Here's What Your Mower's Primer Bulb Is For And How It Works

Even for those who've never used a lawn mower before, getting it started up isn't too difficult a task. Make sure it has ample gas and oil, roll it onto a flat surface, pull down the engine stop lever, and pull the cord. With that, the engine should fire up without issue, but it's possible it won't budge. This could be due to a range of issues, such as your lawn mower's pull cord being stuck for one reason or another, or a mechanical mishap preventing the engine from starting. Then again, it could be as simple as you unknowingly overlooking your mower's primer bulb, located on the carburetor.

Alongside the pull cord and stop lever, the primer bulb is an essential element to getting a lawn mower started properly. The idea is that when you press down on this small rubber cap, it will send the proper amount of fuel to the carburetor. When you press down on it, it creates suction within the mower's fuel line. This moves the fuel to where it needs to be within the carburetor. With this transfer, there's enough fuel for the mower to boot up so you can get your yardwork done. Just to be thorough, it's a good idea to press your primer bulb a few times, roughly three by some estimates, to ensure ample fuel movement. 

For mowers equipped with them, primer bulbs are pretty important. Thus, it's equally important to take care of them and to know what to do should it break and need to be replaced.

Over time, there's a chance a primer bulb could wear down. They are just small bits of rubber after all, and this material isn't guaranteed to stick around forever. It can break down naturally with use, or even crack and split due to major temperature changes throughout the year, as rubber is prone to. Fortunately, it falling to pieces doesn't mean a whole new mower is needed. You can pop out the old one and put in a new one with ease.

1. Remove the primer bulb retainer ring cover and push in the tabs on either side of the retainer ring. This will release it from the mower so it can be pulled out.

2. Pry the old bulb out. A flathead screwdriver and a needle-nose pliers should get it out without issue.

3. Take the previous intact, or completely new, retainer ring and put it around the new bulb.

4. Push the new ring and bulb combination into the primer cavity. The tabs on the ring should click into place.

5. Replace the retainer ring cover and test the bulb out.

Though there may be additional smaller steps for specific lawn mower models, this covers the basic steps to getting a primer bulb replaced. Ideally, you won't have to replace it nearly as often as you should replace your mower's blades, for instance, but it's still a good little maintenance process to know. That is, for as long as you have a mower with a primer bulb at all.

Over time, there may be more to replace on your lawn mower than the mere primer bulb. Therefore, getting an entirely new mower could be in order. Depending on the model you choose to buy, there's a chance you won't have to deal with primer bulbs anymore at all. For example, in recent years, electric push lawn mowers have become a favorite among many, despite their differences from traditional mowers. Not only do the cost differences over time between electric and gas mowers vary, but electric mowers don't have primer bulbs. Without liquid fuel, fuel lines, or a carburetor, there's simply no use for a primer bulb on these mowers.

Meanwhile, there are some gas lawn mowers on the market these days that don't have primer bulbs either. This is because they make use of a different component to get the mower in a ready-to-start state. For these mowers, odds are you have to engage the choke to get the unit going. If it's a cold start, set the choke to "On" before starting, though if it's a warm start, the choke should be set to "Run" instead. Pull the cord or push the start button, and your mower should be up and running, just as it would be if it had a primer bulb that was pressed before attempted starting.

Though they're gradually being phased out, primer bulbs are still essential to many lawn mowers today. Knowing their purpose, how they're supposed to work, and what goes into replacing them when they go bad are all key to getting the most from your mower.