Exhaust Gas RECIRCULATION (EGR) System Test
NOTE:
EGR systems contain different components depending on application. See Fig 2. When testing EGR system and components, use Illustration to determine component location.
NOTE:
When performing EGR system test, it may be necessary to monitor engine RPM by using scan tester. For scan tester connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS
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- Ensure EGR vacuum modulator filter is clean and in good condition. Clean filter with compressed air (if necessary).NOTE: EGR vacuum modulator filter must be installed with coarse side facing upward, away from EGR vacuum modulator.
- Using "T" connector, install vacuum gauge in line with vacuum hose on top of EGR valve. Start engine. Ensure engine runs and idles smoothly to ensure proper seating of EGR valve.
- Install Jumper Wire (SST 09843-18020) between terminals TE1 and E1 of data link connector No. 1 located in engine compartment. See Figure.
- Operate engine at 2800 RPM with engine coolant temperature less than 131°F (55°C). No vacuum reading should be obtained. EGR pipe should not be hot.
- Warm engine to normal operating temperature so engine coolant temperature is greater than 176°F (80°C). Operate engine at 2800 RPM again. Ensure a low vacuum reading is now obtained.
- Disconnect vacuum hose from port "R" of EGR vacuum modulator. See Fig 1. Using additional hose, connect port "R" of EGR vacuum modulator directly to intake manifold. High vacuum reading should be obtained with engine at 3500 RPM.NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
- Shut engine off. Remove vacuum hose, vacuum gauge and reconnect original vacuum hoses. Remove jumper wire from data link connector No. 1.
- To test EGR valve operation, remove and plug vacuum hose located on top of EGR valve. Start engine. Using vacuum pump, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If EGR system does not operate as described, each individual component should be tested. Shut engine off.