Emission Control Systems: Testing and Inspection

Servo Diaphragm
1. Connect tachometer to the engine.
2. Run engine until it reaches normal operating temperature and ensure idle speed is within specifications.
3. Shut off engine and remove air cleaner.
4. Disconnect vacuum hose between servo diaphragm and three-way solenoid valve at servo diaphragm.
5. Using suitable vacuum hose, connect inlet manifold and servo diaphragm
6. Start engine and increase engine speed to 2000 RPM with throttle.
7. Release throttle and ensure engine speed is 1000 to 1200 RPM on 626, 900 to 1100 RPM on 1982-83 B2000 except California, or 1200 to 1400 RPM on 1982-83 B2000 California or 1000 to 1200 RPM on 1984 models.
8. If engine speed is not within specifications, turn throttle opener adjusting screw in or out until specified engine speed is obtained.
9. If correct idle speed cannot be obtained through adjustment of throttle opener, replace servo diaphragm.

Air By-Pass Valve
1. Disconnect air hose between air bypass valve and hose connector at air bypass valve.
2. Ensure all other hoses and connections are in good condition.
3. Start and run at idle.
4. Place finger over air bypass valve outlet and ensure air flows out.
5. Increase engine speed and quickly release accelerator, then ensure air stops flowing for a few seconds.
6. If air stops flowing for more than three seconds or does not flow out at all, replace air bypass valve.

Engine Speed Unit
1. Connect voltmeter to engine speed unit electrical connector.
2. Increase engine speed to 2000 RPM, then slowly decrease engine speed.
3. Record engine speed at which current flows to circuit which should be 1400 to 1600 RPM.
4. Slowly increase engine speed again and record engine speed at which current does not flow to circuit
5. If difference in two recorded engine speeds is not between 50 and 250 RPM, replace engine speed unit.

Three Way Solenoid Valve
1. Disconnect vacuum hose between three-way solenoid valve and servo diaphragm at servo diaphragm.
2. Disconnect other vacuum hose at three-way solenoid valve.
3. Disconnect electrical connector of three-way solenoid valve.
4. Blow air into vacuum hoses still connected to three-way solenoid valve and ensure air flows from open port of valve.
5. Apply battery voltage to terminals of three way solenoid valve.
6. Blow air into vacuum hose still connected to three-way solenoid valve and ensure air flows from air filter of valve.
7. If test results are unsatisfactory, replace three-way solenoid valve.