Exhaust Gas Recirculation: Testing and Inspection
1974-761. With engine at normal operating temperature, set engine speed at 3,000-3,200 RPM.
2. Disconnect and connect EGR valve vacuum hose and observe the EGR valve diaphragm.
3. When the vacuum hose is disconnected, the EGR valve diaphragm should lower. When the hose is connected, the valve diaphragm should rise.
4. If EGR valve diaphragm operates as outlined in step 3, the valve is satisfactory. If not, check vacuum tube or hose for cracks, damage or blockage. If vacuum tube or hose is satisfactory, replace EGR valve.
1977
NOTE: The engine should be cold at the start of this test.
1. Start and run engine at 2,500 RPM.
2. The EGR valve diaphragm should be stationary. If the diaphragm is activated, check for clogged vacuum hose between EGR control valve and thermo valve.
3. Warm up the engine to normal operating temperature. The EGR valve diaphragm should be activated. If not, check for cracked or clogged vacuum hose, defective thermo valve or EGR valve.
1978-82
1. Start engine and operate at idle speed.
2. With coolant temperature below 131° F, increase engine speed to 2,500 RPM and check to ensure that secondary EGR valve is not operating. If secondary EGR valve is operating, replace thermo valve.
3. Allow coolant temperature to exceed 133° F, then increase engine speed to 2,500 RPM and check secondary EGR valve operation. If secondary EGR valve does not operate, check EGR control valve and thermal valve and replace as necessary.
4. Disconnect green stripe hose at carburetor and connect a vacuum pump to vacuum hose.
5. While operating sub EGR valve by hand, apply 5.9 inches Hg. of vacuum with vacuum pump.
6. If idle speed becomes unstable, the secondary EGR valve is operating properly. If idle speed remains unchanged, replace EGR valve.