System Diagnosis - EGR

Fig. 53 Vacuum Regulator Valve (VRV). 1985 Calif. 4-137 diesel:

Fig. 54 EGR system operation chart. 1985 Calif. 4-137 diesel:

1985 4-137 CALIFORNIA DIESEL ENGINES

SYSTEM CHECK

1. Inspect vacuum hoses for breaks, kinks, blockage and proper connection, and repair as needed.
2. Connect suitable tachometer to engine following manufacturer's instructions.
3. Start engine and run at normal operating temperature.
4. Disconnect vacuum hose from TVS outlet port and connect suitable vacuum gauge to valve.
5. If gauge reading is not approximately 27 inches Hg, check for defective TVS or vacuum pump.
6. Reconnect hose to TVS, disconnect hose from VR port Z, Fig. 53, and connect vacuum gauge to valve. If vacuum is not 9.25-10.4 inches, VRV is defective.
7. Reconnect vacuum hose to VRV and observe system operation under a variety of operating conditions, checking voltage values with suitable digital voltmeter.
8. If system fails to operate as outlined in chart, Fig. 54, test and replace affected components, as needed.