Vacuum Modulated (Ported) & Negative Backpressure Types
- Turn engine off. Disconnect vacuum hose from EGR valve. Place finger underneath valve and push up to depress valve diaphragm. With diaphragm depressed, plug vacuum port on EGR valve.
- Diaphragm should take over 20 seconds to return to its seated position. If diaphragm takes less than 20 seconds to return to its seat, replace EGR valve.
- Depress diaphragm and plug vacuum port. Immediately start engine and observe diaphragm movement. Diaphragm is operating properly if diaphragm moves to seated position during cranking and initial starting.
- If diaphragm does not move during cranking or initial starting, EGR valve should be cleaned.
EGR-TVS TEST (HOT)
- Remove EGR valve vacuum hose at EGR valve and connect hose to vacuum gauge. Start engine. With transmission in Park or Neutral, open throttle partially. As throttle is opened, vacuum gauge should respond with increase in vacuum reading. If operation is satisfactory, remove gauge and reconnect hose to EGR valve. If gauge does not respond to throttle opening, proceed to step 2).
- Remove carburetor-to-TVS hose from switch and connect hose to vacuum gauge. Start engine. With transmission in Park or Neutral, open throttle partially. If vacuum gauge responds to throttle opening, switch is defective. Remove switch and replace with new part. If gauge does not respond to throttle opening, check for cracked or plugged hose.