Gasoline Engines

Ported Vacuum & Negative Back Pressure EGR Valves
1. Check vacuum hoses for correct routing and EGR valve signal tube orifice for obstructions.
2. Connect vacuum gauge between EGR valve and carburetor and check that at least 5 inches Hg vacuum is available with engine running at normal operating temperature.
3. Depress valve diaphragm, then position finger over source tube. Release diaphragm.
4. Valve is good if diaphragm takes at least 20 seconds to move to closed position. If diaphragm closes in less than 20 seconds, replace EGR valve.
Positive Back Pressure EGR Valve
1. Check vacuum hoses for correct routing and EGR valve signal tube orifice for obstructions. On engines equipped with EGR thermal vacuum switch or solenoid, there should be no EGR valve movement below the calibration temperature. If movement occurs, check TVS or solenoid for proper operation.
2. Remove EGR valve from vehicle, then apply a constant 10 inches Hg vacuum to EGR valve signal tube and observe position of valve. Valve should be closed. If not, replace EGR valve.
3. With vacuum supply still applied, direct a low pressure stream of air into EGR valve exhaust inlet. Valve should open. If not, replace EGR valve.