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Home >> GMC >> 1991 >> Value Van 7.4 N >> Repair and Diagnosis >> External Pages >> Different car >> Section 97 (Engine Controls - System/Component Tests - 3.9L) >> Emission Systems & Sub-Systems >> Air Injection >> No Air Supply

No Air Supply

WARNING: This page is about a different car, the 1995 Dodge Ram Wagon, 1995 Dodge Ram Van, 1995 Dodge Pickup, 1995 Dodge Dakota, and 1995 Dodge Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine, and raise engine speed to 1500 RPM. Check air supply at rubber hoses. If air supply increases with RPM, air pump operation is okay. If air pump is okay, check for leakage at hoses and fittings. Repair or replace as necessary.
  2. If hoses are okay, check pressure relief valve for leakage. If air is expelled through pressure relief valve at idle, remove air injection check valves.
  3. Blow air through check valve in normal direction of air. Air should pass freely. Blow air through opposite direction. Air should not pass. Check exhaust system backpressure. See BASIC TESTING - 3.9L article in the ENGINE PERFORMANCE section. If backpressure is okay, replace relief valve.
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