Replace Primer Bulb On Lawn Mower

Article by Mark Trotta

Many gas-powered lawn mowers rely on a primer button to help start the engine. Unfortunately, being made of rubber, it's just a matter of time before they crack from age and exposure. This leads to hard starting and leaking gas.

replace primer button on lawn mower

Lawn Mower Leaks Gas

Signs of a faulty primer bulb are gasoline leaking from it, and lack of pressure when you press it. Remember that there are other causes for leaking gas, such as a bad float needle, or a worn rubber gasket inside the carburetor.

After five seasons, my Craftsman lawn mower engine started leaking gas and would not start. Upon closer examination, I found that a leaking primer button was the culprit.

Should The Primer Button Have A Hole In It?

There are two styles of primer bulbs, and you cannot interchange the two. A primer bulb with no hole is used when the bulb is part of the carburetor itself. This type actually pumps fuel into the carb, and has fuel flowing through it when the engine is running.

replace primer bulb on Craftsman lawn mower

A primer bulb with a hole pumps air to atomize a small amount of fuel to help in starting the engine. This style is mounted on the air cleaner housing and is not part of the carburetor.

primer bulb leaking gas

Many Briggs & Stratton engines, including the one on my 22" Craftsman mower, use a primer button with the hole. This design has the carb bowl venting through the primer bulb hole.

A replacement bulb is inexpensive, so why not buy a genuine Briggs & Stratton part? The Briggs 694395 Primer Bulb has many applications for lawn and garden equipment engines.

The original primer button was black, and the new one is red. There is no difference at all in performance. The part came in a plastic bag with Briggs & Stratton logo and said "Made in U.S."

replace primer button on Craftsman lawn mower

Shop: Briggs & Stratton 694395 Primer Bulb

Removal and replacement are straightforward. There is a plastic clip behind the primer bulb.

Push the two retainer tabs towards center of the bulb to disengage the clip.

Grasp the clip and pull it straight out and off the primer button.

Before putting the new bulb in, clean up the opening. Insert a new primer bulb clip over a new primer bulb with the tabs facing outward to the round area of the primer button.

Briggs 694395 Primer Bulb

For a real easy install, place the new primer bulb with the clip into a 17mm socket. Press the socket into the primer bulb housing until the clip snaps into place.

I replaced my lawn mower primer bulb in an afternoon using a few common hand tools. After installation, I gave the button three squeezes and the lawn mower started on the first pull.

lawn mower primer bulb replacement

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