18 HP Briggs No spark

Discussion in 'MTD' started by riharley, May 26, 2011.

  1. riharley

    riharley New Member

    9
    May 26, 2011
    18.5 HP Briggs NO SPARK
    I have a MTD tractor with 18.5 Briggs & Stratton Model 42A707 2238E1
    Tractor stopped starting and then sat for over a year.
    1. Found bad starter, changed it out. It now turns over
    2. Magneto had frayed wire, changed it out .
    3. Changed oil , plugs
    4. Checked all ghorund connections, cleaned them
    5. Checked solenoid, it is working OK
    6. Battery charged

    NO spark. It turns over, fuel is spurting out of top of carb (air cleaner off). Is this normal?
    I pulled left plug and laid it on head and turned over engine and saw no spark from plug.
    Any ideas what to change/check next?

    TIm
    Bristol, RI
     
  2. dangeroustoys56

    dangeroustoys56 Collector

    Jul 26, 2010
    A little fuel might come up- excessive amounts is bad - id say the carb needs a cleaning/rebuild if needed.

    On the magneto, you said there was a frayed wire? One of the spark plug wires or the magneto kill wire ( the small wire that hooks to the ign switch)?

    Id try unhooking the magneto kill wire and see if you have spark then ( you should) - it could be grounding out either before or at the ign switch ( time for a new ign switch).
     

  3. riharley

    riharley New Member

    9
    May 26, 2011
    Thanks for the help...

    The frayed wire was one of the spark plug wires to the Magneto. I changed out whole Mag with new plug wires attached. I'll try test and also make sure ground (kill wire) is making good connection.
    Bad ignition would let motor spin but interrupt spark?
     
  4. riharley

    riharley New Member

    9
    May 26, 2011
    Tried test by disconnecting black kill wire. and got no spark
    The wire was the little black wire connected to magneto, right?


    Also cleaned off magnet on flywheel. Still No spark.
    Is there a gap size for magneto to flywheel? could it be too close?

    Anything else to try?
     
  5. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    Hi,guys! Following the post,and I'm wondering if you set the armature(coil)air gap? Too large of a gap can cause no spark .
     
  6. riharley

    riharley New Member

    9
    May 26, 2011
    what should the gap be?
     
  7. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    Air gap should be .010/.012,between the flywheel,and the coil legs.Looosen the coil,and pull it away from the flywheel enough to insert a gauge(a strip of cardboard from a cereal box is .0124),then push the coil lightly against it,and tighten the screws.pull out the cardboard,and you're all set!
     
  8. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    I just realized some thing.the black wire from the coil----has it got a little eyelet?If so,it's the coil ground,and is held in place by one of the coil screws.Check the coil,near the sparkplug wire,for a small tab.That goes to the ign switch,and grounds out,to stop the engine,when the key is turned to off,and should have a push on connector.
     
  9. riharley

    riharley New Member

    9
    May 26, 2011
    set gap correctly. still no spark. Is it is possible that the new in box Magneto is bad?
     
  10. dangeroustoys56

    dangeroustoys56 Collector

    Jul 26, 2010
    Its possible the new one could be bad .

    Usually when i set a magneto gap i leave the bolts loose, put a piece of oil filter box between the magneto/flywheel , spin the flywheel till the magnet lines up and snaps the magneto in place, tighten the mag bolts down and pull the cardbord out.

    If theres no spark the motor will turn over all day and not fire up.

    By the way- how old is the motor? It doesnt have points does it? The engine code's first two numbers are the motor's manufacture date. Youd tell if it had points by an extra wire running from the mag underneath the flywheel.
     
  11. riharley

    riharley New Member

    9
    May 26, 2011
    Model 424A707-2238E-1 Code 9908265B
    Are there points? I don't see points wire.

    I will try old Magneto and see it if works.

    to be contunued.....
     
  12. riharley

    riharley New Member

    9
    May 26, 2011
    Stumped!

    Stumped. Still no spark.

    I have tried carefully setting magneto gap and swapped back the old magneto in case the new one was bad. Still no spark either way.
    NO spark with and without kill wire on magneto.

    What should I try next? Ignition switch? I'd really need to get this baby to run.

    Tim
    Bristol, RI
     
  13. Mickey

    Mickey New Member

    Aug 14, 2010
    Going WAY out on a limb here but how are the magnets in the flywheel?

    Did some looking around and saw a pic of the mag kit. The pictue showed a button headed pin that is included. Did you get that with your new mag and what is it for?
     
  14. riharley

    riharley New Member

    9
    May 26, 2011
    Magnets are in good shape. I didn't get anything else in the magento box. Sorry still stumped.

    Can I push this tractor off a cliff now?
    :mad:
     
  15. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    Replace the coil.I think the new one is possibly bad,too.As DT56 said,it happens,sometimes!
     
  16. riharley

    riharley New Member

    9
    May 26, 2011
    Would you know how to check magneto/coil with a multimeter? Just to be on the same page, the magneto and the coil are the same thing, right? ...I'm not missing a separate coil somewhere?
     
    Last edited: May 31, 2011
  17. Mickey

    Mickey New Member

    Aug 14, 2010
    I think from common usage one can define the difference between the two. The word coil usually applies to battery powered ign systems and mag or magneto applies to self powered ign i.e. it produces its own primary power.

    Using a multimeter to check the coil/mag is just a simple resistance reading. You need to know what the nom resistance reading is for both the primary and secondary windings. For sure you don't want to find dead shorts or infinite high resistance readings. With that said I don't have information on what the nom resistance is.

    Looking at an old book I have but is new enough to cover the flat twins, if your engine has the magnatron ign system the air gap with the flywheel and ign module is .006-.010. If just the old mag style ign air gap is .010-.014.
     
  18. Arkie

    Arkie New Member

    16
    Aug 6, 2014
    same problem

    Same problem as thisa guy with same model Briggs engine.

    Any ideas?
     
    Last edited: Aug 6, 2014
  19. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    By the way,guys,....make sure there's no rust/corrosion on the magneto legs,or the mount areas.
    Also,(and please don't be offended,because it does happen),make sure the coil is on correctly,in that the side with the lettering is either up,or down,as it says on it .
     
    Last edited: Aug 6, 2014
  20. jhngardner367

    jhngardner367 Moderator

    Apr 4, 2011
    You also mention that fuel sprays out of the carb. Have you checked the flywheel key ? Even a small nick can change the timing.
    Does it have an "oil-guard",in the crankcase? If so, disconnect it,and test for spark.