Throttle By-Pass Valve

Valves are part of carburetor and have no external connections. It is preset and does not normally require adjustment. Should a malfunction exist (see SETTING IDLE SPEED ) proceed as follows:

1. If valve is not opening enough, it affects emissions but is not noticeable when driving. Condition can only be detected by testing vehicle using a non-dispersive infrared analyzer.
2. If valve is opening too far, it causes a lack of engine braking during overrun (deceleration). Test, with transmission in neutral, by opening throttle slowly until speed is 3500 RPM. Release throttle and using stop watch, note time required for speed to decrease to 1500 RPM. Time should not exceed 3.5 seconds.
3. If new valve is available replace unit. If new valve cannot be obtained, the following method of adjustment can be used in an emergency.
4. Remove screws securing valve to carburetor body and remove valve as complete assembly. Remove countersunk screws and separate by-pass valve lower body and remove diaphragm with its return spring, floating nut and adjusting screw. Take car not to lose sealing "O" ring under adjusting screw head.
5. Using punch placed inside upper body hexagon bore, drive out upper body end brass sealing disc. Retain disc for replacement when valve has been adjusted. Reassemble valve making sure that "O" ring is correctly positioned, install on carburetor.
6. Adjust screw (counterclockwise to reduce slow down time or clockwise to increase time) until engine slow down time is between 3.0-3.5 seconds.
7. One full turn on each adjusting screw is equivalent to approximately one second. Check deceleration time after each adjustment.
   CAUTION: Do not turn screws further than necessary or tensioner may become disengaged from adjusting screw.

   When adjustment completed, reseal access hole by installing cover disc.

Fig 1: By-Pass Valve

Courtesy of CHRYSLER GROUP, LLC

Fig 2: By-Pass Valve Adjustment (Rear Carburetor Only)

Courtesy of CHRYSLER GROUP, LLC