Any small engine repair guys here? riding lawnmower problem

[tommy p]

I have a riding lawnmower with a 13.5 hp Briggs & Stratton engine.  It starts right up and runs fine for about 10 minutes and then it starts to sputter and choke out.  If I notice it right away I can ride the throttle and put it in and out of the choke position to keep it running.  If I'm able to do this successfully for 5-10 minutes, it starts to run normally and doesn't choke out again.

I've changed the air filter and spark plug with no improvement, and the fuel filter was just replaced last year.  At the recommendation of a friend, I ran some "Mechanic in a Bottle" through it to try to degunk the carburetor.  I've bought and will be using an additive that is supposed to help with problems due to ethanol in the gas.

Anybody have any other suggestions or know what could possibly cause this type of problem?

[a.bandini]

I'm no mechanic, but have seen similar issues being caused by a gas cap that no longer vented properly resulting in a vacuum in the tank.   Might be worth cracking the cap and seeing if the symptoms go away.  

 

[hamerhead]

Rule #1 - NO ETHANOL IN SMALL ENGINES! 'Tis the kiss of death.

From the interweb:

Why is ethanol bad for small engines?

Water enters your fuel system in the air that enters the fuel tank as the gasoline is burned by the engine. ... Ethanol acts as a solvent in older engines and can dissolve old gum and varnish deposits from the gas tank and fuel lines. These deposits can then clog the very small orifices in the carburetor.May 29, 2015

Sounds like it's starving for fuel. Pulling the choke makes the mix richer allowing it to keep on keepin' on. Also, check for a pinched fuel line or plugged fuel filter.

I run Seafoam thru all my stuff at least once a year. And NO ETHANOL.

[cynic]

Google ethanol free gas stations in your area. Some stations have an etoh-free option but they charge through the nose for it. Stations that only sell etoh free typically offer more reasonable prices. John Deere says 89 octane is better as well. I use 89 oct etoh-free in all my lawn equipment and also add Sta-Bil to every can. It might be overkill but i never "winterize" and after 4-5 months of nonuse everything starts in the Spring like I used it last week.

 

[mrjamiam]

I've had similar symptoms on a Honda push mower.  Runs strong for a few minutes, then cycles for a while between bogging down and then surging accompanied by the ejection of blackish smoke.  After a while it settles down and runs normally again.  In my case the fix was a new air filter, and I mean an immediate and lasting fix.

[hamerhead]

Ethanol also dries out seals, so your sh!t leaks. I avoid it like the plague.

The only way to get ethanol-free fuel here is to buy the premium 'recreational vehicle' fuel for like 30¢ more per gallon. I run it in everything we own. It's 91 or 92 octane so the cars have a little more pep, plus they get better mileage (about 10-15% better) which offsets the higher cost.

[Thundersteel]

58 minutes ago, hamerhead said:

It's 91 or 92 octane so the cars have a little more pep

Higher octane does nothing to increase power; it simply reduces detonation by burning slower.

[hamerhead]

Does so! Especially when I make that motor sound and get spit on the inside of the windshield.

Dreamcrusher.

[Carl.B]

16 hours ago, hamerhead said:

Rule #1 - NO ETHANOL IN SMALL ENGINES! 'Tis the kiss of death.

From the interweb:

Why is ethanol bad for small engines?

Water enters your fuel system in the air that enters the fuel tank as the gasoline is burned by the engine. ... Ethanol acts as a solvent in older engines and can dissolve old gum and varnish deposits from the gas tank and fuel lines. These deposits can then clog the very small orifices in the carburetor.May 29, 2015

Sounds like it's starving for fuel. Pulling the choke makes the mix richer allowing it to keep on keepin' on. Also, check for a pinched fuel line or plugged fuel filter.

I run Seafoam thru all my stuff at least once a year. And NO ETHANOL.

Do this 

1. Drain all the fuel out. You can just pour the gas into your car without worry.

2. Check fuel lines if any feel hard or dried out replace all the lines. Fuel lines are cheap and can be found at any hardware or automotive store.

3. Add 1/2 can = 8 oz of Sea Foam to the empty gas tank,  either pull the starter chord or if it is electric start set it to choke. All you want to do is get the Sea Foam in the carburetor not actually start the engine. Let it sit over night. 

4. Next day pour the remainder of the Sea Foam into you gas tank and fill with Non-Ethanol gas. You may see some black smoke when you first start it up that's just the carbon and the build up the Sea Foam cleaned up.      

5. Double check gas lines for leaks.

6. Add 1 ounce of Sea Foam per gallon of gas in your gas can, give the gas can a quick shake before pouring the gas into your mower.

7. End of the year repeat step's 1 & 3.

 

P.S.

I have the same engine in a 12 year old Snapper riding mower and still starts on the first or second pull.  

[tommy p]

Sounds like I'm doing what I can.

On 5/31/2017 at 9:42 PM, mrjamiam said:

I've had similar symptoms on a Honda push mower.  Runs strong for a few minutes, then cycles for a while between bogging down and then surging accompanied by the ejection of blackish smoke.  After a while it settles down and runs normally again.  In my case the fix was a new air filter, and I mean an immediate and lasting fix.

Air filter and spark plug were changed.

 

 

On 5/31/2017 at 9:11 PM, cynic said:

Google ethanol free gas stations in your area. Some stations have an etoh-free option but they charge through the nose for it. Stations that only sell etoh free typically offer more reasonable prices. John Deere says 89 octane is better as well. I use 89 oct etoh-free in all my lawn equipment and also add Sta-Bil to every can. It might be overkill but i never "winterize" and after 4-5 months of nonuse everything starts in the Spring like I used it last week.

 

I went to several sites that are supposed to show you where the ethanol-free gas stations are in your area, but none work by ZIP code so that was frustrating.  I couldn't find a single ethanol-free gas station listed within 50 miles - crazy!  I live just outside Richmond and I feel like there HAS to be one somewhere around.  I posted to a local community FB group asking if anyone knew of a place with ethanol-free gas but so far no responses.  I'll use the additive I found until I can locate a gas station.

 

 

On 5/31/2017 at 8:25 PM, a.bandini said:

I'm no mechanic, but have seen similar issues being caused by a gas cap that no longer vented properly resulting in a vacuum in the tank.   Might be worth cracking the cap and seeing if the symptoms go away.  

 

Funny you should mention that.  The "check engine" light in my car used to come on every once in a while if the gas cap wasn't screwed on properly.  The rubber seal on the lawnmower's gas cap falls out every time I take the cap off so I was getting a new gas cap anyway.  It would be great if that's all it was.

Carl B, I did a similar procedure to what you suggested already.  Fuel lines and filter are new as of last year and are still flexible with no leaks.  I ran the gas almost out of the mower and added a half-bottle of "Mechanic in a Bottle" (I guess maybe similar to Sea Foam?) and stopped before the tank ran dry, let it sit overnight, and then ran the mower for about 15 minutes.  It's electric start and started right up, with a little black smoke.  I thought that was a good sign, but 5 minutes in it started sputtering and choking - no improvement.  I bought a different product that claims to be an additive for ethanol gas and added to the gas I already had in my gas can.

 

 

Thanks for the input so far.  Still open to any other suggestions!

[cynic]

You're right.  Richmond looks pretty ethanolized.

[velorush]

On 6/1/2017 at 0:28 PM, cynic said:

You're right.  Richmond looks pretty ethanolized.

Thanks, Dick Gephardt!    (was that too political?)

Another thing I've found that helps is using fuel stabilizer before putting up for the winter.  Especially helpful for the tiny carburetors in trimmers.  Won't help with this problem, but will definitely help when you go to start it up next year!

[killerteddybear]

Try this link: https://www.pure-gas.org/

And, apparently aviation fuel is ethanol free. You could look into that.

[Thundersteel]

21 hours ago, killerteddybear said:

And, apparently aviation fuel is ethanol free. You could look into that.

At our airport, 100LL is currently $5/gallon!

[killerteddybear]

3 hours ago, Thundersteel said:

At our airport, 100LL is currently $5/gallon!

Just pretend you're in Canada or Mexico...

[tbonesullivan]

Does it have a carburetor? Most small engines still go that way, and they have a bunch of issues that can occur if there is dirt or goo in the system.

It's possible that the carb is flooding, or possibly the float valve is getting stuck open. There's a lot of things that can go on.

As for ethanol goo or varnish, most fuel stabilizers like STA-BIL and Seafoam already get rid of most of that. Having goo in your system is never good, something I have found out the hard way.

[tommy p]

On 6/12/2017 at 0:59 PM, tbonesullivan said:

Does it have a carburetor? Most small engines still go that way, and they have a bunch of issues that can occur if there is dirt or goo in the system.

It's possible that the carb is flooding, or possibly the float valve is getting stuck open. There's a lot of things that can go on.

As for ethanol goo or varnish, most fuel stabilizers like STA-BIL and Seafoam already get rid of most of that. Having goo in your system is never good, something I have found out the hard way.

I've run "Mechanic in a Bottle" through it and I'm now using an additive for ethanol gas, but I still have the problem.  The mower had a good day and ran like a champ when I cut the yard 2 weeks ago but then went right back to having issues the very next time.  Last Saturday I cut one row before it sputtered out and I could never get it to stay running again.  The whole yard had to be pushed.  My last resort is to try to find that Sea Foam everyone is talking about.  If that doesn't work, it has to go in the shop.  I've had it.

[tbonesullivan]

Have you cleaned out the carburetor bowl? What can happen is that many small engines do not have the high efficiency fuel filters that cars have. In fact, many have no fuel filters at all, which means debris can get into the carburetor and cause all kinds of fun.

I have several friends who work or have worked in the motorcycle repair business. With carburetor-equipped bikes, problems running are almost always the carburetor. This is why I gladly sold my carburetor bike for one with fuel injection.