Here are the top 5 reasons why your riding lawn mower won’t start after running. The causes can vary, but with some simple diagnosis, we can get your machine up and running again.
Diagnosis
We know that your riding lawn mower won’t start after running. The first question is, why did it stop running? Did you shut it off, or did it die on its own? That can tell us a lot from a diagnosis standpoint.
Tools Needed (Commissions Earned)
If you shut it off
If you shut the machine off and now it won’t start, we need to check the engine itself. More specifically, we need to ensure that it’s cooling properly and that we have adequate compression.
Compression
As an engine heats up, the components enlarge microscopically due to the heat. This can cause issues with the compression as the valves no longer seat properly.
Pop the valve cover off and check the valve clearance. Refer to the specs for your machine to ensure that compression is within spec.
Overheating
Furthermore, as most riding lawn mowers are air cooled, make sure that the engine is getting proper cooling.
The engine relies on the fins to dissipate the heat, so make sure that they’re not clogged with debris and clippings. This can drastically overheat the engine.
If it Died on Its Own
If the engine died on its own, the diagnosis is a little different, but still simple.
Fuel
First, let’s start with the obvious. Did you run out of fuel? Obviously, the machine needs fuel to run, so make sure the tank is not empty.
Furthermore, there’s a chance that if the tank ran empty, the fuel line might have gotten plugged with some debris at the bottom of the tank.
It’s not uncommon for tanks to get debris, sediment or even insects on the bottom. As the fuel runs down, there’s a greater chance for these obstructions to enter and plug the fuel line.
Prior to filling the tank back up, take the fuel line off the filter and blow some compressed air back into the tank. Try to get a visual look to see if any obstructions get blown out.
Also, if the tank ran empty, it might simply need more time to prime the fuel back to the fuel pump. The engine needs to turn over to evacuate the air in the fuel line. You can speed this process by taking the fuel line off the inlet side of the fuel pump and backfill it with fresh fuel.
Obstructed Mower Deck
If the engine died while cutting, there’s a chance that the deck has simply become obstructed with too much clippings. This can happen as the cut grass builds up on the underside of the deck.
As those clippings build up, there’s increased resistance on the machine to spin the blades through. This added workload can quickly overheat the engine as well as overpowering the engine’s rated horsepower.
Quite simply, this can cause the machine to die. That said, you should be able to restart the machine without the PTO engaged. As soon as you attempt to re-engage the PTO however, it will probably sputter and die out again as the engine cannot overcome the resistance.
Voltage Regulator
Lastly, a voltage regulator issue can cause a machine to suddenly die. A faulty voltage regulator will not allow the alternator to charge the battery. This means that the machine will be running off the battery entirely, and it will quickly consume the battery.
Once it has been consumed, the engine will die as no spark is created. Furthermore, it won’t start again as the battery is not strong enough to produce spark or even turn it over most likely.
If you’re constantly finding a dead battery, take a look and test the voltage regulator to ensure that it is functioning properly.
Recap
There you have it; the top 5 reasons why your riding lawn mower won’t start after running. In my experience, the number one reason is fuel related. Hopefully you’ve found this information helpful. If you have extra advice, please let us know in the comments below.
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