Ford Escort/Lynx 1981-1990 Repair Guide



Carbureted vehicles which employ the Motorcraft model 740 and 5740 carburetors utilize five basic metering systems to control engine operating conditions. These five basic metering systems are as follows:

Choke system
Idle system
Main metering system
Acceleration system
Power enrichment system

The choke system is used for cold starting. It incorporates a bimetal spring and an electric heater for faster cold weather starts and improved driveability during warm-up.

The idle system is a separate and adjustable system for the correct air/fuel mixture at both idle and low speed operation.

The main metering system provides the necessary air/fuel mixture for normal driving speeds. A main metering system is provided for both primary and secondary stages of operation.

The accelerating system is operated from the primary stage throttle linkage. The system provides fuel to the primary stage during acceleration. Fuel is provided by a diaphragm pump located on the carburetor.

The power enrichment system consists of a vacuum operated power valve and airflow regulated pullover system for the secondary carburetor barrel. The system is used in conjunction with the main metering system to provide acceptable performance during mid and heavy acceleration.

Besides the more common gasoline fueled 1.6L base and High Output (HO) engines, Ford also offered a methanol fueled 1.6L HO engine for 1984-85. With the exception of different carburetor jetting and alcohol-resistant seals, the methanol fueled vehicles utilize a comparable fuel delivery system. However, their fuel system service specifications may vary. Consult your local Ford/Mercury dealer for further information.