Experienced gardeners share their insights in answering this question :
If you have checked for spark at the plug end of the ignition lead and don’t have one when cranking, the ignition coil has probably failed. Checking this part will require some disassembly of the mower and then the engine.
I’m afraid these are all Chinese made coils now (cheap, cheap, cheap) and are common failures in most small engines.

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The cylindrical solenoid is a low-amperage relay that safely completes the high-amperage electrical connection between the battery and starter motor when the ignition key is turned. A bad solenoid can deny electricity to the starter motor and prevent engine startup.
Check the fuse

The fuse on most riding mowers is connected to the small red wire that connects to the starter solenoid post. Check the fuse and replace it if it`s blown. If you replace the fuse and it continues to blow, you`ll need to find the short in the wiring or component that`s causing the fuse to blow.

It is not possible to drain your lawnmower battery if the solenoid is faulty. When the solenoid is damaged or faulty, it can also cause other issues such as problems starting the engine. A faulty voltage regulator or corroded battery posts are the most common causes of battery drain in lawnmowers.
If the car cranks when you turn the key, but the engine won`t start, it could be because fuel isn`t getting to the engine. One potential reason for this could be dirty fuel injectors. Over time, the fuel injector nozzles can become clogged with rust, corrosion or debris.
Loose, Dirty or Disconnected Spark Plug in Your Lawn Mower: Check it out, clean off debris, re-connect and tighten. Dirty Air Filter: Clean or replace. Fuel Not Reaching the Engine: Tap the side of the carburetor to help the flow of gas. If this doesn`t work, you might need a new fuel filter.
A solenoid is connected to a battery so that a steady current flows through it.
If you`re in a pinch: You can still start your vehicle with a bad starter or solenoid but you should head to a mechanic as soon as possible to get the issue properly diagnosed and fixed. your car, but doing so will not fix the underlying issue (which is usually shorts in the wiring).
Put the key in the run position, set the multimeter to 20 DC voltage, ground the black lead on any metal surface close by, and place the red lead on a connector at the opposite side of the ignition cylinder. If the multimeter displays a reading far from your battery voltage, the switch is bad.
Rusting, power failure, irregular pressure, missing equipment, an incorrect amount of voltage or current, dirt stuck in the system and corrosion are some of the possible reasons why a solenoid valve may not properly close or open.
Solenoid coil failure can be caused by a number of factors. Applying an incorrect voltage to the coil will cause it to fail and may cause the coil to burn out. Electrical surges or spikes may also damage the coil. Burnt out coils cannot be repaired and will need to be replaced.
If there`s no power to the coil or if power is interrupted, the solenoid will cease functioning and remain in whatever position it was last in. Often, power interrupts to the circuitry can cause the valve to stick, and it will remain that way even after you restore power, requiring a reset.
On regular solenoid valves, it can be switched back to the operating position by energizing the solenoid, while on solenoid valves with latch-lock function it will not be so. After being energized, the valve must be manually reset by pushing the reset-knob.
Starter motors should make noise when you turn your ignition key fully to activate your car. If you turn the key and do not hear anything, there`s a chance that there`s something wrong with the vehicle`s ignition switch.
Silicone spray or powdered graphite are the most easily found lubricants, or Master Lock 2300D or 2305 lock lubricant should help the lock work more smoothly.
The starter solenoid then activates the starter motor, which spins the engine a few times to turn it on. Charging systems deliver electrical energy to power your vehicle while it`s running and sustains the battery`s charge.
Let someone turn on the ignition key or press the starter button. Observe the light — if it doesn`t turn on, the solenoid is likely failing to transfer power and might need replacement. However, if the light turns on but there`s no clicking sound or starter engagement, the issue lies with the car starter.
A typical problem with the ignition switch is when your car fails to start. This sign forces you to keep making attempts to turn the engine, draining and, therefore, killing your battery.
If a starter solenoid receives insufficient power from the battery, it will fail to start the motor, and may produce a rapid clicking sound. The lack of power can be caused by a low battery, by corroded or loose connections in the battery cable, or by a damaged positive (red) cable from the battery.
If the ignition switch fails while the engine is still on, it may cut off power to the ignition and fuel systems, which will cause the engine to stall. Depending on the exact issue, the vehicle may or may not be able to be restarted a short while later.
For the most part, an ignition switch or assembly can be a straight-forward repair where labor costs are around $75 to $150. If the key will not turn, despite best intentions, then labor prices will rise because removal usually requires the turning of the cylinder.
Car suddenly stalls while operating: One of the most common symptoms of a failed ignition relay is a car that suddenly stalls while operating. If the ignition relay shorts, burns out, or otherwise fails while the engine is operating it will cut off power to the fuel pump and ignition system.
Make Sure the Gas is On

Therefore, the first step in diagnosing ignition failure is to make sure the gas is turned on. If your furnace starts after the fuel source is turned on, you`ve solved your problem.

A dead battery is one of the most common reasons why your car won`t start. Check the battery terminals for corrosion and clean them using a wire brush or battery cleaning solution. If the battery is old or damaged, it may need to be replaced entirely.
Typical issues that you will encounter when troubleshooting the ignition system include a dead battery, faulty spark plugs, ignition coils, or distributor. Ignition troubleshooting involves a series of tests and inspections to determine the root cause of the issue and take corrective actions to fix the problem.

Discover Relevant Questions and Answers for Your Specific Issue

the most relevant questions and answers related to your specific issue

How do i add transmission oil – Ariens Lawn Tractor 46"" Riding Lawn Mower 936053"
ANSWER : Should a plug or cap on top of transaxle.

Read Full Q/A … : Mtd

Keeps shutting off. Do riding Lawn Mowers have alternators?
ANSWER : Sort of they have a stator under flywheel that charges battery. if your carb has an electric solinoid on it it need voltage to stay open but that is supplied by battery. solinoid works by key switch.switch could be bad ,solinoid could be bad ,could have fuel feed problem or spark problem need more info how long does run? does it start right back up?ect hope this helps

Read Full Q/A … : Mtd

How do I speed up my Poulan 22″ Self Propelled Hi-Wheel Mower?
ANSWER : Verbally threaten to trade it in for a riding mower.

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Mower jerks when going up an incline. – Husqvarna Riding Lawn Mower 46 Cut Kohler Yth21k46
ANSWER : Belt spilling

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I have a Crafstman Riding mower model #917.273643. That ran fine one second, I shut it off for five minutes. When I went to start it back up it wouldn’t start. Cranks fine, checked the wires, fuse, and spark plug. The plug was dirty so I cleaned it. But I am not getting any spark. I bought a new plug still no spark. I also checked the plug on another motor and I had spark so the plug wasn’t bad. Any suggestions on how to troubleshoot this or what may be wrong?
ANSWER : Sounds like your coil went bad

Read Full Q/A … : Mtd

Lawn mower cranck but wont start…
ANSWER : Since you already checked for spark and air I would drain all the fuel out of it and check that fuel for water. Over time some lawn mowers end up with contaminated fuel. You can see the water sitting on the bottom of the fuel if you let it stand for a bit in a small plastic bowl.

Be sure to empty and dry out you fuel can as well. Especially if the mower stopped running right after a refuel. Which is a good sign your gas can is contaminated too.

Read Full Q/A … : Mtd

Why the engagement belt keeps falling off – Ariens 42" 19HP Lawn Tractor
ANSWER : Your idler pulley spring broke or come unhook.

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I have trouble starting a toro walk behind mower
ANSWER : All, I thought my carb was shot, so I replaced it. Still, start but no run (and had to use starting fluid). THEN!!! I noticed the spring to the “rev limiter” (just below and towards rear of carb) was not “tight”. The stupid bracket that holds the end of that spring had been bent down ~1/16″ and that caused all this heartache. CHECK YOUR REV LIMITER!!!

Read Full Q/A … : Mtd