6 Notes 6.1 Choke Breaker (CB) From the FSM: "This system opens the choke valve slightly to prevent too rich a mixture just after engine starting. However, the choke valve opening is delayed by the VTV valve." 6.2 Choke Opener From the FSM: "After warming-up, this system forcibly holds the choke valve open to prevent an over rich mixture." 6.3 Deceleration Fuel Cut System From the FSM: "This system cuts off part of the fuel in the slow circuit of the carburetor to prevent overheating and afterburning in the exhaust system during deceleration." 6.4 EVAP (Fuel Evaporative Emission Control) From the FSM:
"To reduce HC emissions, evaporated fuel from fuel tank and float chamber is routed through the charcoal canister to the carburetor for combustion in the cylinders." 6.5 HAC (High Altitude Compensation) From the FSM: "As altitude increases, the air-fuel mixture becomes richer. This system insures proper air-fuel mixture by supplying additional air to the primary low and high speed circuits of the carburetor, and advances the ignition timing to improve driveability at high altitude (above 1,198 m (3,930 ft))." 6.6 HAI (Hot Air Intake) From the FSM:
"This system leads a hot air supply to the carburetor in cold weather to improve driveability and to prevent the carburetor from icing in extremely cold weather." 6.7 HIC (Hot Idle Compensator) From the FSM: "This system allows the air controlled by the HIC valve to enter the intake manifold to maintain proper air-fuel mixture during high temperatures at idle." JimC comment: Yes, it's safe to run without it. It's more of a convenience, having the idle increase to prevent overheating, and having warm air to the carb on a cold start. 6.8 PCV (Positive Crankcase Ventilation) From the FSM:
"To reduce HC emissions, crankcase blow-by gas (HC) is routed through the PCV valve to the intake manifold for combustion in the cylinders." 6.9 Other Miscellaneous Notes Trapper50Cal (post #253 of "My Desmog Thread"): if anyone has "compressed air release" or "Pop" noises emanating from under their glove box inside the cab when they start up, they are experiencing small vapor explosions in their distributor under the cap from the distributor vent not being plumbed correctly (LIKE ME). (The post also references another thread for more info.) Version 2 / 01-May-2011 Page 23 of 24