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  1. #1

    Join Date
    Sep 2012
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    Florida
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    I Don't Own a Mower :(

    Mower will not start. It has spark and gas

    This is one of those cheap push mowers with a Briggs engine (3.75 hp). I am getting spark, and I have sprayed starter fluid directly into the carb. It will not start. What else can I try? It has an over the gas tank carb. I tried starting it without the air filter assembly as well. I have not checked compression yet. I did, however, remove the spark plug and pulled the starter rope. There was a lot more resistance when it was in. I do have a compression gauge. What should compression be on this engine?

    What else could be causing it to not start?

    Thanks

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  3. #2

    Join Date
    May 2011
    Posts
    224
    Location
    Inside the Beltway in Virginia
    Mower
    Old Honda HRS-21

    Re: Mower will not start. It has spark and gas

    How did you check for spark? And was it a lot of spark?

  4. #3
    briggs's Avatar
    Join Date
    Sep 2010
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    720
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    Kingston ontario canada
    Mower
    murray,jhon deere honda,mastercraft ,MTD junk and many more

    Re: Mower will not start. It has spark and gas

    sometimes a stuck valve will case this ...check compression
    when all else fails ..Hit it with a hammer

    (I am here to help out where i can ..I will not be little u for asking a Question there is no such thing as a stupid question )

  5. #4

    Join Date
    Sep 2012
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    18
    Location
    Florida
    Mower
    I Don't Own a Mower :(

    Re: Mower will not start. It has spark and gas

    The spark was strong. I used a new spark plug. I tested it by pulling the starter rope with the plug removed (grounded). I could see the sparks.

    What should the compression be? Is there anyway to get the valve to free up, or is it junk if the compression is low?

  6. #5

    Join Date
    Sep 2012
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    18
    Location
    Florida
    Mower
    I Don't Own a Mower :(

    Re: Mower will not start. It has spark and gas

    I was looking at Murray's website and it states that low oil can cause a no start issue. The air filter was saturated with oil, so it is probably a little low. Why does a low oil situation cause a mower not to start?


    Edit:

    It looks like there is a low oil switch on some mowers.

  7. #6

    Join Date
    May 2011
    Posts
    224
    Location
    Inside the Beltway in Virginia
    Mower
    Old Honda HRS-21

    Re: Mower will not start. It has spark and gas

    A cheapo with a Briggs flat head won't have that low oil sensor. If the air filter is oily, my guess is a bad valve seal. This is a seal around the valve stem that separates the crankcase from the combustion chamber.

  8. #7

    Join Date
    Jun 2013
    Posts
    3
    Location
    Pennsylvania
    Mower
    I Don't Own a Mower :(

    Re: Mower will not start. It has spark and gas

    check flywheel key make sure its ok

  9. #8

    Join Date
    Aug 2011
    Posts
    713
    Location
    Kansas
    Mower
    Toro self propelled troybilt bronco

    Re: Mower will not start. It has spark and gas

    You should already have the low oil thing taken care of because you are supposed to check it before trying to start it. The air filter is more than likely oily because it is a oil type air filter. It is supposed to be that way in other words. It might help to read your book that comes with the mower. Then you will know how it works. That in itself will eliminate about half of your troubleshooting. Simple things can prevent those mowers from starting. Things like a dirty air filter for example. So can complicated things, like the rinky dinky plastic cam shaft gear spinning free on the metal shaft. Running them with No oil or low oil can prevent them from ever starting again. Better start from the basics. Then work into things like valves.

  10. #9
    pugaltitude's Avatar
    Join Date
    Jan 2012
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    935
    Location
    Scotland
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    Lots

    Re: Mower will not start. It has spark and gas

    You need a spark tester to check for spark. Checking with a plug only shows a spark.
    A spark tester checks the coil at full load as if under compression conditions.
    I would say carb problem. Clean carb and fit 795083 diaphragm/ gasket set.
    The "best" engine you will ever own!

    Briggs & Stratton MST.

  11. #10

    Join Date
    Sep 2012
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    Location
    Florida
    Mower
    I Don't Own a Mower :(

    Re: Mower will not start. It has spark and gas

    The engine didn't have compression. I removed the head and turned the flywheel nut manually. The valves do not open and close as they should. The odd thing is that if I turn the flywheel the wrong way (counterclockwise) the valves open and close. What do you think could be causing this problem? Camshaft?

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