Jeep Engines - Oljeep

31 2 MOPAR PERFORMANCE PARTSINDUCTION SYSTEMVehicles with the 4.2L (258 CID) six cylinder engine wereoriginally equipped with a model BBD two venturi,feedback-type carburetor (stock).The stepper motor included with this carburetor has twotapered metering pins. Each metering pin is moved in and outof the carburetor air cavity to achieve the proper aidfuel ratio.Induction Systemdiaphragm, which is held in its extended position by fuelpressure. Fuel flow from the pump remains halted untilexcess pressure is released through the fuel return tube oruntil the carburetor float needle moves off its seat. Thisprocedure continues as long as the engine is running.Mechanical fuel pumps cannot be overhauled. Replace anymlschanical fuel pump that fails either a pressure, capacity(volume) or vacuum test.Chrome Fuel Pump Block-Off PlateThis good looking chrome plate covers the hole left whenreimoving the mechanical fuel pump for replacement withan electric pump. Gasket included.P4.529404 Chrome fuel pump block-off plate.Fuel PumpEXHAUSTMANIFOLD /OXYGENSENSOR4.2L Intake and Exhaust Manifolds60116AThe 4.2L engine uses a single action, mechanical fuelpump. The fuel pump is comprised of an actuating lever, adiaphragm and spring, an inlet valve, and an outlet valve.An eccentric lobe on the engine camshaft operates the fuelpump lever, which is linked to the pump diaphragm. Thelever pulls the diaphragm to its extended position to pumpfuel into the inlet valve. When the carburetor float needlevalve closes, fuel pump output is limited to the amount thatreturns to the fuel tank through the fuel return tube. Thefuel accumulated in the fuel pump chamber prevents thediaphragm from relaxing. The actuating lever continues tomove up and down, but it is prevented from operating theComputerized Emission Control (CEC) FuelFeedback SystemThe CEC Fuel Feedback System on 4.2L six cylinderengines controls undesirable emission in to the atmosphereand maintains the ideal aidfuel ratio to provide an optimumbalance between emission control and engine performance.This is accomplished by use of a Micro-Computer Unit(MCU), several MCU input components and several MCUoutput components.The MCU monitors various engine operating conditions.Based on these conditions, the MCU may, depending on themode of operation, generate output signals to provide theproper aidfuel mixture, proper ignition timing and engineidle speed. Each system operates in two modes ofoperation: CLOSED LOOP and OPEN LOOP.Closed loop operation occurs when the aidfuel ratio isvaried according to the oxygen content in the exhaust gas.During open loop operation, the aidfuel ratio ispredetermined by the MCU for several engine operatingconditions, such as:Start-upCold engine operationWide open throttle (W.O.T.) engine operationWhen the engine is started, the MCU determines whichmode of operation (closed loop or open loop) is correct. Itcan determine this by monitoring the input signals from thevarious input components. Air and coolant temperatureinformation, engine rpm information and vacuum levels areall provided to the MCU for this determination.The MCU operates the system in the open loop mode basedon a priority rating for the various predetermined engineoperating conditions. It continues to operate the system andoutput components in the open loop mode until such time