Ford Full-Size Cars 1968-1988 Repair Guide

EGR Venturi Vacuum Amplifier System



The amplifiers have built-in calibrations and no external adjustments are required. If the amplifier tests reveal it is malfunctioning, replace the amplifier. All connections are located on one side of the amplifier. A vacuum connector and hose assembly is used to assure that proper connections are made at the amplifier. The amplifier is retained with a sheetmetal screw.

  1. Operate the engine until normal operating temperatures are reached.
  3. Before the vacuum amplifier is checked, inspect all other basic components of the EGR system (EGR valve, EGR/PVS valve, hoses, routing, etc.).
  5. Check vacuum amplifier connections for proper routing and installation. If necessary, refer to the typical vacuum amplifier schematic.
  7. Remove hose at EGR valve.
  9. Connect a vacuum gauge to EGR hose. The gauge must read in increments of at most 1 in. Hg (3 kPa) graduations.
  11. Remove hose at carburetor venturi (leave off).
  13. With engine at curb idle speed, vacuum gauge reading should be within 0.3 in. Hg (1 kPa) of the specified bias valve as shown in amplifier specifications for other than zero bias. Zero bias may read from 0-0.5 in. Hg. (0-16 kPa). If out of specification, replace amplifier.
  15. Depress accelerator and release after engine has reached 1500-2000 rpm. After engine has returned to idle, the vacuum must return to bias noted in step 7. If bias has changed, replace amplifier. Also, if vacuum shows a marked increase, greater than 1 in. Hg (3 kPa) during acceleration period, the amplifier should be replaced.
  17. Hook up venturi hose at carburetor with engine at curb idle rpm. If a sizeable increase in output vacuum is observed (more than 0.5 in. Hg/2 kPa above step 7), check idle speed. High idle speed could increase output vacuum due to venturi vacuum increase. See engine decal for correct idle specifications.
  19. Check amplifier reservoir and connections as follows: Disconnect external reservoir hose to amplifier and AP or plug. Depress accelerator rapidly to 1500-2000 rpm. The vacuum should increase to 4 in. Hg (13 kPa) or more. If out of specification, replace the amplifier.