LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 1982 >> Magnavan Automatic Trans, Trans Mfr CD 400/M40 >> Repair and Diagnosis (Single Page) >> Engine Mechanical >> Auxiliary Emission Control Systems >> Exhaust Gas RECIRCULATION >> Testing >> System Operation

System Operation

  1. With engine at normal operating temperature, set engine speed to fast idle (or high enough to obtain at least 5 in. Hg at EGR valve). Place gloved finger beneath EGR valve so diaphragm movement can be felt.
  2. Disconnect vacuum hose from EGR valve and watch for diaphragm movement. Diaphragm should move downward (valve closed) and an increase in engine RPM should be noticed.
  3. Reconnect vacuum hose. Diaphragm should move upward (valve open) and engine RPM should decrease.
  4. If no diaphragm movement is noticed during test, check for vacuum at hose. If vacuum is present, replace EGR valve. If no vacuum is present, check for plugged or leaking hose or carburetor port.
  5. If diaphragm moves with no change in engine RPM, check manifold EGR passages for blockage.
scientia non olet · About LEMON Manuals