F 250 2WD Pickup V8-351 5.8L (1982)
Thermal Vacuum Valve - EVAP: Testing and Inspection
Fig. 22 Ported vacuum switches & vacuum control valves
Fig. 23 Electrical vacuum switch
VACUUM SWITCH TEST
1. With engine cold, turn ignition key to ``ON,'' connect vacuum gauge to port A, Figs. 22 and 23, and a vacuum source to port B and then C. There
should be no vacuum flow from A to B but there should be vacuum from A to C.
2. Start engine and run until it reaches normal operating temperature, then apply vacuum to port B and then port C. There should be vacuum from A
to B but no vacuum from A to C. On 4-port valve, check A1 to B1 and A2 to B2 separately.
3. If vacuum flow is not as described, replace valve.
