Mower engine hot start issue

[toodeep 1,758]

Will it start normal hot if you idle it down before shutting it off? I have the same mower with the 25 hp motor but I can't say I ever shut it down without idling it first.

[slowindown 494]

49 minutes ago, toodeep said:

Will it start normal hot if you idle it down before shutting it off? I have the same mower with the 25 hp motor but I can't say I ever shut it down without idling it first.

As I recall, Used to I could let it idle a bit and it would restart. I don’t think it will now. But I’m not 100% sure. I don’t usually turn it off unless I’m taking a break for awhile. I’ll test that this weekend.  
 

And Wilson yes, it seems to be a bit worse this year. 

[_Wilson_™ 6,563]

over a period of a few years, i would take @Misterclean s advise, and check, and adjust the valves, it can't hurt, and the engine might very need it, that fuel pump  might be affected if the valves are out of adjustment, like i said before, i don't like this design at all, because we all know the the new clean EPA carbs combined with ethanol gas, are troublesome enough. 

[56Sierra 1,844]

It could still be the coil or another part in the ignition system.   Two reasons:  Heat sink after shutdown and reduced voltage to the ignition system while the starter is running.

[Misterclean 421]

14 hours ago, slowindown said:

As I recall, Used to I could let it idle a bit and it would restart. I don’t think it will now. But I’m not 100% sure. I don’t usually turn it off unless I’m taking a break for awhile. I’ll test that this weekend.  
 

And Wilson yes, it seems to be a bit worse this year. 

If it runs fine until you shut it off and won't hit with starting fluid it could be flooding after you turn it off. There's a small chance that the coil super heats and quits firing or the valves that were on the edge of too tight get tight during the super heating of the engine. Engines will super heat if turned off after work on a hot day. I always let mine cool down at idle for 5 or 10 minutes. I usually blow or trim during the cool down period. It boils down to this.......you need to be prepared to diagnose your problem when it happens. Mow for an hour, kill it, wait a few minutes, verify that it will not start, spray staring fluid, if it doesn't start check for spark, if it  sparks then look for wet spark plugs (checking for flooding) . If that fails then quickly remove the blower housing and spin the flywheel backwards by hand. It should bounce sharply against the compression stroke. This method is the only way to check for true compression because it approaches the compression stroke from the opposite side of the cam shaft lobe where there is no compression release function.

Edited July 14, 2021 by Misterclean

[56Sierra 1,844]

I've heard different theories on cool down engine speeds.   One says to idle the other thought is high RPM but no load.  Logic is the ratio of fuel burned to volume of cooling air favors the fuel at idle and favors the air at high RPM.

Dunno.  I will add that my late father's GT series Cub Cadet manual states to shut the engine off with the throttle wide open.  Not following this advice causes dieseling.  It's a Kohler command I believe.   I leave blow the whole thing from top to bottom before putting it back in Mom's garage so I know the cooling fins are clean.

[slowindown 494]

I mowed the shooting range and rc runway for 2 hours after work. I gave it an extended idle cool down period. I waited about a minute. It would not restart. I got one poof with a hint of black smoke. Other than that it just spun. 
 

I drove it into the garage this morning. It started normally. I pulled the shroud the fins were clean as in the pic, just a little dirt near the valve covers. I’m going to see if they have valve cover gaskets in town and if so adjust the valves after work. If not I’ll order some and do it when they arrive. 
 

The flywheel magnets are fairly rusty. The coil arms seem to be too. I guess I’ll use some emery cloth on the magnets - don’t know if that can cause a problem. 
 

I’ll do that back spin compression test you mention @Misterclean next time. I didn’t read your post until after the fact. 
 

 

[slowindown 494]

The dealer (local co-op) didn't have the gaskets (surprise).  So I ordered some and an oem fuel pump, just in case from amazon.  Should be in by the end of next week - apparently 2-day prime shipping is a thing of the past for where I live...

[_Wilson_™ 6,563]

I'm real curious as to what the issue is, as I'm sure others are as well. 

[shadetree 5,880]

1 hour ago, slowindown said:

The dealer (local co-op) didn't have the gaskets (surprise).  So I ordered some and an oem fuel pump, just in case from amazon.  Should be in by the end of next week - apparently 2-day prime shipping is a thing of the past for where I live...

amazon's servers were down last couple days, they were hacked...lol.

[Misterclean 421]

22 hours ago, slowindown said:

The dealer (local co-op) didn't have the gaskets (surprise).  So I ordered some and an oem fuel pump, just in case from amazon.  Should be in by the end of next week - apparently 2-day prime shipping is a thing of the past for where I live...

According to your diagnostics the fuel pump will not repair the problem because you said starting fluid doesn't help. I just don't want you to waste money. Please read my suggestions from a few days ago.......this procedure should narrow it down to spark, fuel or compression.

[slowindown 494]

1 hour ago, Misterclean said:

According to your diagnostics the fuel pump will not repair the problem because you said starting fluid doesn't help. I just don't want you to waste money. Please read my suggestions from a few days ago.......this procedure should narrow it down to spark, fuel or compression.

 

About that. . .

 

So yesterday when I got off work, I cleaned the flywheel magnet and put the shroud back on.  I left the plastic guard off above the flywheel screen so I would be able to spin it backwards by hand.  I started mowing and mowed a good two hours.  It was much cooler than the day before and the grass wasn't nearly as thick as this was an area I regularly mow.  At dark I let it idle at least five minutes and shut it down.  It would not restart with or without choke.  Turning the flywheel backwards by hand seemed to have a good deal of compression.  I could turn it past the compression stroke but it took most of my strength and a good leveraged position.  I then pulled the air filter off and shot a very very long blast of ether into the carb - it almost seemed to boil and I think it did boil but I kept spraying.  I put the filter back on and much to my surprise, it started.  I idled it a few seconds, revved it idled it and turned it off.  Then I cranked it again and it started.  Go figure.

 

Thanks for all of the help.  Eventually, we'll get this figured out.

 

Just a thought: Is it possible that the epa has these things so jacked up that they tend to run a little lean to begin with for emissions reasons and over time the main jet may become ever so slightly clogged so that it runs even leaner making it run hotter so that the fuel is boiling off before it can get ignited?

[56Sierra 1,844]

Do you have a timing light?  Handy tool to figure out if it's fuel or spark that's got you scratching you head.

[slowindown 494]

No.  I do not.

[Misterclean 421]

This is good news because it says there is a fuel problem. The fuel is probably boiling in the lines  and/or pump. Wrap the fuel lines with insulation and make sure the cooling fins are as clean as possible.

[slowindown 494]

3 hours ago, Misterclean said:

This is good news because it says there is a fuel problem. The fuel is probably boiling in the lines  and/or pump. Wrap the fuel lines with insulation and make sure the cooling fins are as clean as possible.

I cleaned the fins really good yesterday when the shroud was off and they weren’t very dirty at all. I can wrap the lines. I wonder why is it doing it and why it has gotten worse. 

[Misterclean 421]

2 hours ago, slowindown said:

I cleaned the fins really good yesterday when the shroud was off and they weren’t very dirty at all. I can wrap the lines. I wonder why is it doing it and why it has gotten worse. 

Fuel has different blends for different time of the year which can lower the boiling points. Another thing.......an older engine runs hotter than a new engine. The cooling fan blades may be worn after a thousand hours of use. Higher octane fuel runs much cooler than low octane. Reduce the engine speed 50 rpms. Thin oil cools better than thick oil. Just a few ideas and facts. 

[LedFTed 1,127]

On 7/15/2021 at 8:59 AM, slowindown said:

I mowed the shooting range and rc runway for 2 hours after work. I gave it an extended idle cool down period. I waited about a minute. It would not restart. I got one poof with a hint of black smoke. Other than that it just spun. 
 

I drove it into the garage this morning. It started normally. I pulled the shroud the fins were clean as in the pic, just a little dirt near the valve covers. I’m going to see if they have valve cover gaskets in town and if so adjust the valves after work. If not I’ll order some and do it when they arrive. 
 

The flywheel magnets are fairly rusty. The coil arms seem to be too. I guess I’ll use some emery cloth on the magnets - don’t know if that can cause a problem. 
 

I’ll do that back spin compression test you mention @Misterclean next time. I didn’t read your post until after the fact. 
 

 

i dont like rust on these or the coil. just my opinion.

[_Wilson_™ 6,563]

from the pic i see this mower has a fuel shut off valve, try this .... next time .... let the engine cool, then cut the fuel valve off, let the engine run out of fuel,  then turn the fuel back on and see of it will start.... it might take a couple trys AFTER you turn the fuel valve back on, also.... check your oil level, and see if it's higher on the check stick, then normal and thinned by gas, mine did this when when the float valve went south, the oil was thinned, and it was hard to start, gas was slowly getting past the float valve seat, and going right into the cyclinder, and crankcase there's only one defrence .... mine does not have a fuel pump, it's gravity flow... i added a fuel cut off valve... and rebuilt the carb myself, not a single issue from then on. 

Edited July 21, 2021 by _Wilson_™

[slowindown 494]

LedFTed I cleaned all the rust off the magnets. 
 

Wilson, I’ll give your running it dry scenario a try. 
 

My valve cover gaskets should be in tomorrow. Hopefully I’ll have a chance to check the valves this weekend. 
 

BTW, since new this machine has never had one drop of ethanol gas in it - always ethanol free in my outdoor stuff. The ethanol free gas available around here is 87 octane. 

[slowindown 494]

Well I won’t know if this is the issue for a bit yet but I just took off the rear valve cover (right if you’re looking so one cyl in on your left and one is on your right).  At tdc on the comp stroke the intake valve is .014 and the exhaust is .015-.016. Book says .004-.006 for each. The front one is going to be harder to get to. It’s a tighter working space. 
 

 

Edited July 25, 2021 by slowindown

[shadetree 5,880]

32 minutes ago, slowindown said:

Well I won’t know if this is the issue for a bit yet but I just took off the rear valve cover (right if you’re looking so one cyl in on your left and one is on your right).  At tdc on the comp stroke the intake valve is .014 and the exhaust is .015-.016. Book says .004-.006 for each. The front one is going to be harder to get to. It’s a tighter working space. 
 

 

STOP !!!!.. you are mixing the valve settings up !!. NOTICE THE METRIC AND INCH SETTINGS IN THE BOOK ^^^. you said the valves are set around .14 - .15 ^^, but the book reads .14 - .15 in MM ?, yet your also saying book calls for .004 - .006 INCHES !!..LOL. both are the same !.

[slowindown 494]

54 minutes ago, shadetree said:

STOP !!!!.. you are mixing the valve settings up !!. NOTICE THE METRIC AND INCH SETTINGS IN THE BOOK ^^^. you said the valves are set around .14 - .15 ^^, but the book reads .14 - .15 in MM ?, yet your also saying book calls for .004 - .006 INCHES !!..LOL. both are the same !.

No. I measured in inches, not mm. They were .014-.016 inches. Huge gaps, relatively speaking. 
 

They were .356 to .406 mm. 
 

just did the other side. They were off about the same 

 

putting it back together now

Edited July 25, 2021 by slowindown

[Misterclean 421]

That is loose but it won't help your starting problem.  Your problem is fuel starvation from overheating. 

[slowindown 494]

1 minute ago, Misterclean said:

That is loose but it won't help your starting problem.  Your problem is fuel starvation from overheating. 

Right. But needed to be done I reckon. The gasket didn’t break on cyl no 1, the left one so I didn’t replace that one. Hope it doesn’t leak - really tight workspace there. I wasn’t too fond of how these valves adjusted. Just a lock nut where the rocker pivots and apparently the pivot is cammed. Not what I was expecting. 
 

off to see if it runs differently...