Evaporative Emissions System: Testing and Inspection
SYSTEM CHECK1. Check vacuum hose routing. If hose is improperly connected, loose, clogged or leaking, repair or replace as necessary.
2. Warm engine to operating temperature and run at idle.
3. Disconnect vacuum hose from No. 1 purge control valve and connect suitable vacuum gage to hose.
4. Increase engine speed to 2500 RPM and ensure gage reads greater than 5.9 inches Hg vacuum. If not, check water thermo valve.
5. Reconnect hose to No. 1 purge control valve.
6. Disconnect vacuum hose from centermost port on bottom of No. 3 purge control valve and plug hose.
7. Connect suitable vacuum gage to exposed port of No. 3 purge control valve and ensure there is vacuum when accelerating with engine speed above 1500 RPM on 626 and B2600 models, or 1400 RPM on B2200 models. On 626 models, if operation is not as described, check three-way solenoid valve, No. 3 purge control valve and terminal 2P of EGI control unit. On B2200 models, if operation is not as described, check purge solenoid valve, No. 3 purge control valve and terminal 1V of emission control unit. On B2600 models, if operation is not as described, check EEC solenoid valve, vacuum switch valve and terminal 1H of emission control unit.
8. Reconnect hose to No. 3 purge control valve.
9. Disconnect evaporation hose at evaporation pipe and connect suitable vacuum pump to evaporation pipe.
10. Operate vacuum pump and ensure no vacuum is held. On 626 models, if vacuum is held, check three-way check valve or evaporation pipe for blockage. On B2200 and B2600 models, if vacuum is held, check the check and cut valve or evaporation pipe for blockage.
VACUUM SWITCH
1. Turn ignition switch to On position.
2. Connect a hand vacuum pump to EEC vacuum switch.
3. Apply 9.5-10.2 inches Hg vacuum to switch and measure voltage at blue/white wire terminal of switch electrical connector.
4. Voltmeter should indicate zero voltage with vacuum applied and 12 volts when vacuum is released.
5. If voltage readings are not as specified, proceed as follows:
a. Turn ignition switch to Off position.
b. Apply 9.5-10.2 inches Hg vacuum to switch and check for continuity between blue/white and black (1987) or two green (1988) wire terminals of switch electrical connector.
c. Ohmmeter should indicate continuity when vacuum is applied and no continuity when vacuum is released.
d. Replace switch if continuity is not as described.