Outdoor Power Equipment and Small Engines - mower runs great then quits

I have read several of these posts and gotten help a number of times. Thanks to you all. I have an Ariens mower with a 16hp B&S twin engine. It starts fine and runs for about 30 minutes, then dies. I can restart after a few minutes but the same thing occurs. The air filter is new, oil is fine, fuel filter new and I cleaned everything the manual said to clean. Can anyone offer any suggestions? Thanks, Sheila

Hello Sheila!

Do you have spark when it dies? How long do you have to wait before you can restart it?

I'm not sure what you mean by spark. It will try to start and just quit again. It will start again and run fine for a while after it seems to cool off, about 15 to 30 min. Thanks for replying.

I'm trying to determine if the spark plugs are sparking when you try to start it, immedialtely after it shuts off. It sounds like you may have a bad coil, but checking for spark at the plugs while cranking is the first step in diagnosis. You can remove the plugs and make sure they are contacting metal on the engine while connected to the plug wire, and crank the engine while watching for spark at the electrode.

I got no spark immediately after it quit, and a little spark after about five minutes. It will still start and run fine after about 30 to 45 min. I have a new coil ordered, but is there anything else it could be. It looks like a big job to put that on. Do I have to take the engine off? Thanks for all your help!

I agree with cheese. It is 100% the coil. What happens is when the mower is started cold everything is fine and dandy, but once the engine warms up, the soldered joint in the coil heats up and starts to liquify until it eventually seperates and causes an open circuit in the coil and thus the coil quits producing a spark. Then once the mower is stopped the engine temporarily rises in temperature then eventually cools down and the soldered joints join back together and the mower works again. This explanation was e-mailed to me from briggs and stratton in a reply to a question I sent them. Also, to replace the coil all you have to do is remove the shroud on top of the engine and the coil will be sitting right there next to the flywheel. Just remove the two small bolts holding it in place and unplug the grounding wire on the spade terminal on the side of the coil. Then just reverse the process to install the new coil. Also you will have to set the air gap between the flywheel and the coil. To do this just use a buisiness card or a dollar bill folded in half length ways and put it between the coil and the flywheel. Then let the magnet hold the coil against the flywheel. Then tighten the two small bolts. Then hold one end of what ever you used and rotate the flywheel and it will slide right out. Then your done. Hope this helps.:)

Thank you all! Will try this today and let you know. It is a twin so I guess we'll try the one that didn't spark first? Really appreciate the help. Sheila

There is only one coil, unless this engine is a vanguard. The coil has 2 leads coming from it, and you can replace it as described by Mower17.

It is a twin. I should have told you all that. I have replaced both coils and it is still quitting after about 30 min. It seems to do it quicker when it is hot out. It will restart after it cools off, but I have to choke it longer to get it to restart. The people where I got the coils said that was most likely the problem and had no other suggestions. I haven't checked for spark again when it quits. Should I do that? If still no spark, any other suggestions? Thanks so much, Sheila

Yes, when it quits, check to see if you have spark. If you still have spark, make sure that the gas tank vent is not clogged.

Are you sure you are losing spark? I wish I knew you had 2 coils before saying that was the problem. Very little chance that both would go bad at the same time. Most twin cylinder briggs engines have one coil with 2 leads. The vanguard twins and a few other twins have 2 seperate coils. If you are losing spark from BOTH coils, there is another problem, common to both coils...like a kill wire pinched. Look behind the starter if this is a vanguard. Sometimes the kill wire gets pinched behind it and when the engine heats up, the wire makes contact to the engine block and kills the ignition system. This does not happen on the opposed twin engines, but it does on vanguard twins and single cylinder Briggs engines.