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Have an older Toro push mower a neighbor dropped off the other day. He said it starts up no problem but if you shut it off after it's warm it's impossible to get started back up until it cools back down. Where do I start my diagnostics. He thought maybe ignition coil. Any help is greatly appreciated. I will post engines numbers soon as I am not home now. Do know it has a Briggs on it. Thanks in advance!

You start with checking to see if it has spark when it is hot. No spark, it probably is a coil. Second. Is it real easy to pull the starter cord when it is hot like poor compression? That would be tight valve clearance (valve expands when hot and is held open)

I have had coils fail when the engine gets hot. I have also had people use the briggs intek gas cap on quantum push mower engine. One is vented and one is not. It will not restart if the wrong gas-cap is used. Try running and pull cap and see if it restarts. Easiest way to check coil pull gastank, and blower housing. Pull black ground wire from coil. Test run mower with full tank of gas. If it runs with no problems its the coil. Just remember to shut off use a pair of insulated pliers and pull spark plug boot from plug. If its the heat cycling problem when warm cylinder expands and won't build compression its cheaper to re-engine then rebuild.

mowerguy said:

Have an older Toro push mower a neighbor dropped off the other day. He said it starts up no problem but if you shut it off after it's warm it's impossible to get started back up until it cools back down. Where do I start my diagnostics. He thought maybe ignition coil. Any help is greatly appreciated. I will post engines numbers soon as I am not home now. Do know it has a Briggs on it. Thanks in advance!

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Mower Doctor 78006 said:

Easiest way to check coil pull gastank, and blower housing. Pull black ground wire from coil. Test run mower with full tank of gas. If it runs with no problems its the coil. Just remember to shut off use a pair of insulated pliers and pull spark plug boot from plug. If its the heat cycling problem when warm cylinder expands and won't build compression its cheaper to re-engine then rebuild.

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I am not understanding this comment. Could you please explain further? I'm reading it as running the engine WITHOUT a cooling shroud for several minutes (full tank of gas)?

No. It was an explanation of testing the coil. Remove gas-tank, pull starter housing, pull black coil wire. Reinstall starter housing, re install gas-tank. Test run with black coil wire/Coil ground pulled. If it runs great. Doesn't shut off till out of fuel. Bad coil.

lzn197 said:

I am not understanding this comment. Could you please explain further? I'm reading it as running the engine WITHOUT a cooling shroud for several minutes (full tank of gas)?

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If it doesn't shut off until out of fuel, how is the coil bad?

Mower Doctor 78006 said:

No. It was an explanation of testing the coil. Remove gas-tank, pull starter housing, pull black coil wire. Reinstall starter housing, re install gas-tank. Test run with black coil wire/Coil ground pulled. If it runs great. Doesn't shut off till out of fuel. Bad coil.

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Huh? How can that prove the coil is bad?

Apparently I misunderstood the question. I understood it to be that after warming up the engine would shut off. Run the mower for 20 min till hot. Pull the gastank, blower housing. Pull black coil wire. re install all parts you removed. Restart. If it restarts ok. with black wire pulled its the coil. If it doesn't restart with black wire pulled and engine hot. Possible cylinder expansion on heat cycling.

Fish said:

If it doesn't shut off until out of fuel, how is the coil bad?

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Mower Doctor 78006 said:

Apparently I misunderstood the question. I understood it to be that after warming up the engine would shut off. Run the mower for 20 min till hot. Pull the gastank, blower housing. Pull black coil wire. re install all parts you removed. Restart. If it restarts ok. with black wire pulled its the coil. If it doesn't restart with black wire pulled and engine hot. Possible cylinder expansion on heat cycling.

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Am I missing something here? If you essentially disconnect the "electrical shut down circuit" from the mower, and it NOW starts, how can that be the coil? I would think that if it NOW starts, you have an intermittent short or grounded switch or wire condition in the shut down or engine kill electrical circuit.

I also am not understanding your comment about cylinder expansion. Can you explain that please? An exhaust valve will get much hotter that a cylinder ever will. That is why, in my comment, I said the valve clearance would be wrong and that causes many mower engines to not start when hot because the valve is held open slightly.

No, if you pull the kill wire and it starts, it means the coil is good, and the kill circuit is ground out the coil somewhere. But I doubt that any of that is his problem, let's wait and see what his engine's model numbers are.

With what little we know about the mower, I will make a guess. It is a real old one, with the carb atop the metal tank, no primer bulb, the old auto-choke style carb. He needs to go through the carb, replace the diaphragm, and correctly preset the
choke.

But that is just a guess.

Sorry will be home later this afternoon and will get numbers posted as soon as possible. To clear up any confusion. The mower has no issues starting when it is cold. I can pull it out of the garage prime it once or twice and on the first or second pull it will fire every time. Start mowing the yard and let it warm up to full operating temperature. Shut the mower off to answer phone or move stuff in the yard and it will not start. Only when the engine is warm will it not start. Wouldn't believe it has anything to do with carb but then again I don't know. Like I said. Will get numbers posted as soon as I get home today.

So this is your mower, and this started all of a sudden? Last fall? Summer? For over a year? You are working on it for someone else? You just bought it and want to resell it?

Sounds like a Quantum. Look to the easy start choke system. Take the covers off and clean around the linkage. Clean in behind the muffler. Make sure the choke vane moves freely. Make sure the metal coil that winds up and unwinds is working. You tube has some videos on it if you look for awhile.

Naw, he mentioned priming it. these threads would be much shorter if we had the luxury of model numbers...

Engine: 123K02-0114-E1 03030156
Mower model#: 20037
Serial #: 230012926

If its a hot start issue then it could be the metal surpressor cap breaking down on end of spark plug if fitted.
When you have a hot non start then pull the metal cap off and only fit the terminal to the plug.
If it starts and keeps starting then fit a normal rubber boot and terminal.

Three common problems with this mower, all which may be causing the hard hot start problem. One, this engine likes to over heat due to grass collecting around the cylinder. Two, carb mounting bolts loosen up. Three, carb jets plug easily. Overheating might be causing the coil to breakdown when sitting with no air flow. Loose bolts may be creating a lean hot starting mixture. Partially plugged main jet again may cause a lean hot mixture. If it came into the shop I would start by removing the shroud and make sure the cooling fins are clean and at the same time I would check the carb bolts. Reinstall the shroud and run the unit until hot. Shut down wait three minutes and try starting. If no start, I would check for spark, if I had spark I would go after the carb. I would remove the carb, clean and rebuild with new float needle and seat. If no spark I would replace the coil and repeat the test.

mowerguy said:

Engine: 123K02-0114-E1 03030156
Mower model#: 20037
Serial #: 230012926

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Any chance you would respond to the other questions?

The most likely scenario is that the tank is full of old crappy fuel... or fuel that was bought from last summer or fall....

I don't see it getting much more involved than that......

It may just be that simple.........

Fish said:

Any chance you would respond to the other questions?

The most likely scenario is that the tank is full of old crappy fuel... or fuel that was bought from last summer or fall....

I don't see it getting much more involved than that......

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Mower Doctor 78006 said:

It may just be that simple.........

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well.......

that stuff happens..

This not my mower but a friends. The scenario I stated was the words he told me. So it was acting up all last summer. I am just doing the basic oil change and blade sharpening for a favor. He mentioned taking a look to see if I could find the problem. I am mechanically inclined just need a direction to start as I am not a smart engine mechanic. Small engines have became a hobby of mine and what better place to come here for information. Thanks to everyone who has had input. I just can't picture it being bad gas as it runs perfect on initial start up. Just the hot restart is the problem. Thank you Rivets I will remove shroud and check fins and carb bolts and clean the carb. It won't be till this weekend as I am swamped with school and work.

Yeah, clean filters etc... can do a whole lot of good....