Throttle Positioner System

This system consists of a diaphragm-type vacuum actuator which is linked to the carburetor throttle linkage. The actuator is controlled by a vacuum switching valve and prevents complete throttle closing under certain deceleration conditions.

3A-C Engine
When coolant temperature is below 122° F, TVSV ports J and M are open. At idle speed, there is intake manifold vacuum at the TP port; diaphragm A is pushed in by return force of the throttle valve, diaphragm B is pulled by the intake manifold vacuum and the throttle valve is held at the idle speed position. At cruise speeds, the TP port is nearly at atmospheric pressure; diaphragm A is pushed out by the spring, diaphragm B is pulled out by the spring and the throttle valve is set at a medium or high speed position.

During deceleration, there is intake manifold vacuum at the TP port; diaphragm A, delayed by VTV 1, is pushed in by return force of the throttle valve, diaphragm B, delayed by VTV 2, is pulled in by intake manifold vacuum and the throttle valve opens slightly, then slowly closes to the idle position.

When coolant temperature is above 154° F, TVSV ports M and K are open and diaphragm A is pulled by intake manifold vacuum, regardless of throttle position. At idle speed, there is intake manifold vacuum at the TP port, diaphragm B is pulled by intake manifold vacuum and the throttle valve is held at the idle speed position. At cruise speeds, the TP port is nearly at atmospheric pressure, diaphragm B is pushed out by the spring and the throttle valve is set at a medium or high speed position. During deceleration, there is intake manifold vacuum at the TP port, diaphragm B, delayed by VTV 2,is pulled by intake manifold vacuum and throttle valve opens slightly, then slowly closes to the idle position.

4K-C Engine
When coolant temperature is below 104° F, the BVSV is open and the TP is set. The throttle valve is held in a position slightly more open than at idle.

When coolant temperature is above 129° F, the BVSV is closed. At idle speed, there is intake manifold vacuum at the TP port, the TP diaphragm is pulled by intake manifold vacuum, the TP is released, and the throttle valve is set in the idle speed position. At cruise speeds, the TV port is nearly at atmospheric pressure, the TP diaphragm is pushed out by the spring, the TP is set, and the throttle valve is set at a medium or high speed position. During deceleration, there is intake manifold vacuum at the TP port. The TP diaphragm, delayed by the restrictor, is pushed by intake manifold vacuum and the TV is released. The throttle valve opens slightly, then slowly closes to the idle position