Cold Enrichment and Fast Idle

This system provides a rich fuel/air mixture necessary for cold start and drive operation. The flow of fuel and the positioning of both the venturi valve and the fast idle cam are regulated by the choke cap and choke control diaphragm.

Cold Enrichment CVR and Fast Idle System:

Enrichment fuel flow is metered by the tapered cold enrichment rod suspended from the upper body through a jet located in the bottom of the fuel bowl.

The cold enrichment rod height is regulated by the choke bimetal and the choke control diaphragm. Fuel is channeled through an internal passage to discharge nozzles at the venturi. The control vacuum regulator (CVR) is also regulated by the bimetal coil and the choke diaphragm. When seated or partially lifted, the control vacuum regulator restricts part of the normal control vacuum to the venturi valve operating diaphragm. This restriction allows some manifold vacuum to be applied to the diaphragm causing the venturi opening to be slightly larger than normal to prevent engine loading at idle due to an over rich fuel mixture.

Cold Enrichment CVR and Fast Idle System:

When the engine warms up and the choke bimetal coil unwraps, the CVR rises, opens the restricted port in the control vacuum circuit and allows the control of the venturi valve to return to normal as described under main metering system. As the CVR rises, the cold enrichment rod (CER) is lowered until it is seated in its jet, shutting off the cold enrichment fuel.

The cold enrichment rod has adjustable -18~C (O~F) and 24~C (75~F) cold operation positions for improved cold driveability over a wide range of temperatures.