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18.05.2021 13:52:06
Remove any covering over the engine housing. If you're checking the coil in a riding mower, your engine may not have a covering, as the mower's hood will serve as the "cover." more
See full version: How to Check a Lawn Mower Coil With an Ohmmeter
Remove any covering over the engine housing. If you're checking the coil in a riding mower, your engine may not have a covering, as the mower's hood will serve as the "cover." more
Inspect the coils, which should now be visible. One terminal should extend to the spark plug housing or boot. [links]
Pull off the spark plug cover, near the top or side of your mower's engine. more
Touch your ohmmeter's negative probe to the metal extending from the second terminal to the metal of the engine, and touch the other, positive probe to the wire on the spark plug boot. You may need to move a rubber wrap away from the spark plug wire to effectively touch the probe to the wire.
After eliminating things like oil and gas being present and that the cord is connected to the spark plug, wait 10 minutes after you’ve tried starting it and then try starting it again as an initial troubleshooting.
If you have ever tried starting your lawn mower and pulled that cord over and over without any luck, it could mean many different things including a fault with fuel/oil, the induction coil, or the spark plug.
This, in turn, melts the coil’s wire insulation causing the wires to break requiring a new ignition coil.
MOST IMPORTANT: Be sure to isolate the coil from the equipment wiring harness as well as the engine's wiring harness. That's right, unhook the ignition grounding lead from the coil itself and use the spark tester. Many a technician is fooled into replacing a good coil because the coil grounding lead was shorting out against a piece of sheet metal. DO NOT attach the tester to the spark plug for this test. The engine may start. Without the grounding lead installed, you won't be able to turn it off. If the coil is properly grounded to the engine block, engine speed is at least 250 RPM and the flywheel magnets are OK, there should be spark present in the window of the tester. If not, repeat the test double checking your procedure. Still no spark? Then and only then, replace the coil.
The ignition coil is probably the easiest thing to check and therefore the first thing to check when embarking upon ignition system troubleshooting. Install the 19368 spark tester between the high-tension lead and a good engine ground. Spin the engine over (at least 250 RPM) and watch for spark in the tester window. As simple as it seems, this is a fairly comprehensive test. The tester electrode gap is .166" wide. Those wise in the way of electrons have calculated that it takes around 13,000 volts to jump this gap. We need 10,000 to jump the gap on a cold spark plug. Add it all up and we have voltage to spare. As coil temperature can aggravate minor coil imperfections that normally wouldn't be a factor, the same test can be done on a warm engine. Engine quits while running? Hook the tester up in line with the spark plug and start the engine. When the engine quits, monitor the window. If spark is present, the problem is not in your ignition coil. By the way, this test stresses the coil well beyond the demand it would see in operation. Think about it. We're asking the coil to build enough voltage to jump TWO gaps - the tester as well as the plug. If your engine starts and runs OK cold and hot, you've got a healthy ignition coil. more
The flywheel magnet must generate a sufficient magnetic field to start the chain of events in motion. A fair test is to hold the flywheel on edge with the magnet facing up. Place the blade of a 10" #3 (1/4") straight blade screwdriver against the magnet. Release the screwdriver. The magnet should have enough strength to hold the screwdriver straight out. If we pass this test, assume the magnet is OK.
Ignition coils, particularly Magnetron & trade; coils, rarely fail. If one is suspect, perform the outlined checks exactly as mentioned.
· A bright blue spark is best. A yellow/orange spark signifies weak ignition. Not true. Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap. [links]
· An armature air gap that is too wide will prevent spark. Not true. Well, sort of not true. Briggs & Stratton air gaps cannot be made too wide to prevent spark providing the coil is healthy and the engine is spun over fast enough. A wide air gap, say .030" will ever so slightly retard the ignition timing as the magnetic field takes longer to build within the coil winding.
Mower stops mid mow Your mower may have a bad coil, especially if you cannot re-start your mower while it is still hot. If you have to wait for the mower to cool to start it, you should probably replace the ignition coil. more
It should not be touching. Use a standard size business card to adjust the air gap between the coil and flywheel magnets.
Replacing Ignition Coils or Armatures An ignition armature must be set at a precise distance from the flywheel. Your engine repair manual will provide the proper gap for your engine. Common armature gap ranges are. 006 -. here
Most ignition coils should have a primary resistance falling somewhere between 0.4 and 2 ohms; however, refer to your manufacturer’s specifications for the correct reading. If a reading of zero is displayed, that signifies that the ignition coil has shorted internally in the primary windings and needs to be replaced. more