Vacuum Amplifier: Testing and Inspection

Requirements:
Engine must be at normal operating temperature, 80°C (176°F)
EGR valve must operate correctly
EGR thermo-vacuum valve must operate correctly.

Fig. 29 Vacuum Amplifier Test #1:

Special tool required:
Vacuum gauge or Slack-tube tester (US 4487 or equivalent)

1. Zero the slack-tube tester and connect it or vacuum gauge to the red line between the throttle body and the vacuum amplifier with a 'T' fitting.
2. Start the engine and let it idle.
Reading should be 0.3 in. Hg.

Fig. 30 Vacuum Amplifier Test #2:

3. Zero the slack-tube tester and connect it or vacuum gauge to the blue line between the vacuum amplifier and the thermo-switch.
4. Start the engine and let it idle.
Reading should be 1.9 - 3.5 in Hg.

Fig. 31 Vacuum Amplifier Test #3:

5. Connect a hand vacuum pump to the slack-tube tester or vacuum gauge with a 'T' fitting in the hose.
6. Remove the red vacuum hose from the vacuum amplifier and connect it to the 'T' fitting between the vacuum pump and the slack-tube tester or vacuum gauge.
7. Start the engine and let it idle.
8. Pump the vacuum pump until the slack-tube tester or vacuum gauge reads 0.7 - 0.8 in. Hg.
The idle speed must drop.
9. If the idle does not drop, or if any of the other test values are not within specification, replace the vacuum amplifier and then retest.