Deceleration Valve: Testing and Inspection

NOTE: Overrun valves were deleted after engine number 8S64244.

Fig. 10 Overrun valve location and exploded view:

To isolate defective overrun valve, proceed as follows:
1. Loosen clamps which secure overrun inlet hoses to air cleaner base, and free hoses from base.
2. Block both inlet ports, then start engine.
3. Observe engine idle speed. If idle speed is correct, stop engine, and reconnect one inlet hose to air cleaner base.
4. Restart engine. If idle speed is still correct, stop engine and reconnect the remaining inlet hose to air cleaner base.
5. Restart engine. If idle speed is high, valve just reconnected is defective, and must be replaced.