Speed Advance Tests

NOTE: On 1980 models, ensure that basic timing signal and curb idle speed are within specifications and disconnect electrical connector from throttle position transducer prior to performing test.

Start and run engine for 2 minutes. Increase engine speed to specified test RPM and adjust timing meter so that basic timing is observed at timing indicator. If additional advance observed on timing meter is not as specified under "Electronic Spark Control, Specifications," replace spark control computer and repeat test. Specifications

Charge Temperature & Coolant Switch Test
1. On 1980 models, connect suitable ohmmeter between black wire with tracer terminal of coolant switch and ground.
2. On 1981-82 models, turn ignition Off, then connect suitable ohmmeter between center terminal of temperature switch and ground for coolant temperature switch or between center terminal and ground terminal of charge temperature switch.

For Engine Cold
1. On 1980 models, continuity should be present at terminal. If not, replace coolant switch.

NOTE: Disregard terminal of coolant switch with orange wire connected since this wire has no function in the system.

2. On 1981-82 models, continuity should be present with resistance less than 100 ohms. If not, replace switch. Charge temperature switch must be cooler than 60° F in order to perform test properly.

For Engine Hot
1. Terminal reading should show no continuity. If continuity is present, replace coolant switch.

DETONATION SENSOR TEST
1. Connect a suitable timing light to engine.
2. Set parking brake. Start engine and position throttle on second step of fast idle cam (at least 1,200 RPM).
3. Using a suitable hand operated vacuum pump, apply 16 of vacuum to Spark Control Computer transducer.

Detonation Sensor Location:

4. Using a small metal object, tap lightly on the intake manifold near the detonation sensor, see figure. At the same time, using the timing light, look for a decrease in spark advance at the timing marks. The decrease is proportional to the strength and frequency of the tapping. 11° is the maximum timing decrease.
5. Kick engine down to normal idle speed and turn ignition "Off". Remove timing light and vacuum pump.

COOLANT SENSOR TEST
1. Connect ohmmeter to terminals of coolant sensor.
2. With engine cold and ambient temperature less than 90° F., resistance should be 500-1,000 ohms.
3. With engine at normal operating temperature, resistance should be greater than 1,300 ohms.
4. If resistance is not as specified, replace sensor.