While the actual procedure for bleeding a fuel system varies from engine manufacturer to engine manufacturer, the basics are pretty much the same. If your engine has a mechanical-lift fuel pump-this is the low-pressure pump that's attached to the engine-it will often be equipped with a small lever that lets you pump fuel without turning on the engine. To purge air from the low-pressure side of the fuel system, open fuel-line unions and bleed ports downstream of the pump, one at a time, beginning with those closest to the pump, and continue pumping until fuel, and not air, runs out. The procedure for engines equipped with electric fuel pumps is similar, but instead of working a lever, you turn the ignition key to the on position to activate the pump. On some engines, the electric pump only runs when the glow plugs are operated or when the engine is actually running, so in this case the pump may have to be temporarily hot-wired.