A priming system for an engine system having a throttle valve configured to regulate a flow of air and fuel into an intake manifold of an engine is disclosed. The priming system may include a first sensor configured to generate a signal indicative of an engine speed, an auxiliary fuel line configured to direct fuel from a fuel source to a location between an outlet of the throttle valve and the intake manifold, an auxiliary fuel valve disposed in the auxiliary fuel line, and a controller in communication with the first sensor and the auxiliary fuel valve. The controller may be configured determine the engine speed based on the first signal and close the auxiliary fuel valve when the engine speed is greater than or equal to a threshold engine speed. The threshold engine speed may be less than an idle speed of the engine.