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?
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?
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!
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.
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.
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.
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