Jeep Engines - Oljeep

360 AMC V-8 (IGNITION SYSTEM) 4292.When the engine is operating under light load, thecarburetor throttle plates restrict airflow, causing arelatively lean mixture to enter the combustionchambers. Ignition must occur earlier because the leanmixture requires a longer time to burn. The vacuumignition advance mechanism is used for this purpose.When carburetor ported or manifold vacuum is high,the vacuum advance mechanism moves the pickup coilassembly several degrees opposite to the direction thedistributor is rotating. This causes the pickup coil toreact to the presence of the trigger wheel teeth earlier.This is referred to as vacuum ignition advance. Withlow vacuum operating conditions, such as wide openthrottle acceleration, a spring in the vacuum advancesmechanism pushes the pickup coil back to a position ofzero advance.Pickup Coil and Trigger WheelThe ignition coil primary circuit is opened and closedelectronically by the ignition module. The distributorpickup coil and trigger wheel provide the input signalfor the ignition module.The trigger wheel, which is installed on the distributorshaft, has one tooth for each engine cylinder. Thewheel is mounted so that the teeth rotate past thepickup coil one at a time.The pickup coil has a magnetic field that is intensifiedby the presence of ferrous metal (contains iron - can bepicked up with an ordinary magnet). The pickup coilreacts to the trigger wheel teeth as they pass. As atrigger wheel tooth approaches and passes the polepiece of the pickup coil, it reduces the reluctance(compared to air) to the magnetic field and increasesfield strength. Field strength decreases as the toothmoves away from the pole piece. This increase anddecrease of field strength induces an alternating current(pulse) into the pickup coil, which triggers the ignitionmodule. The ignition module opens and closes the coilprimary circuit according to the position of the triggerwheel teeth.There is no contact between the trigger wheel andpickup coil assembly. Because there is no wear, thedwell angle does not require adjustment. The dwellangle is determined electronically by the control unitand is not adjustable. When the ignition coil primarycircuit is switched open, the internal electronic timer inthe ignition module keeps the coil primary only longenough for the electromagnetic field within the coil tocollapse and the voltage to discharge. The ignitionmodule then automatically closes the coil primarycircuit. The period of time the circuit is closed isreferred to as dwell.3. Distributor CupThe central tower on the distributor cap is connecteddirectly to the high voltage at the coil. The currentflows through the spring-loaded contact on the rotor tothe carbon button in the cap. The rotor tip aligns witha contact in the cap that corresponds to the cylinder tobe ignited just as the ignition coil output high voltageis applied to the rotor. In this way, each spark plug is“fired” in turn.Remove the distributor cap and wipe it clean with adry, lint free cloth. Visually inspect the cap for cracks,carbon paths, broken towers, white deposits on theinside (caused by condensation entering the vehiclethrough cracks), and damaged rotor button. Replaceany cap that displays charred or eroded terminals. Themachined surface of a terminal end (faces towardrotor) will indicate some evidence of erosion fromnormal operation. Examine the terminal ends forevidence of mechanical interference with the rotor tip.If replacement of the distributor cap is necessary,transfer spark plug wires from the original cap to thenew cap one at a time. Ensure that each wire isinstalled into the tower of the new cap that correspondsto its tower position in the original cap. Fully seat thewires into the towers.4. Distributor RotorA unique feature of the SSI is the silicone applied tothe distributor rotor blade. Radio interference is greatlyreduced by the presence of a small quantity of siliconedielectric compound on the rotor blade. After a fewthousand miles, this compound becomes charred by thehigh voltage current flowing through the rotor. Thiscondition is normal. DO NOT scrape residue from therotor blade.When installing a replacement rotor, apply a thin coat0.75-3.0 mm (0.03-0.12”) of silicone dielectriccompound to the tip of the rotor blade.Visually inspect the rotor for cracks, evidence ofcorrosion and the effects of arcing on the metal tip, andevidence of mechanical interference with the cap.Some charring is normal on the end of the metal tip.The silicone dielectric compound applied to the rotortip for radio interference noise suppression (six-andeight-cylinder engines) will appear charred. This isnormal.DO NOT remove the charred compound. Test thespring for insufficient tension. Replace a rotor thatdisplays any of the adverse conditions. Coat the tip ofa replacement rotor with Mopar Silicone DielectricCompound or equivalent.