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How to Install a Primer Bulb

By Steve Paraskavo
Well maintained primer bulbs help engines start easier.
landscape machinery image by Horticulture from Fotolia.com

Gasoline-powered tools are driven by small engines that require a primer bulb. Whether it's a garden tool or a chain saw, a primer bulb helps small engines that lack carburetors start "cold" by advancing gasoline into the engine. Over time, a bulb can become weathered and rot or just wear out from use. As a result, primer bulbs may need to be replaced so the tools are available when necessary.

Make sure the engine is off. Put safety goggles on and place a funnel into a container to empty the gasoline from the engine. Place the engine containing the primer bulb on a drip pan, or onto a work area that can be easily cleaned if gasoline contacts it.

Inspect the engine and locate the primer bulb. It may be underneath the starter housing cover or connected to the fuel lines, which may be exposed along the edge of the engine. If it's under the starter housing, use a screwdriver to remove the housing screws and place the screws away from the work area so they won't be lost.

You may need an Allen wrench to remove the primer bulb from its mount. If so, remove the Allen screws and place them with the housing cover screws. Once removed, gently pull the old primer bulb from the fuel lines. Examine the fuel lines to make sure they're in proper working condition without any cracks or weathered appearance.

Inspect the new primer bulb and note the ribbed ends. Hold the new primer bulb up to the fuel lines to measure for a proper fit. If necessary, use scissors to cut the ends of excess fuel line to adjust for any difference in size. Push the new primer bulb onto the fuel lines while making sure to connect the fuel lines securely over the ribbed ends. Reposition it back onto the mount by fastening it to the engine with an Allen wrench and screws. Replace the housing cover, then tighten the screws with a screwdriver. Refill the tank with the gasoline drained at the beginning of the procedure.


Things You Will Need

  • Safety glasses
  • Screwdriver
  • Allen wrench
  • Scissors
  • Drip pan
  • Funnel


  • Do not pull on the fuel lines too much as this may disconnect the fuel lines from the engine. Gasoline can corrode the fuel lines, so replacing any rubber parts can prolong the tool's life.


  • Do not smoke while performing this task, or have any open flame near the engine. Always work with caution around flammable materials.

About the Author


Based in Nashville, TN, Steve has been writing articles since 1996. His work appeared in journals such as "Cell Transplantation," "Psychobiology" and "Neuroscience Letters." Steve received the Frederick Rhodes, M.D. Memorial Scholarship and the Novo Nordisk Scholarship. He is currently a medical student in Nashville.