Primer Bulb, Not Priming, Engine wont Start

rolmJuly 27, 2008

I have a Lawnmower with a 5.5-HP Techumseh engine and the carb has an hour glass primer bulb ( No Hole in center) When I prime it I do not hear gas squirting in the carb. If I pour gas in the carb the lawnmower starts and it runs perfect. Back to the brimer bulb it looks solid no holes or craks. What should I look for .Thanks

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1saxman

Push the primer bulb slowly and hold it in for at least 1 second. Repeat four or five times. Replace it if you still don't get a start.

    Bookmark   July 28, 2008 at 8:36AM
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larryf

The primer bulb on some Tecumseh engines is acutally a small air pump. Pressing the primer pumps air into the float bowl. This small volumn of air displaces some of the fuel that is in the float bowl. The fuel travels up the venturi tube into the venturi area. On the Tecumseh, the amount of fuel delivered is marginable probably due to emission requirements.

Sometimes the bowl gasket and the o ring around the venturi tube deteriorates and the air delivered by the primer bulb leaks out - without displacing the fuel. If the fuel level in the float bowl is maintained at a level lower than specified, the air shot from the primer bulb is unable to deliver the fuel the added distance from the fuel level to the venturi. The later Tecumseh carburetors have plastic floats that do not allow the fuel level to be adjusted.

Earlier primer bulbs were on the small and marginal size. My understanding is Tecumseh redesigned the later primer bulb to deliver a larger volumn of air. Sometimes - nothing helps except a new carburetor.

    Bookmark   July 28, 2008 at 5:17PM
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