Motor just shuts off after going an hour

Discussion in 'Lawn Mowing' started by wrestlingcoach, May 20, 2005.

  1. wrestlingcoach

    wrestlingcoach LawnSite Senior Member
    Messages: 251

    I have a briggs and stratton 3.5 hp hortizontal shaft motor connected to a pump on a pull behind sprayer.

    after using it for about hour straight , the motor just shuts down

    has gas, new spark plug, age is about 7-9 years old

    then about 30 minutes later starts back up runs for 20-40 minutes then shuts down again

    I'll drive to somewhere else then it starts back up

    What is wrong w/ the motor.
  2. Pecker

    Pecker LawnSite Bronze Member
    Messages: 1,454

    Sounds like it could be overheating??? Is the engine kept clean and the cooling fins clean?
  3. wrestlingcoach

    wrestlingcoach LawnSite Senior Member
    Messages: 251

    looks pretty clean

    so what do you do for overheated motors?
  4. GreenUtah

    GreenUtah LawnSite Senior Member
    from SLC, UT
    Messages: 866

    could be vapor locking. Does that engine have a gas cap that breathes or a tube with a filter on it? If so, they could be not functioning properly and allowing enough air into the tank for continued flow. When you stop for awhile, it slowly allows enough air to leak into the tank, making it run again for a little while then die off from lack off fuel again. I've seen this on backpack blowers and three wheel edgers, even trimmers and stick edgers. Not sure on briggs engines though, but I'd make sure I eliminate that.
  5. DEEJ

    DEEJ LawnSite Member
    Messages: 230

    Excellent point on the gas tank venting. The other classic that does this is ignition. When the engine is dead, is there GOOD spark? Often ignition components will work fine when the engine is cold, but fail when hot. Let it cool down and things are fine again for a while. The cycle just keeps repeating.

  6. wrestlingcoach

    wrestlingcoach LawnSite Senior Member
    Messages: 251

    on the "Good Spark" thing

    put new spark plug wire?

    when it shut off , I try restart it but it just doesn't seem to spark well and just doesn't want to kick over

    I'll make sure the gas tank will vent
  7. Gravely_Man

    Gravely_Man LawnSite Silver Member
    Messages: 2,075

    DEEJ nailed it on the head of what I would check. To tell if it is a venting issue run the motor untill it starts to die and open the gas cap. If it stalls out before you can open the gas cap open it and then try and restart the engine. If that doesn't help run the motor until it dies; then pull the plug and with the spark plug wire still attached to the plug try to start the motor. You should see a nice blue spark. Yellow indicates a very weak spark.



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