Primer bulbs

by Had Robinson

updated January 3, 2026

Primer bulbs with spring loaded check valves will often cause fuel starvation in paramotors where the fuel tank is located below the engine.  This type of check valve increases the suction on the gasoline (and the negative pressure) which causes fuel vaporization and then fuel starvation.  Our advice: get rid of the primer bulb.

Pilots should use an alternate method of priming the carburetor such as pressurizing the fuel tank via an extended vent tube.  Blow into the vent tube while holding down the primer lever on the carburetor.  If the carburetor does not have a primer lever, use a toothpick to push down the meter lever diaphragm while blowing into the fuel tank vent tube.

Why the manufacturers or pilots put primer bulbs in their paramotor fuel systems is mystery that makes no sense because of the problems they cause.  The only primer bulb setup that does not cause fuel starvation is when the primer bulb is not inline but sucks and then pumps fuel directly into the air cleaner or acts as a auxiliary pump that is directly connected to the pump diaphragm chamber.