Functional Test

Fig. 65 Single Port EGR System:

1. Connect tachometer following manufacturer's instructions, start engine and run until it reaches normal operating temperature.
2. Gradually increase engine speed while observing EGR valve diaphragm. The EGR valve spindle is visible between the vacuum diaphragm and the valve housing.
3. EGR valve should begin to open at approximately 2300-2900 RPM.
4. If valve fails to open, check for vacuum at the valve port. If there is no vacuum signal, check for broken or blocked vacuum hoses in the system. If no hose problems are found, check for inoperative thermovalve.
5. If the vacuum supply system is functioning, check the EGR valve itself.
6. Apply vacuum to EGR valve using suitable pump.
7. If engine begins to run rough (EGR valve opening), valve is operating properly. If not, the diaphragm in the valve has failed or the valve is stuck closed. Replace or clean the valve as necessary.