All Models Exc. Fed. Pickup
- Start engine. Warm to normal operating temperature and run at idle. Disconnect anti-backfire valve hose at air cleaner.
- Place finger over end of hose and increase engine speed to 3000 RPM. Quickly release throttle and allow engine to return to idle.
- If vacuum is felt at end of hose, anti-backfire valve is functioning properly. If no vacuum is felt, replace anti-backfire valve.