Exhaust Gas Recirculation: Testing and Inspection

Fig. 72 Testing secondary EGR valve:

1. Check the vacuum hose for routing and installation.
2. Cold start and run the engine at idle speed.
3. Check to ensure that increasing engine rpm (from idle to 2,500 rpm) does not cause the secondary EGR valve to operate. If the secondary EGR valve operates, replace the thermo valve.
4. Warm up the engine until the coolant temperature exceeds 55 degrees C or 131 degrees F.
5. Check to ensure that when engine rpm is increased as described in step 3 that the secondary valve operates. If it does not operate inspect the EGR control valve or the thermo valve.
6. Disconnect the green striped hose from the thermo valve.
7. Connect a vacuum pump to the thermo valve, Fig. 72 and apply vacuum. If it is impossible to achieve a vacuum the thermo valve is good.
8. Disconnect the green striped hose from the nipple on the carburetor.
9. Connect a vacuum pump to the green striped hose.
10. While opening the sub EGR valve by pulling it by hand apply 20kPa (5.9 in. Hg) vacuum with a vacuum pump.
11. If the idling speed becomes unstable the secondary valve is operating. Replace the EGR valve.

SUB EGR VALVE

1. Check to ensure that when the sub EGR valve is pulled by hand it moves smoothly. If the valve is hard to move remove the sub EGR valve and check it for carbon deposits and sticking. If necessary clean with a solvent and apply oil sparingly. If the valve is still hard to move replace the sub EGR valve.
2. If the sub EGR valve cannot be removed with ease spray the sub EGR valve with solvent (remove the rubber boot first) to assist removal of the valve.