CJ2A Operation and Care
Manual -- Proper Maintenance 
(part 3 -- Engine Electricals, 
Fuel and Cooling Systems.)

The generator is a 35-ampere, two-brush unit which does not require adjustment to increase or decrease output.  This is accomplished by the regulator which limits the current generated to that which is required by the battery.  The generator charging rate, as shown by the ammeter, will be low when the battery is well charged and correspondingly higher as charging is required.

As a general rule it will not pay an owner, not equipped with specialized test equipment, to undertake generator repairs.  There are some adjustments which may be made without this equipment and which are covered below.

Should the generator stop charging, examine all connections in the charging line to be sure they are clean and tight.  Also note the condition of the commutator and brushes.  If the commutator is dirty and discoloured, it can be cleaned by holding a piece of No. 00 sand-paper against it with the engine running at idle speed.  Do not use emery or carborundum cloth.

The brushes must slide freely in their holders and should they be badly worn or oil soaked, they should be replaced.  Excessive arcing between the cummutator and brushes usually indicates incorrect seating of the brushes against the commutator or high mica insulation between the commutator segments.  Incorrect seating may be corrected by drawing a piece of No. 00 sand-paper around the commutator with the sanded side against the brush.  After sanding, blow the carbon dust and sand from the generator.

Should the above attention fail to make the unit operate satisfactorily, consult your Willys-Overland Dealer.

The regulator must be adjusted with great accuracy; hear as well as voltage and amperage must be considered when adjusting it.  Should trouble develop in the regulator either consult a Willys-Overland Dealer or install a new one.

The distributor delivers the spark to the right cylinder at the right time.  The mechanical breaker, built into the distributor, opens and closes the primary circuit at the exact time for ignition.  See Fig. 7 on the first page of Proper Maintenance.

The distributor cap should be kept clean for efficient operation.  It should be inspected periodically for cracks, carbon runners, evidence of arcing and badly corroded high tension terminals.  If any of these conditions exist, the cap should be replaced.

Inspect the distributor rotor for cracks or evidence of excessive burning at the end of the metal strip.  After a rotor has had normal use, the end of the metal strip will become burned.  If burning is found on top of the rotor, it indicates the rotor is too short and should be replaced.  Usually then this condition is found, the distributor cap segment will be burned on the horizontal face and the cap should also be replaced.

The distributor contact points should be kept clean and not burned or pitted.  The contact gap should be set at .020" (0.51 mm.).  When making adjustments, be sure that the fibre block in the breaker arm rests on one of the high points of the cam.  Adjust the points by loosening the lock screw and turning the eccentric head screw.  Recheck the gap after tightening the lock screw.

Should new contact points be installed they should be aligned so as to make contact at the centre of the contact surfaces.  Bend the stationary contact bracket to secure correct alignment and then recheck the gap.

Keep spark plug porcelains clean.  Dirty porcelains will cause hard engine starting and poor operation especially in damp weather.

The spark plug electrode gap should be set at .030" (0.76 mm.).  Too wide gap will cause misfiring, especially at high speeds and when operating with open throttle, while a small gap causes poor idling.  Uniform gap setting assures smooth engine operation.

It is recommended that spark plugs be replaced at intervals of each 10,000 miles of service for, because of erosion, the spark loses intensity.

The starting motor requires little attention except regular lubrication.  It is a standard three-bushing type motor with right-hand type Bendix spring.

It is not advisable to lubricate the Bendix drive shaft.  In use dirt and dust will cling to the Bendix shaft, if lubricated.  In time the shaft may become gummy, preventing engagement of the Bendix pinion with the fly-wheel ring gear, especially in cold weather.  Should the starting motor turn without turning the engine, remove the motor and wash the Bendix assembly thoroughly with cleaning solution.


The fuel system consists of the fuel tank lines, fuel pump, carburetor and air cleaner.  The most important maintenance attention is to keep the system clean and free of water, also periodically inspect for leaks.  Should the vehicle be stored for an extended period, the fuel system should be completely drained and the engine started and allowed to run until the carburetor is emptied.  This will avoid oxidation of the fuel, resulting in the formation of gum in the units of the system.

Gum formation is similar to hard varnish and may cause trouble in the fuel pump valves or the carburetor float valve may become stuck or the filter screen blocked.  Gum formation can be dissolved by acetone, obtainable in most drug stores.  In extreme cases, it will be necessary to disassemble and clean the fuel system, however, often one pint of acetone placed in the fuel tank with about one gallon of gasoline will dissolve any deposits as it passes through the system with the gasoline.

The Carter carburetor, Model W.O.-596S is a precision instrument designed to deliver the proper fuel and air mixtures at all engine speeds.  Carburetor parts wear little; the chief cause of faulty carburetor is blamed for poor engine performance when the trouble is elsewhere (see EMERGENCY CHART).  Do not disturb the carburetor until it is proven that the trouble is not elsewhere.  Should it be determined that the carburetor is at fault consult your Willys-Overland Dealer.

The carburetor is provided with an external adjustment to secure smooth engine idle.  Fig. 14, No. 15.  To set this adjustment, proceed asa follows:

Make sure that the choke is in a fully open position  Close the idle adjustment by turning it to the right or in against the seat; then open it one and one-quarter turns.  Start the engine and run it until operating temperature is obtained, then turn the adjustment in or out slightly until the engine fires evenly.  Open the throttle for a few seconds allowing the engine to clean the manifold.  Recheck the adjustment, then set the throttle stop screw at an idle speed of 600 tpm. or approximately 6 miles per hour in high gear.

1. Pump Operating Lever Assembly
2. Choke Valve Assembly
3. Choke Shaft and Lever Assembly
4. Metering Rod Spring
5. Nozzle
6. Nozzle, Retaining Plug
7. Metering Rod Disc
8. Neddle, Pin, Spring and Seat Assembly
9. Float and Lever Assembly
10. Low Speed Jet Assembly
11. Idle Well Jet
12. Metering Rod Jet and Gasket Assembly
13. Metering Rod
14. Nozzle Passage Plug and Gasket Assembly
15. Idle Adjustment Screw
16. Idle Adjustment Screw Spring
17. Idle Port Rivet Spring
18. Throttle Valve
19. Pump Jet
20. Pump Jet Strainer Nut
21. Pump Jet Strainer
22. Intake Ball Check Assembly
23. Discharge Disc Check Assembly
24. Pump Plunger Spring
25. Pump Plunger and Rod Assembly
26. Pump Arm Spring
27. Pump Connecting Link
28. Pump Arm and Collar Assembly

The engine is equipped with a fuel diffuser built as part of a thick insulting gasket which is installed between the carburetor and the intake manifold.  In operation the diffuser causes intense swirling of the fuel and air in the manifold.  Under some operating conditions this results in a drier and more satisfactory fuel mixture.

The fuel pump is of the diaphragm type attached to the left side of the crankcase and operated from an eccentric on the camshaft, Fig. 13.  The pump draws gasoline from the fuel tank, through a filtering screen mounted in the pump sediment chamber and forces it to the carburetor.  The pump pressure is 4 ½ lbs. at 16 above the outlet at 1800 rpm. Engine speed.

The sediment chamber can be removed by backing off the thumbscrew nut sufficiently to permit swinging the wire clamp to one side.  The bowl or cover should be washed and wiped dry and the screen dried and then cleaned with a stiff brush.  When reassembling the bowl, make certain that the cork gasket is not broken; reverse it and position it flat on the seat then install the bowl and tighten the thumb nut securely.  After cleaning, start the engine and carefully inspect the bowl to guard against leakage.

Lack of gasoline in the carburetor may be caused by the following conditions:

Should the carburetor flood (too much gasoline), check the unit to make certain that the needle valve Fig. 14, No. 8, is seating properly and that the float No. 9 is not stuck.

CAUTION:  Do not attempt repairs which require disassembling of the fuel pump other than cleaning as special care is required.  It is recommended that all fuel pump trouble be taken up with your Willys-Overland Dealer.

The capacity of the fuel tank is 10 ½ gal. (U.S.).  When filling the tank, care should be used that no foreign matter or water enters the tank.  Once each season, at a time when the fuel supply is low in the tank, remove the drain plug in the bottom to drain out sediment and water which may have accumulated.

The practice of checking the condition of the cooling system of you Jeep while lubricating it will guard against costly delays in service.  Inspecting the condition of the radiator and heater hoses; also the fan belt and water pump will eliminate the possibility of an overheated engine due to a water leak or loose fan belt.

The radiator is designed to cool the water under all operating conditions however, the core must be kept free from corrosion and scale and the air passages free of chaff, dust and mud.

At least twice a year flush out the cooling system.  A good way to do this is to remove the drain cock at the bottom of the radiator and that in the cylinder block under the generator.  Place a hose in the radiator filler opening and adjust the flow of water to equal that draining from the two openings.  Start the engine and allow it to run until the cooling system is thoroughly flushed.  After flushing it is advisable to install a corrosion inhibitor in the system to prevent rust and scale.  This may be obtained from your Willys-Overland Dealer.

Should the air passages become clogged, do not use a metal tool of any kind to clean them.  Use compressed air or water pressure and clean from the rear, forcing the dirt out through the front of the radiator.

The cap is of the pressure type, which prevents evaporation and loss of cooling solution.  A pressure up to 4 ½ pounds makes the engine more efficient by permitting a slightly higher operating temperature.  Vacuum in the radiator is relieved by a valve in the cap which opens at ½ to 1 pound vacuum.

To completely drain the cooling system, open both drain cocks; that at the bottom of the radiator and also in the cylinder block under the generator.  Remove the radiator cap to break any vacuum which might prevent thorough draining.

A 145º to 155º F. thermostat, Fig. 2, is used to provide quick warming and to prevent overcooling during normal vehicle operation.  The temperature at which this unit operates is set by the Manufacturer and can not be altered.  The thermostat should be checked first, should sudden overheating occur, as failure to operate will nearly block the water circulation.  As a check, remove the thermostat and if the overheating is eliminated, install a new one.

The heat indicator is of the hydraulic type and is connected to a bulb mounted in the water chamber of the cylinder head, by a capillary tube.  Should this unit fail to operate, it should be replaced as it is not practical to either repair or adjust it.

The water pump assembly Fig. 15 is a centrifugal impeller type, of large capacity to circulate the water in the entire cooling system.

The sealed type double-row ball bearing is integral with the shaft and is packed at the time of assembly with a special high melting point grease, so requires no lubrication.

The fan and generator are driven by a V-type belt.  The drive is on the sides of the belt, therefore it is not necessary to adjust it tight, which might cause excessive wear on the water pump and generator bearings.  Adjust the belt by swinging the generator away from the engine until the belt can be depressed 1 by thumb pressure midway between the pulleys.

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