Craftsman 20930 Operator's Manual

Contents

3) If full vacuum flows through the valve whenheated, it is okay. If there is no vacuum flow orthere is vacuum flow when the coolant is cold,replace the valve.Follow this procedure to test the three-portvacuum-switching valve:1) Apply 10" Hg of vacuum with your vacuum pumpto the middle port of the valve with a vacuumgauge at each of the other two ports.2) Refer to the same color-coded valves and sametemperature specifications as for the two-port valveabove. If the vacuum switches at the specifiedtemperature, the valve is okay. If there is novacuum to the lower port above the specifiedtemperature, replace the valve.The four-port valve must be tested two times, onceat the top two ports and once at the bottom twoports as shown in the accompanying illustration(FIGURE 14).1) Apply 10" Hg of vacuum with your vacuum pumpto one of the top two ports. The valve should holdvacuum when above the specified operatingtemperature.2) If flow occurs when the valve is warm, replace it.3) For the lower two ports, vacuum must passthrough the valve only when the engine is warm;otherwise, replace the valve.15THERMAL-CONTROLLED VACUUM-SWITCHING VALVESFIGURE 14: TESTING THE FOUR-PORT PVSRESULTS:Vacuum when warm Lower valve okayNo vacuum when warm Replace PVSRESULTS:No vacuum when warm Upper valve okayVacuum when warm Replace PVS1) Apply 10" vacuum(cold engine)4) When engine iswarm (coolantabove 125°F)2) Gauge will read 10"3) Gauge willread zeroVacuum Gauge2) Apply 10" vacuumWhen engine is cold,vacuum readingshould be zero1) Warm engine(above 125°F)3) Gauge must readsource vacuum4-PORT PVS TESTUPPER VALVE FLOWLOWER VALVE FLOW