Exhaust Gas Recirculation: Testing and Inspection

Fig. 23 Connecting Vacuum Gauge:

1. Using a three-way connector tee, connect a vacuum gauge in the line between the EGR valve and the EGR vacuum modulator. Fig. 23
2. Start the engine and set at idle rpm.
3. With the coolant temperature below 135°F, check that the vacuum gauge indicates zero at 2,500 rpm.
4. Warm-up the engine until coolant temperature exceeds 145°F, and check that the vacuum gauge indicates low vacuum, (2 - 4 in.Hg) at 2,500 rpm.
5. Check that vacuum gauge indicates zero at idle speed.

Fig. 24 Testing EGR Valve:

6. Apply manifold vacuum directly to the EGR valve with the engine idling. Fig. 24
7. The engine should run rough and may die.
8. If no problems are found during this system test, disconnect vacuum gauge and reconnect the vacuum hose to the EGR valve. Otherwise, test each component in the EGR system.