EGR Venturi Vacuum Amplifier

Idle must be set to specifications, engine must be at normal operating temperature and manifold vacuum must be adequate for this test.
1. Connect a vacuum gauge hose at EGR valve (port O). The gauge may read as high as 2 inches Hg at idle.
2. Disconnect venturi hose at carburetor and increase engine speed to 2000 RPM on all except 4-97 and 4-140 engines, 4000 RPM on 4-97 engines and 3000 on 4-140 engines.
3. Connect venturi hose. Gauge should read 4 inches Hg.
4. Return engine to idle. Gauge should return to initial reading.
5. If operation is not as described previously, replace VVA.