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non starting mower

Discussion in 'In the Garden' started by jfg, 13 Mar 2019.

  1. jfg

    jfg

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    Hello, i wish i'd found this forum a while ago.

    I recently bought a petrol mower with a non running briggs and stratton 500e engine.

    I've done the following,
    stripped & cleaned the carb
    checked for spark
    checked compression.

    Still it won't start. Not even with easy start.

    The only niggle i've found is with the champion rc12yc plug installed, the pull start sometimes becomes unpullable. You have to ease off the pull and the pull again. kind of like something is sticking.

    With the plug out it never jams. the plug gap doesn't close so there is no piston contact (unless there is a hole in the piston). Everytime the cylinder just floods. i suspected the coil at first but the spark is strong.

    my next step is to remove the head and check internals.

    Any ideas before i do this?
     
  2. lostinthelight

    lostinthelight

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    Take the flywheel off and check the key is not damaged ,if it is it upsets the timing
     
  3. Burnerman

    Burnerman

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    Take the plug out and pull the engine over smartly......is there a spray of fuel coming out?
    Flywheel keys shearing are common on Briggs engines, and they will often fire once but not run - a sure sign!
    If you suspect flooding, try to start with no choke, no priming and heating the plug up first.
    John :)
     
  4. jfg

    jfg

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    The key is fine and the flywheel is secured in place.

    The choke is connected to nothing, it would appear. The choke likage just goes a stud on the case beneath the flywheel.

    There is a spray of fuel spurting out when the plug is removed and i've tried heating the plug on the gas hob first too.

    I'm baffled by this.

    I have spark, compression, fuel and air!!!!
     
  5. Burnerman

    Burnerman

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    Far too much fuel present there, I'm afraid - no way will the engine start when its like that!
    First thing is to clear all of the fuel away from the combustion chamber (a blast of compressed air is great for this) and try again.
    I suspect that the carburettor is actually flooding and allowing raw fuel to leak into the engine - I guess there isn't a fuel tap so you could clamp off the fuel pipe, release the float chamber bowl, hold the float up with your finger and, when you release the clamp, see if any fuel is passing.....it shouldn't be!
    John :)
     
  6. lostinthelight

    lostinthelight

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    When you say the key is fine, haveyou physically examined it it doesnt have to be sheared to stop it starting, an indentation into it will kill it
     
  7. jfg

    jfg

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    Thanks John i'll try that on the weekend.

    The woodruff is very slightly narrower than the indent in the shaft & flywheel. There is no visible misalignment.
     
  8. lostinthelight

    lostinthelight

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  9. jfg

    jfg

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    Back in the shed this morning (it's soaking inside, new roof needed) and back on the mower. I bought a 1 grade hotter plug, 6 instead of 5 but no difference.

    I checked the carb and flow stops when the floats are up, bowl is full. All jets are clear.

    I adjusted the coil to flywheel gap to 0.012" as this is low to mid range across the series. Still nothing.

    I think it's a spark problem. even though i have spark when the plug is removed and tested on the case i just can't help but think the coil is to weak. I need my partner to help with an ohm test later and will see what that throws up.

    grass is getting long now
     
  10. lostinthelight

    lostinthelight

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  11. jfg

    jfg

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    With the multimeter set to ohms i've tested the coil.

    I get various readings such as 1215, 886, 697, 303.

    As i'm getting fuel, there is compression, i still think it's spark related.

    Only other thing to check would be valves sticking open.
     
  12. Burnerman

    Burnerman

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    The spark is really only visible in the dark, I'm afraid...high voltage and low current and all that! Give it a try.
    It is possible for the valves to be faulty, and I have seen it before - they don't stick open but the pushrod can jump off if the tappet gap is too large (only OHV engines - which I think yours will be). Easy enough to pop the front cover off for a look see.
    Just thinking - as designs do vary......when you release the dead man's handle, the flywheel brake comes on. However, it also operates an ignition cut off switch under the plastic cover so best disconnect that as a test.
    John :)
     
  13. jfg

    jfg

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    deadmans handle does engage the brake and fully releases when engaged. I've tried the start with the stopwire connected and disconnected.

    It just will not fire no matter what actions i take. which is why i'm almost certain it's spark related.
     
  14. Burnerman

    Burnerman

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    I really enjoy these challenges!
    If you are still getting a spray of fuel out of the plug ‘ole, theres no way the engine will fire up.
    If you want to try a new igniter, check out GHS Ltd for pattern parts.....unfortunately, these things are pretty reliable though.
    Keep us informed!
    John :)
     
  15. jfg

    jfg

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    Ghs don't do a pattern for mine it's original only. nightmare trying to get this part!!

    Is there a way that i can set up an external coil to power the plug to test the engine ??
     
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