Engine anti-diesel control

Claim 1

An engine anti-dieseling carburetor throttle valve positioner comprising, in combination, an engine carburetor having an induction passage open to essentially atmospheric pressure at one end and adapted to be connected to an engine intake manifold at the opposite end so as to be subject to varying engine vaccum, a throttle valve rotatably mounted across the passage and movable from an essentially closed first position to a second engine idle speed position and beyond to a wide open throttle position, and return, for controlling flow through said passage, and control means to move the throttle valve to the first and second positions, the control means including first means operatively biasing the throttle valve to the first closed throttle antidiesel position, second means biasing the throttle valve towards the second position, and engine manifold vacuum sensitive means operable upon engine shutdown to initially move the throttle valve to the closed throttle first position to prevent engine dieseling and subsequently permit return movement of the throttle valve to the second open idle speed position by the second spring means to condition the engine for starting, the vacuum sensitive means including a vacuum servo having a movable diaphragm dividing the servo into first and second vacuum chambers, means connecting the first chamber to manifold vacuum at a point in the carburetor induction passage below the throttle valve, plunger means connected to the diaphragm operably engagable with the throttle valve, and flow restricting means interconnecting the first and second chambers for the slow bleed of vacuum into and out of the second chamber whereby upon engine shutdown, the immediate decay of engine manifold vacuum in the first chamber permits vacuum in the second chamber to effect movement of the throttle valve to the first closed throttle anti-diesel position, the subsequent decay of the vacuum in the second chamber through the flow restricting means permitting return movement of the throttle valve to the open throttle second position by the second spring means.