DESCRIPTION & OPERATION
To reduce cold engine emissions and improve driveability, intake manifold is heated during cold engine operation to quicken vaporization of liquid fuel. This is accomplished by the Cold Mixture Heater (CMH) and fuel heater system.
Note. Not all models are equipped with fuel heater.
- To measure resistance of CMH, unplug wiring connector. Using an ohmmeter, measure resistance between terminals. Resistance at 68°F (20°C) should be.5-2.2 ohms.
- To measure resistance of fuel heater, unplug wiring connector. Using an ohmmeter, measure resistance between terminal and float bowl. (Scheme 89) Resistance at 68°F (20°C) should be 2-6 ohms.
Scheme 89
COLD MIXTURE RELAY
Ensure continuity is present between terminals No. 1 and 2. No continuity should be present between terminals No. 3 and 4. Apply battery voltage to terminals No. 1 and 2. Continuity should be present between terminals No. 3 and 4. (Scheme 90) See COLD MIXTURE RELAY LOCATION table for location of component.
Scheme 90
| Application | Relay Location |
|---|---|
| Corolla (Carbureted) & Corolla FX | Left Fender Apron |
| Pickup | Right Fender Apron |
| Tercel Sedan | Near Wiper Motor |
| Tercel Wagon | Right Fender Apron |
COLD MIXTURE RELAY LOCATION
SYSTEM TESTING
- Start engine. Ensure coolant temperature is below 109°F (43°C). Using a voltmeter, ensure voltage is present between positive terminal and body ground. See POSITIVE TERMINAL WIRE COLORS table for correct wire color application. Ensure voltmeter probe is inserted from rear of connector. (Scheme 91) POSITIVE TERMINAL WIRE COLORS Application Wire Colors Corolla (Carbureted) & Corolla FX White/Red Pickup (1) Tercel Sedan White/Red Tercel Wagon White/Blue (1) Wire color not available.
- Warm engine to above 131°F (55°C). Ensure no voltage is present. If no problem is found, system is okay. If system fails to operate as specified, perform following component tests.
Scheme 91
See also:
• COLD MIXTURE RELAY LOCATION