Exhaust Gas Recirculation: Testing and Inspection

Fig. 49 Connecting Vacuum Gauge:

Fig. 50 Testing EGR System:

1. Using a three-way vacuum tee, connect a vacuum gauge between the EGR valve and the EGR vacuum modulator. Fig. 49
2. Start the engine and maintain at idle speed.
3. With the coolant temperature below 104°F, check that the vacuum gauge indicates zero at 3,000 rpm.
4. Warm the engine coolant temperature to 129°F and check vacuum gauge reading at 3,000 rpm. The gauge should indicate low vacuum, (2 - 4 in.Hg).
5. Disconnect the vacuum hose from port R of the vacuum modulator and connect the port directly to the intake manifold with another hose. Fig. 50
6. Check that the vacuum gauge indicates high vacuum, (15 - 20 in.Hg), at 3,000 rpm. The engine may misfire and run rough as large amounts of exhaust gases are recirculated.

Fig. 51 Testing EGR Valve:

7. Apply intake manifold vacuum directly to EGR valve with the engine idling. Fig. 51
8. The engine should run extremely rough and may stall.
9. If the system does not perform as specified, test each EGR component in COMPONENT TESTING.
10. Remove the vacuum gauge and reconnect all the vacuum hoses.