A solvent flush cleaning system for a paint supply system. The cleaning system includes an air injection system that injects air directly into the pumping chambers of the solvent pump to entrain air within the solvent. The cleaning system preferably includes a dedicated double diaphragm pump that circulates the solvent. The air injection system preferably includes a pair of injection valves that cooperate to selectively supply pressurized air to each pumping chamber. The air injection system further includes an actuation assembly that times the injection valves so that pressurized air is supplied to each pumping chamber as that chamber expands. The actuation assembly includes actuation valves that are operated by pressure within the air chambers of the pump. When pressure builds in one air chamber, it opens the corresponding actuation valve, which in turn actuates the injection valve causing pressurized air to be supplied to the opposite pumping chamber.
