Lawn Mower Problems (1 Viewer)

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I have a lawn mower that has not been run in over a year. I bought it new and I haven't run it but 3 or 4 times back over a year ago. Now it won't start. Well, it will start when I spray carb cleaner into the carb and it will stay running as long as I keep spraying the cleaner into the carb.

I am wondering if it is the gas I am using? The mower was completely empty and I put in gas that I had been keeping in my garage for over a year. Does gas lose its potency after being stored for a long time?


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To some extent, but it also can very well become contaminated. Water has a tendency to sneak in, even when you think that it can't. I'd recommend checking the spark plug as well. A combination of bad gas and a weak spark could result in a situation where the added flammability of the carb cleaner is needed to attain combustion. A bad connection from the magneto to the plug can have the same result, so unplug the wire and give it a light sanding or wire-brushing. Also make sure that there isn't an obstruction somewhere in the fuel delivery system, such as dirt in a carb port.
smell the gas , old gas smells bad
but morelikely water is in the gas or the jets are blocked in your case
pore a bit of the old gas in a glass jar and look at the bottom for a water layer
gas can turn over time to varnish/gum and block the jets flow
carb cleaner [spray can from a auto parts store] will de-gum the jets
but you must take the float bowl off to get to the jets
most jets [a little brass bit with a small hole for gas flow] will unscrew
so you can look/see light thru them
or you can use a wire to poke the gum out or both at once [best]
gas condisioner will help old gas and gas dryer will help with water
some will do both but fresh gas is a quick cheap fix
I cleaned off the plug and it is still doing the same thing and I have sprayed a half a bottle of cleaner in the carb. I want to try new gas but I have of course got to find a place to get rid of the old gas first.

The mower is practically brand new and the gas doesn't look irregular. The gas has been sitting in my garage and I did have the vent hole open on the container. The mower was in there too but its tank was completely empty. If new gas doesn't work, I will take the mower apart and look for trash or gunk. If that doesn't work, I will buy a new lawn mower.


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I wouldn't go so far as buying a new mower. After all, it is a new mower, by my standards, at least. Mine sat outside, unused, through 21 years in Alberta weather (ie: up to its ass in snow several months of each year), and I finally decided to try using it. It wouldn't start, so I got my buddy who is a small engine mechanic to check it out. I was expecting a full motor rebuild, but all that he had to do was change the oil and the spark plug.
I am too cheap to buy a new one without someone else looking at it first. But I certainly was thinking about it today as I was cranking my ass off in the sun.


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I used to have similar problems. Every spring the lawn screamed to be cut while the mower refused to wake up from hibernation. I started using Sta-bil gas and my equipment always starts with just a few pulls now.

Gas can 'look' just fine but that doesn't mean anything. If it's been sitting around for more than a few months, it deteriorates. I hate quoting an advertisement, but they're right and I'm too lazy to find authoritative proof. From" [Broken]web site:
Any fuel, be it gasoline, diesel, or heating fuel, is made up of many different organic compounds. These compounds are constantly changing over time and become new compounds that change the characteristics of fuel. Oxygen and other elements in the environment create new molecules that build up to form gummy residues or varnish-like films that can clog fuel lines, carburetors, and injectors.
I'd suggest changing the gas, but that doesn't really fix things. There's still gas in the carb bowl you can't get out, and the extremely small holes in carb jets could already be gummed up and plugged. Nevertheless, changing the gas would be a good first step. Also, putting a carb cleaner into the gas might help if you can get it started. That may help clean out any deposits." [Broken]adding an octane booster such as 104+.
If the engine starts, you should fill your tank with fresh gas and use a fuel injector cleaner product (such as 104+ Octane Boost). If your engine does not start, then you will need to seek a professional mechanic for cleaning and repairs.
You might also check out the other" [Broken]

I can see how that can help, it adds exactly those components to the fuel that are most likely to oxidize or evaporate over time. Fuel is made up of a variety of hydrocarbons, and it's the lightest ones that are missing in old gas because of the reaction with air or simply because they evaporate. The rest of the advice on that page is sound too. If it still doesn't start, taking apart the carb and cleaning it is the only solution but that's not easy because the jets in the carb are so tiny. You can't simply shove a pipe cleaner inside, the deposits need to be disolved away.

Moral to the story is to use Sta-bil every fall when you put away the mower. Also put it in any gas cans you may not use for the winter or other equipment that is only used seasonally.
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Gold Member
I've never heard of that stuff, so it must be a Yankee brand name. Good advice, though. There's probably something similar up here. Something else that I might suggest is: If you leave the vent hole in your jerry can open, which is a good idea in changing temperatures, try sticking a dessicant filter over it. The silica gel from a medicine bottle might work.


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Contrary to what most people think, fuel can be kept for very long periods of time. This doesn't mean that the fuel you have is still good, I just want to make a point. Around 1986 I mixed up some gas for my boat. Used it, took the tank out and left it. The vent was closed with probably a half a tank left. I junked the boat but kept the outboard motor. Around 1999 I got interested in it again and dropped the motor into a barrel with water to get it running. So off I go to find the tank and I find it half full. At this point I'm wondering what I should do with the old fuel. But, when I smelled it it seemed fine. So I decided to give it a try. The starter was no longer good on this motor so I had use the recoil rope starter. In less than 10 pulls the motor was running. This motor is a 40 horse Johnson 2 cylinder motor made in the early 60s. It has a magneto ignition and I had to pull the flywheel off to clean the points up but that is it. The fuel mix only had 2-stroke oil mixed in with NO other additives. The key to keeping fuel is to keep it cold and sealed. Keep the container in the dark and keep it cool. The fuller the container the better.
Can anyone help please,i have a power devil mower that wont start,when i take the spark plug out it is always covered in oil but i dont know how to stop this,Any idears please.


Gold Member
If your spark plug is capable of making a decent spark and it comes out wet every time you try to start it, I suggest that you pull the air filter and see if it needs to be cleaned or replaced - you may not be getting enough air to support combustion. That's the easiest first step.

Note: I'm assuming that unless the motor is a 2-stroke, the plug comes out wet with gasoline and not oil.
If gass sits long enough it can separate and becomes like lacquer. Not sure if a year would do that, but I know that sitting for a long time gass will. Also this may be stupid, but have you checked to make sure you have enough oil?
From what it sounds like, there is not enough air mixing with gas before intake. Where has it been stored when not being used? If its stored where there is a lot of moisture maybe corrosion has caused build-up that is blocking the air??

How old is the gas in the tank? Can gas expire?
My mower is running rough - it's a craftsman (briggs and stratton, 2005). I've replace the air filter, cleaned the carb and replace the spark plug. The plug gets fouled after a few minutes of operation.
Simple solution, tap the float bowl. May just be a stuck float.
I have a walk-behind self-propelled front-wheel drive MTD lawn mower that just quit "self-propelling". It still works as a push mower, however the front wheels have some drag in forward motion, and they are locked up/don't rotate in reverse motion (pulling mower backwards). The drive belt is good and has proper tension, with the lever up on the handle actuating it properly. Any ideas?
When I got home with my 1930 model A Ford tudor, the gas had solidified into a Block of Varnish about three inches thick in the bottom of fuel tank. First the Gasoline loses volatile fractions , then it loses octane and runs poorly, later it loses ignitability as flashpoint rises above heat of compression and eventually becomes a solid polymer of long hydrocarbon chains.
Your answer___ Yes it does! Solid was result of 23+ years in vented tank.

Ranger Mike

Science Advisor
Gold Member
there are 3 reasons an engine wont run1.
1. lack of fuel/air
2. lack of spark
3. lack of spark at proper time
you say the engine runs when you spray carb cleaner into the carb,,,you have a lack of fuel problem..
remove all old gasoline
disassemble the carb and clean the float bowl needle and seat..and check the small fuel filter that usually is in line. make sure you have fuel flowing thru the line to the carb,,it will run
i am trying hard to fix a mtd-yard machine riding mower 17.5hp 42"swath. it runs for awhile, different time spans, then quits. just recently saw the muffler was glowing. it has fuel and spark. new plug, new air and gas filters. i got used coil and stator and swapped them in. no improvement. could the gas cutoff solenoid be the problem? has anyone experienced this and repaired it?
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doggie treats forgets! i have failed to mention that i've been into the (nikki) carb many times trying to find some kind of dirt . cleaned all the passages w/spray cleaner, no improvement.

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