DESCRIPTION & OPERATION
The main air jet control system helps in maintaining an optimum air/fuel ratio. This system controls airflow into the main jets of carburetor throats. When the vehicle is started, or running in power mode, control unit energizes main air jet solenoid valve in air cleaner to close extra air passage, thereby increasing fuel flow.
Auto. Trans.
- Raise and support front of vehicle. Set parking brake and block rear wheels. Insert voltmeter or test light positive probe into Yellow/Black wire terminal at control unit connector.
- Connect negative probe to ground. Start engine and place vehicle gear selector in "2" position and accelerate slowly. Battery voltage should be as indicated in SPEED SENSOR VOLTAGE CHECK table. SPEED SENSOR VOLTAGE CHECK Speed Voltage Below 11 MPH Yes Above 16 MPH No
- If voltmeter readings do not correspond to above MPH ranges, install new speed sensor and retest. If there was no voltage during step 2), check for bad electrical connection, fuse or faulty speed sensor. Repair or replace as necessary and retest.
INTAKE AIR TEMPERATURE SENSOR
Unplug air intake temperature sensor connector. Check for continuity between sensor terminals when air temperature is below 40°F (4.5°C). Check for lack of continuity when air temperature is above 73°F (23°C). Replace sensor if not within specification.
VACUUM SWITCH A
- Disconnect vacuum hose No. 2 to control box at vacuum hose manifold. Connect hand vacuum pump to hose. Check for continuity between Black/Yellow and Brown/White terminals of control box connector.
- Apply over 4 in. Hg. Continuity should not be present. If continuity is present, replace vacuum switch A. When vacuum is released, continuity should be present. If there is no continuity, replace vacuum switch A.
CONTROL UNIT CONNECTOR
Check for voltage at control unit connector (Black/Yellow wire) with ignition on. Voltage should be present. If there is no voltage, check wiring. Check Brown/Black wire for continuity between control unit and ground. Continuity should be present.
SYSTEM TESTING
- Run engine until normal operating temperature is reached. Remove air cleaner cover and filter element. Disconnect hose from main air jet solenoid valve and install vacuum pump. Start engine and apply vacuum at idle. If no vacuum is present, proceed to step 4).
- If vacuum is present, check for voltage at main air jet solenoid valve. If voltage is not present, replace solenoid valve and retest. If there is voltage, continue with test steps.
- Check speed sensor (auto. trans. only), intake air temperature sensor and vacuum switch A. Check for voltage at control unit connector (Black/Yellow wire) with ignition on. Voltage should be present. If voltage is not present, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
- Disconnect vacuum hose No. 2 from control box No. 1. Apply vacuum with engine at idle. If vacuum remains constant, disconnect vacuum gauge and reconnect air hoses and air cleaner. If vacuum is not present, check for voltage at main air jet solenoid valve.
- If voltage is not present, replace solenoid valve and retest. If there is no voltage, check the following: speed sensor (auto. trans. only), intake air temperature sensor and vacuum switch A. Check for voltage at control unit connector (Black/Yellow wire) with ignition on.
- Voltage should be present. If there is no voltage, check wiring. Ensure Brown/Black wire between control unit and ground has continuity.
