Yes, you can start a riding lawn mower without a key. Quite easily, in fact.
There’s a multitude of possible reasons why you might be needing to start a riding lawn mower without a key.
Since I pick up abused (i.e. junk) machines quite frequently, I’m usually trying to turn the engine over to determine if it is seized.
Often, there’s no battery, and even if there is it’s usually drained or dead.
Equally, the key is quite frequently missing. Who knows why, but it’s not there. So we need to figure out how to start a riding lawn mower without a key.
Luckily, this is very simple to do, albeit not practical – at least not for a permanent solution.
The ignition switch (key) simply interrupts power going to the starter motor. When you turn it to the ignition detent, that provides the power to a solenoid which then feeds the starter motor. This allows your machine to (attempt) to start.
Without the key, we can’t turn the ignition switch to the ignition position.
Tools Needed (Commissions Earned)
The solution is to bypass the ignition switch altogether.
In order to accomplish this, we need to supply power to the starter solenoid. If you look at the back side of your ignition (key) switch, you’ll see several wires coming from it.
Trace those wires down to the solenoid. There should be two posts on the solenoid.
One has the positive wire coming in and the signal wire from the ignition switch. The other post has the negative wire going to ground.
In order to provide power, we simply trick the machine into thinking that it’s getting the ignition signal from the key switch.
We do this by jumping the two posts with a metal device. Conveniently, a screwdriver works well. Just remember that it will arc and damage whatever you use, so don’t use the family heirloom.
Obviously, we need power to accomplish this.
I’d recommend removing any suspect battery and using a portable jumper pack in its place. This provides known good power and eliminates a possibly bad battery from the equation.
Just connect the positive lead from the jumper pack to the positive battery cable. Then the negative lead goes to ground.
Everything I’ve read about jumping equipment says to connect the negative lead directly to the frame for a proper ground.
Don’t tell anyone, but I’ve always used the battery cable, since this goes directly to ground anyways. But, in the off chance that your machine blows up maybe don’t listen to me?
A More Permanent Solution
Once the posts have been arced, the starter motor should fire up. But really, who wants to do this every time they start the machine?
The solution is to either replace the ignition switch or to replace the key. What may come as a surprise is that John Deere uses the same key for almost all of their equipment. For a couple of bucks you can be up and running again. I have no idea if this holds true for other manufacturers.
If you have an older machine it might be a bit trickier to find a new key, so the best option in this case is to replace the whole ignition switch.
You can get OEM parts if you can find one, or just go with an aftermarket switch. All that matters is that you can make it fit in the hole and that it has the right amount of terminals coming out the back.
The terminals vary by function, so just compare it to the one you have.
Along those lines, I think it would be pretty cool to replace all of my key ignition switches with a push button (and maybe a hidden kill switch). No more losing keys.
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