Exhaust Gas Recirculation: Testing and Inspection

Fig. 36 Connecting Vacuum Gauge:

Fig. 37 Testing EGR System:

1. Using a three-way connector tee, connect a vacuum gauge in the line between the EGR valve and the vacuum modulator. Fig. 36
2. Start the engine and set at idle rpm.
3. With the coolant temperature below 104°F, check that the vacuum gauge indicates zero at 2,500 rpm.
4. Warm-up the engine until coolant temperature exceeds 151°F, and check that the vacuum gauge indicates low vacuum, (2 - 4 in.Hg).
5. Disconnect the vacuum hose from port R, Fig. 37, of the EGR vacuum modulator and connect port R directly to the intake manifold with another hose.
6. Check that the vacuum gauge indicates high vacuum at 2500 rpm, (15 - 20 in.Hg).
7. As large amounts of exhaust gas are recirculated, the engine will misfire and run rough.
8. Remove the vacuum gauge and reconnect the vacuum hoses to their proper locations.

Fig. 38 Testing EGR Valve:

9. Apply manifold vacuum directly to the EGR valve with the engine idling. Fig. 38
10. The engine should run rough and may die.
11. If no problems are found during this system test, reconnect the vacuum hose to the EGR valve. Otherwise, perform COMPONENT TESTING on each component in the EGR system.