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hp.Take for example the old style briggs 12 hp without
overhead valves.There are usually two wires coming
from underneath the flywheel cover or cap,one is the
charging wire, which comes from the alternator and it
is located underneath the flywheel, it charges the
battery thru one of the wires coming from underneath
the flywheel cover.The other wire usually a black wire
goes to the coil as a ground wire and serves to shut
engine down when you turn key off, it also winds its
way through your safety switches.These are actually
the only two wires on a 12 hp, unless it has a fuel
shutoff solonoid underneath the bowl of the carb,
which most of todays engines have.
The latest engines are mostly overhead valve with this
fuel shutoff solonoid on the bowl,which is an added
two wires to the engine,so now their are four instead
of two.The fuel shut off solonoid will have usually a
grey and black wire going to it, the black is a ground
and the grey is a hot wire, when ignition is turned on.
I f your battery is dead and you try to jump engine off,
most likely it will run until you take jumper cables
away,because the fuel shutoff solonoid needs a good
battery to operate.I MYSELF usually by pass this
solonoid by unscrewing it from the carb and snipping
the pin off even with threads, when I FIND IT BAD.It is
a shade tree method of getting out of spending 30 to
40 bucks for a solonoid.I ALSO INSTALL A cuttoff
valve between tank and carb so I CAN CUTT FUEL
OFF FROM ENGINE WHEN NOT RUNNING.
In actuality a lot of troubleshooting can be
performed,by disconnecting the wire to the coil, or
ground wire, not spark plug wire. For instance if your
engine spins and does not fire, you can disconnect
this wire,and if it fires and cranks it tells you that you
have a bad safety switch,since ground wire winds its
way through those safety switches.
The wiring on a small engine rarely gives any
trouble,most of the time its the wiring on the frame of
the mower or what its powering.Safety switches are
usually the problem associated with not running.
TIP;Indication of a bad ignition coil would be, if you
disconnect the ground wire talked about above and
the plug will not fire with a plug you know is good, is a
good indication the coil is bad, also an engine that will
run until it gets hot and shuts itself off and the when
engine cools, cranks back up is another indication
coil is going bad.
More information on safety switches can be found in
my troubleshooting guide at http://pass
smallenginetrblshtng.com