in a mower engine. Can be used to test for spark though.

Change the air filter anyway, and the gas filter if it has one.
Does filling up the gas tank fix problem?
My Honda mower takes the same BP6ES plug my SAAB 900 took.


The difference is the thread length. Honda/ Chonda/ OHV OPE engines typically have 3/4" of threads while the B&S flathead has 1/2" or maybe a little less.
 
Originally Posted By: 69GTX
I see that in replacing a coil one must set the flywheel/armature gap correctly (anything from 0.006 to 0.014"). Seems simple enough once I find the spec. Ideally, a shim to set the gap would come with a new coil. The B&S maintenance manual gives no specifics, and certainly no info on swapping out a coil pack, that's a "dealer" job...or go on line to find "how to."

In reading the B&S manual, I see where they state a 2 yr warranty on the B&S engine for major engine parts. I still have to August 2017 on mine. I don't see where I violated any of their conditions of use. 100% stock mower - proper OCI's with proper oil - air filter kept clean - underside kept clean - no E85 used for fuel. Don't see why I couldn't at least get a new ignition coil supplied free of charge under the 2 warranty. Those shouldn't fail that soon. It's not like this is a gummed up carb issue from using 2 yr old gas or something.

What about timing? Is there anything in HV Coil replacement that could alter the timing and require resetting with timing light, etc.? I used to adjust the timing often on old mechanical distributor cars. But this is only 1 cylinder, not 6/8 cyls. There's no easy access to a crankshaft dampener to even check timing. I'm guessing it's not an issue unless you pull the engine apart further.


Call B&S and see what they say. I have never dealt with their customer service so that would be interesting to hear about.

As far as gapping your coil, all you have to do is center the fly wheel magnet over the middle of the coil, loosen the 2 bolts holding the coil and slide it back. Now stick a .012" (most small engines) feeler gauge in between the coil and flywheel magnets, shove the coil tightly up against the feeler gauge, hold it up against the gauge and tighten the 2 bolts holding the coil. Slide the shim out and rotate the engine by hand to make sure the flywheel magnet will not hit any part of the coil as it goes by and you are done. You don't need to do anything with timing, only the gap. I actually just did this as regular maintenance on my 18 hp Kawasaki in the John Deere. It was very easy and taking the flywheel shroud off took longer than gapping the coils.
 
Thanks AMC. I looked at a few more videos last night. Realized I didn't ground my new spark plug properly when doing the spark check on Friday. Have to do that over again this morning. Other suggestions include cleaning up the flywheel magnet surfaces and the magneto pick ups to ensure the best possible spark. One video suggested you can literally lose spark when those surfaces get too oxidized/blocked with debris. Will check that as well.

Made some other notes about checking proper coil resistance at 2.5-5.0 Kohms, electrical ground still good, etc. The hardware store up the street that I bought it from said to bring it by so their "small engine guy" can check it. Got the coil part number off Jack's Small Engine/B&S websites. $32 either place.
 
8.88 Kohms across the coil with my Fluke (spec is 2.5 - 5.0 Kohms). That's toast. If I only I had known to check that Friday. Would have saved a couple days.

No spark whatsoever on the new plug. The armature magnets are quite clean and the gap is pretty tight, grabbing the magnets on each turn. Now to see if I can get a new coil on warranty or buy it myself from Jack's/B&S.

Learned some stuff that I had no doubt forgotten from 20-35 yrs ago.

Thanks for all the help.
 
To gap the coil, just loosen the bolts that hold the coil (with the magnets facing away from the coil) and slide it back away from the flywheel and snug it's hold down screws up. Rotate the flywheel so that the magnets are facing the coil, then take a standard piece of paper and fold it 2-3 times so you have 3-4 layers and slip it between the coil and magnet- loosen the screws and it will self adjust. Remove the paper, then gently turn the flywheel to check for any interference.

edit: a standard business card works pretty well too.
 
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IT LIVES.

And don't believe everything you read on the internet. The 9K ohms for my coil is fine. Briggs and Stratton doesn't list coil specs because apparently they're good if they pass their spark tester...which only repair shops have.

Who knew Eric's suggestion of a business card was the answer? Though not on the armature. But, for the kill switch grounding tabs. After tracing the coil ground wire back a ways, and verifying continuity everywhere, the only thing left was the kill bar tab. It appeared it should either ground the coil out or not. It was gunked up with lawn debris so I cleaned all that up first. Moving the bar back and forth didn't seem to open up those 2 tabs, very much, if at all. What's to lose? I stick a piece of cardboard in between them and see if it fires up. Bingo. No sputter at all right up to running speed in a second.

Recall, that earlier in the thread I mentioned my kill bar adjustment seemed different, possibly a shorter or weaker travel. That was good intuition as the only thing I knew had changed....though it took me several days to get back to it. The machine runs regardless of where that kill bar is, fully up or full down. So next step is adjust the cable/metal tabs to give that bar full range again. The lady at one shop told me they could order a coil but no refunds if it didn't fix my problem. And the old coil would be sent back to B&S to "verfiy" if it was acceptable. I didn't like that idea. Sounded like it was set up to work against me. And on top of that she said they almost NEVER EVER see a coil failure. Maybe 1/100 or more for a coil, and almost always a Carb failure. That made me head back out and retrace the entire electrical portion yet again. Eventually, something is staring you in face.

Good thing mower repair places were basically closed today or I'd have looked like a jerk and been lighter by $35-$50 while turning my mower over to them. In the end it was a coil "failure" or grounding...nothing with fuel or air.
 
Originally Posted By: The_Eric
Awesome! Good to hear you got it all sorted out and running again.


Thanks. I need a new stop cable as the old one has either stretched out and/or the plastic 90 deg outer sheath bend near the bottom has twisted/torn a bit. Either way too much slop or movement to get the cable to pull more than 1/16"-1/8" max. Went through the B&S website parts for my engine and they don't even have an assembly dwg showing the stop cable/stop-grounding bracket...everything but that one.

I'll look into trying to shorten the cable, splice, solder, etc. Safety demands having the ability for the machine to turn off if you let go of the hand lever....not some jury-rigged bracket located at the ground connection. One video I watched had a guy pull it out with vice grips and leave those on the mower.
 
Wow, the Briggs and Stratton customer service/on line help is pretty useless. I gave them my exact engine model number (which matches to one of their choices). Put that in and you get 7 exploded diagrams for the Briggs and Stratton 450 Series E #8P 502-0064-F1....see link below. None of them show a stop cable for the kill switch. Maybe, that's considered a Poulon part or part of the general mower? Sure seems like an engine controls part to me.

Their internet response is that if I supply the "correct" engine number they can send me some diagrams. Sheesh.

I can send you the parts diagram of your equipment to help you identify the correct part number you are looking for. Please verify the model number you gave me is correct, because I´m not getting any info in our database.

Enough time wasted already. That took B&S Store 20-22 hrs to send me back that "information." I'll have better luck doing it on my own.

B&S diagrams link
 
Originally Posted By: 69GTX
Wow, the Briggs and Stratton customer service/on line help is pretty useless. I gave them my exact engine model number (which matches to one of their choices). Put that in and you get 7 exploded diagrams for the Briggs and Stratton 450 Series E #8P 502-0064-F1....see link below. None of them show a stop cable for the kill switch. Maybe, that's considered a Poulon part or part of the general mower? Sure seems like an engine controls part to me.

Their internet response is that if I supply the "correct" engine number they can send me some diagrams. Sheesh.

I can send you the parts diagram of your equipment to help you identify the correct part number you are looking for. Please verify the model number you gave me is correct, because I´m not getting any info in our database.

Enough time wasted already. That took B&S Store 20-22 hrs to send me back that "information." I'll have better luck doing it on my own.

B&S diagrams link


The stop cable is always based on what model the mower is. They all usually connect to the mechanism on the engine in the same way, but the cable is a part supplied by the mower manufacturer, not Briggs and Stratton. If it is a Poulan mower, I would look up the model number of the mower on Partstree.com and you should be able to find the cable you need.
 
Thanks Jeepman. I tried partstree.com but they didn't list my mower model. Poulan site wasn't any help either. Went to Replacementparts.com and found an engine stop cable they claimed fit my machine. Went out to pull the old cable off hoping to find a part number or at least measure it for accuracy.

While playing with the stop switch end of the cable it started to make sense how it failed. The cable was bowed upwards and not straight in line with the linkage it needed to operate. It wasted most of its motion vertically. The cable started ripping through the sheath. I suspect at some point some shrub must have caught the cable and yanked it good. The started the tearing and maybe even popped off the lower cable tie. Holding that connection tight with my hand and applying horiz force, I could operate the bail and cable properly. So that meant it was "fixable" if I could keep it in that same position. The only way this tough metal cable could get "loose" is by shearing out of the plastic or ruining the "Z" bar ends. I guess these cables can rust if you make it a habit of mowing in the rain.

So after 10 min of fiddling, 2 new 6" cable ties, and a few inches of duct tape and electrician's tape, the plastic end connection is tight enough to operate the kill switch through full range of motion. The bail lever now sits under full tension 90 deg to the mower arm rails. I suspect the root cause was a bush yanking on the cable or the lower cable tie breaking, causing cable misalignment/cover shearing.

FINIS.
 
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