General Information

NOTE: For current engines, the first two characters of the serial number stand for the engine family and type. LD stands for a naturally aspirated 4.236 Engine. LH stands for a compensated (turbocharged) 4.236 Engine. The next five characters are the parts list number. These five characters are represented by dashes "-" in this module. The next single letter is the country of origin. The next set of numbers is the production serial number, and the last letter is the year of manufacture.

Engine Design

Type ... Four Cylinder, Four Stroke

Combustion System ... Direct Injection

Nominal Bore ... 98.43 mm (3.875 in)

Stroke ... 127 mm (5 in)

Cubic Capacity ... 3.86 liters (236 cu in)

Compression Ratio

4.236 Engines ... 18 to 1

C4.236 Engines ... 16 to 1

Number and Arrangement of Cylinders (as seen from front of engine) ... 1-2-3-4

Firing Order ... 1-3-4-2

Rotation of crankshaft (as seen from front of engine) ... Clockwise

Rotation of crankshaft (as seen from front of engine) ... Clockwise

The left side and right side of engine are as seen from flywheel end. No. 1 cylinder is the front cylinder of the engine.

Engine Serial Numbers

Engine Serial Number Location

The engine serial number is located on the left hand side of the block above the fuel injection pump.

For current engines, the first two characters of the serial number stand for the engine family and type. LD stands for a naturally aspirated 4.236 Engine. LH stands for a compensated (turbocharged) 4.236 Engine. The next five characters are the parts list number. The next single letter is the country of origin. The next set of numbers is the production serial number, and the last letter is the year of manufacture.

Some new components and improvements have introduced on the 4.236 engine. If there is a difference in service or specifications, it is noted in this module. Engine numbers beginning with LD70179, LD70200, LD70201, LH70189, LH70202 or LH70213 will have the new components and improvements at first production. On 416 Backhoe Loader Engines (engine numbers beginning with LD70178), the engine cut-in serial numbers are given for the changes if available. Following are the numbers that are used in the Backhoe Loaders:

LD70178, LD70200 (metric interfacing ... 416 with 4.236 engine

LD70179, LD70201 (metric interfacing) ... 426 and 428 with 4.236 engine

LH70189, LH70202 (metric interfacing) ... 416, 426 and 428 with C4.236 engine

LH70213 (metric interfacing) ... 436 and 438 with 4.236 engine

Fuel System

Basic Fuel System Diagram
(1) Fuel injectors (atomisers). (2) Fuel return line from injectors. (3) Fuel filter. (4) Fuel return line to tank. (5) Tee. (6) Fuel return line from fuel injection pump. (7) Fuel supply line to injection pump. (8) Fuel lift pump. (9) Water separator. (10) Fuel injection pump. (11) High pressure fuel lines. (12) Fuel tank.

When the engine is turning, fuel is pulled from fuel tank (12) through water separator (9) by fuel lift pump (8). When the fuel goes through the water separator, any water in the fuel will go to bottom of the bowl. The fuel lift pump sends the fuel at low pressure to fuel filter (3). From the fuel filter, the fuel goes through line (7) to fuel injection pump (10). The fuel injection pump sends high pressure fuel through lines (11) to each fuel injector (1), and the fuel injector sprays fuel into the cylinder. Fuel not used by the injection pump goes through line (6) to tee (5) and through line (4) back to fuel tank (12). There is a controlled flow valve installed in the fuel return fitting of the fuel injection pump to prevent fuel from going back into the fuel pump from the return line.

Leakage from the fuel injectors flows through line (2) to the top of fuel filter (3). Return fuel flows from injectors (1), fuel filter (3) to tee (5) and through line (4) back to fuel tank (12).

High pressure fuel lines (11) are connected to pressurizer valves at high pressure outlets 1, 3 and 4 of the fuel injection pump. The check valves keep pressurized fuel in the line. This fuel is so there will be no delay of the start of injection. The number 2 high pressure outlet does not have a pressurizer valve. This is to aid in hot starts.

The fuel injection pump needs fuel for lubrication. The precision parts of the pump are easily damaged. The system must be primed any time any part of the system is drained of fuel. For example, when the fuel filter is changed or a fuel line is removed, the inspection cover on the fuel injection pump is removed to check timing, or the injection pump is removed for service or repair, the fuel system must be primed (air removed).

Fuel System Components (Left Side)
(1) Fuel injector. (2) Fuel return line from injectors. (3) Fuel filter. (5) Tee. (6) Fuel return line from fuel injection pump. (7) Fuel supply line to fuel injection pump. (10) Fuel injection pump. (11) High pressure fuel lines.

Fuel System Components (Right Side)
(8) Fuel lift pump. (9) Water separator.

There is a small screen in fuel lift pump (8). The pump also has a lever to prime the fuel system (remove the air).

Fuel Injector Operation

Fuel Injector
(1) Fuel inlet from fuel injection pump. (3) Outlet for return fuel (leakage). (5) Compression spring. (6) Body. (8) Nozzle cap nut. (9) Needle valve. (10) Nozzle. (11) Orifices (four).

Fuel, under high pressure from the fuel injection pump, goes through the hole in fuel inlet (1). The fuel then goes around needle valve (9), fills the inside of nozzle (10) with fuel and pushes against valve (9) and compression spring (5). When the force made by the pressure of the fuel is more than the force of spring (5), valve (9) will lift. When needle valve (9) lifts, fuel under high pressure will go through four orifices (11) into the cylinder. When the fuel is sent to the cylinder, the force made by the pressure of the fuel in the nozzle body will become less. The force of spring (5) will then be more than the force of the pressure of the fuel in the nozzle body. Valve (9) will move quickly to the closed position.

Needle valve (9) is a close fit with the inside of the nozzle and makes a positive seal for the valve.

When the fuel is sent to the cylinder, a small quantity of fuel will leak by the valve guide. This fuel gives lubrication to the moving parts of the fuel injection nozzle. This fuel then goes through a leakoff passage in body (6) to outlet (3) and is returned to the fuel tank.

Fuel Injection Pump

Fuel Injection Pump Components
(1) Fuel return passage check valve. (2) Fuel return passage. (3) Fuel shutoff lever. (4) Low idle stop screw. (5) Accelerator lever. (6) Control mechanism. (7) High idle stop screw (behind sleeve). (8) Metering valve. (9) Pressurizer valve (three). (10) Fuel outlet passage (to injectors). (11) Hydraulic head. (12) Drive shaft assembly. (13) Fuel inlet passage. (14) Fuel inlet filter. (15) Pump body. (16) Flywheel assembly. (17) Governor assembly. (18) Drive plate. (19) Plungers. (20) Automatic advance mechanism. (21) Fuel shutoff solenoid. (22) Rotor assembly. (23) Transfer pump. (24) Regulator valve.

The fuel injection pump is a totally enclosed and pressurized system. The pump is of the single cylinder opposed plunger type and uses inlet metering at low pressure to control the volume of the high pressure fuel injection charges.

A rotor turns inside the closely fit stationary cylindrical body and functions as a pump and distributor rotor. The opposed pump plungers carried in the rotor have displacement outward on the fill stroke because of internal fuel pressure. The pump plungers are driven inward on the pump stroke by the action of a stationary cam ring in the body of the pump.

The fuel injection pump sends the correct amount of high pressure fuel through injection nozzles, to individual cylinders at the correct time (near end of compression stroke). The injection pump meters (measures) amount of fuel delivered to the nozzles. This action controls engine speed by the governor setting or position of the accelerator or throttle control.

Fuel Injection Pump

The fuel lines to the fuel injectors are of equal length to make sure pressure is even, and correct injection timing for each nozzle is present.

During operation, extra fuel which is used as coolant and lubricant for pump parts that move is circulated through the pump housing and returned to the tank. Return lines also carry away any air trapped in the nozzles or pump housing.

The fuel is turned off by fuel shutoff solenoid (21), which is mounted to the back of the fuel injection pump. All models also have fuel shutoff lever (3) so the engine can be shutdown manually if the solenoid fails.

Operation

Fuel Injection Pump Rotor Assembly
(19) Plungers. (20) Automatic timing advance mechanism. (22) Rotor assembly. (25) Cam ring. (26) Shoes. (27) Rollers.

Internal cam ring (25) in the pump housing has four lobes and operates opposite pump plungers (19) through cam rollers (27) carried in shoes (26) that slide in the rotor body. Plungers (19) are forced inward at the same time as rollers (27) contact the opposed cam lobes. This is the injection stroke. The plungers are returned by pressure of the inlet fuel and this forms the charging stroke.

Rotor assembly (22) is driven by the engine through the pump drive gear and hub.

The space of the cam lobes and delivery ports make sure the timing interval between injections is exactly equal.

Plunger On Inlet Stroke
(13) Fuel inlet passage. (19) Plungers. (22) Rotor assembly.

Fuel that enters the pump through inlet passage (13) and filter (14) is pressurized by a sliding vane type transfer pump on the rotor inside the hydraulic head. The pressure rise is controlled by regulator valve (24) in the end plate of the pump. The fuel then flows through the passages to the pump elements.

The outward travel of the opposed pump plunger is controlled by the quantity of metered fuel, which is variable in relation to the setting of the metering valve. As a result, the rollers which operate the plungers do not follow the contour (shape) of the internal cam ring but contact the cam lobes at points which vary in relation to the degree of plunger displacement. The maximum amount of fuel delivered is regulated by limited outward travel of the plungers by an adjustable stop.

Plunger On Injection Stroke
(10) Fuel outlet passage. (19) Plungers. (22) Rotor assembly.

As rotor assembly (22) turns, inlet passage (13) is cut off and the single distributor port in the rotor is in alignment with outlet passage (10) in the hydraulic head. At the same time, the plungers are forced inward by the rollers contacting the cam lobes, and fuel injection pressure passes up the center bore of the rotor through passage (10) to one of the injectors. The rotor has four inlet ports and there are four outlet ports in the hydraulic head.

The cam lobes have a contour (shape) that gives pressure relief in the injection lines at the end of the injection cycle. This gives a sharp cut-off of fuel and prevents "dribble" (leakage) at the nozzles.

Governor assembly (17) is fastened on drive shaft assembly (12) and is completely inside the pump body. Linkage causes the movement of the governor flyweights to move the control lever on metering valve (8). Governor control mechanism (6) is enclosed in a housing installed on the pump body.

Fuel Shutoff Solenoid

The fuel shutoff solenoid electrically turns the fuel supply to the fuel injection pump on or off. When the key start switch is in the START or RUN position, current flows through windings (29) in the solenoid.

Fuel Shutoff Solenoid Location
(21) Fuel shutoff solenoid.

Fuel Shutoff Solenoid
(15) Fuel injection pump body. (21) Fuel shutoff solenoid. (28) Spring. (29) Winding. (30) Plunger. (31) Fuel passage from transfer pump. (32) Fuel passage to metering valve.

Current flow in the windings makes a magnetic force which lifts plunger (30) off its seat in pump body (15). This lets fuel flow in passage (31) and out passage (32) to the metering valve.

When the ignition switch is turned OFF, current does not flow in windings (29). Spring (28) pushes plunger (30) against its seat in body (15) and closes fuel passage (32) to the metering valve. No fuel is injected into the engine cylinders, and the engine stops.

Ether Starting Aid

Ether Starting Aid
(1) Ether valve assembly. (2) Tube.

The diesel engine is equipped with an ether starting aid. It helps the engine start in cold weather. Ether valve assembly (1) is mounted inside the left hand loader tower. It has tube (2) which connects the valve assembly to a nozzle installed in the inlet manifold.

A coolant temperature switch, mounted on the water temperature regulator (thermostat) housing, makes a ground for the ether starting aid switch on the instrument panel. The switch is normally closed when the engine coolant is below 27°C (80°F). If the coolant temperature goes above 38°C (100°F), the switch opens. This prevents the application of ether to a hot engine.

When ether valve assembly (1) is activated by the switch on the instrument panel, a specific volume of ether is sent through tube (2) to the nozzle. The nozzle sends the ether into the inlet manifold to help start the engine.

Cooling System

Basic Cooling System Schematic
(1) Pressure cap. (2) Upper hose. (3) Water temperature regulator (thermostat) housing. (4) Radiator. (5) Cylinder head. (6) Water pump. (7) Cylinder block. (8) Lower hose. (9) Shunt line.

The down flow cooling system is the type with a radiator that will keep the engine cool with a water to air transfer (movement of the heat from water to the air). Water pump (6) is mounted on the front of cylinder block (7) and is driven by a V-belt from the crankshaft pulley. The inlet opening of the water pump is connected to lower hose (8). The outlet flow from the water pump goes through passages inside the cylinder block. The cooling system is equipped with shunt line (9). It is connected to the inlet opening of water pump (6) to keep positive water pressure in the water pump inlet opening at all times.

The coolant from the water pump through the cylinder block passages has primary coolant flow to and around the cylinder liners and then onto cylinder head (5) with coolant flow to and around the seats for the valves. This method gives the coolant with the coolest temperature flow to the hottest area during engine operation.

After the coolant goes through the cylinder head, it flows to water temperature regulator (thermostat) housing (3), where the bypass type water temperature regulator (thermostat) is installed. The regulator controls the opening to radiator (4) to control the cooling system temperature.

If the coolant is cold, the regulator will be closed. The coolant circulates from the water pump through the cylinder block and head until the temperature of the coolant is warm enough to make the regulator open. When the regulator opens, the coolant will go through upper radiator hose (2) and into the top tank of radiator (4). Coolant then flows through the cores of the radiator. The air from the fan cools the coolant as it flows to the bottom of the radiator and out hose (8) where the coolant returns to the water pump.

Most radiators are equipped with a shroud to increase the efficiency of the fan and cause the air to be pushed through the radiator and away from the machine.

The cooling system pressure is controlled by cap (1). When the cooling system pressure is above its rated pressure a valve opens in pressure cap (1) which releases the cooling system pressure to the atmosphere. After the engine is at normal temperature for operation, a development of vacuum is present in the cooling system.

Lubrication System

Oil Lubrication Schematic

Oil Pump
(1) Strainer. (2) Oil pump relief valve. (3) Oil pump. (4) Idler gear. (5) Crankshaft gear.

The lubrication system is the pressure type and the flow of oil goes from the oil pan through strainer (1) into oil pump (3). Oil pump (3) is driven by crankshaft gear (5) through idler gear (4). The oil pump is connected to the front main bearing cap. Relief valve (2) which is spring loaded controls the maximum oil pressure. An oil pressure sending unit is connected to the main oil gallery.

Oil under pressure goes from the oil pump through the relief valve and filter. On the C4.236 (Turbocharged) Engines, oil passes first through the oil cooler. The oil cooler is cooled by water from the cooling system. Oil flows through the filter to the main oil gallery which is a drilled passage the length of the crankcase.

Timing Gears
(6) Idler gear. (7) Idler gear retainer plate.

From the gallery the oil flows through drilled passages to the main bearing bores and then through the crankshaft passages to the big end (rod) bearings. The camshaft bearings are lubricated from numbers 1, 3 and 5 main bearings. The camshaft center bearing supplies a controlled amount of oil to the rocker shaft assembly. Oil from the rocker shaft drains through a bleed hole in each rocker lever to lubricate the valves and valve guides.

Oil also goes from the gallery through the rear of idler gear (6) hub, then through passages to lubricate the idler gear bushings and gear retainer plate (7).

Pistons, cylinder liners, connecting rod small end bushings, cam lobes and tappets (valve lifters) are splash and oil mist lubricated.

Air Inlet And Exhaust System

4.236 Engines

Air Inlet and Exhaust System Components
(1) Exhaust manifold. (2) Inlet manifold. (3) Engine cylinder.

The air inlet and exhaust system components on naturally aspirated engines are: the air cleaner, inlet manifold, air inlet hose, air indicator, cylinder head valves and valve mechanism components, exhaust manifold, pipe and muffler.

Air is pulled in the air inlet system by the intake stroke of the piston. The air flows in the air cleaner, through the air inlet hose that directs the volume of air to inlet manifold (2). The air flows through the inlet manifold which directs even distribution of the air to each cylinder (3), where the air is mixed with fuel from the injectors. The sequence and action of the engines' four cylinders and four strokes (compression, power, exhaust and intake) give constant air flow to the intake system for engine operation. The air indicator shows a red indication when too much air restriction (dirt) is in the air cleaner.

The action of the exhaust stroke and the timing of the valve mechanism pushes combustion fumes out of the open exhaust valve through exhaust manifold (1), pipe and muffler.

The valves and the valve mechanism control the flow of air and exhaust gases in the cylinder during engine operation.

The intake and exhaust valves are opened and closed by the rotation and movement of the crankshaft, camshaft, tappets (valve lifters), push rods, rocker arms and valve springs. Rotation of the camshaft gear is driven by and timed to the crankshaft gear through an idler gear. When the camshaft turns, the tappets (valve lifters) are moved up and down. This movement makes the push rods move the rocker arms, which in turn makes the intake and exhaust valves open and close according to the firing order of the engine. The valve springs push the valves back to the closed position.

There is one intake and one exhaust valve for each cylinder. An exhaust valve seat can be installed in the cylinder head for service. The valve seat for the intake valve is machined into the cylinder head and cannot be removed.

The valve guides are machined into and are part of the cylinder head on earlier engines. Current engines have replaceable valve guides.

C4.236 (Turbocharged) Engines

Air Inlet and Exhaust System
(1) Turbocharger turbine wheel. (2) Turbocharger compressor wheel. (3) Exhaust outlet. (4) Air inlet. (5) Exhaust manifold. (6) Inlet manifold. (7) Engine cylinder.

The air inlet and exhaust system components for the C4.236 (Turbocharged) Engines are the same as naturally aspirated engines except for the addition of a turbocharger and its piping.

Clean inlet air from the air cleaner is pulled through air inlet (4) of the turbocharger by the turning compressor wheel (2). The compressor wheel causes a compression of the air. The air then goes to inlet manifold (6) of the engine. When the intake valves open, the air goes into engine cylinder (7) and is mixed with the fuel for combustion. When the exhaust valves open, the exhaust gases go out of the engine cylinder and into exhaust manifold (5). From the exhaust manifold, the exhaust gases go through the blades of turbine wheel (1), This causes the turbine wheel and compressor wheel to turn. The exhaust gases then go out exhaust outlet (3) of the turbocharger.

Turbocharger

Turbocharger
(1) Turbine wheel. (2) Compressor wheel. (3) Exhaust outlet. (4) Air inlet. (8) Oil inlet passage. (9) Oil outlet. (10) Exhaust inlet.

The turbocharger is installed on the exhaust manifold. All the exhaust gases from the engine go through the turbocharger.

The exhaust gases enter exhaust inlet (10) and go through the blades of turbine wheel (1), causing the turbine wheel and compressor wheel (2) to turn.

When the compressor wheel turns, it pulls filtered air from the air cleaner through air inlet (4). The air is put in compression by action of the compressor wheel and is pushed to the inlet manifold of the engine.

When engine load increases, more fuel is injected into the engine cylinders. The volume of exhaust gas increases, which causes the turbocharger turbine wheel and compressor wheel to turn faster. The increased rpm of the compressor wheel increases the quantity of inlet air. As the turbocharger provides additional inlet air, more fuel can be burned. This results in more horsepower from the engine at higher altitudes.

Maximum rpm of the turbocharger is controlled by the high idle speed setting and the height above sea level at which the engine is operated.

The bearings for the turbocharger use engine oil for lubrication. The oil comes in through oil inlet (8) and goes through passages in the center section for lubrication of the bearings. Oil from the turbocharger goes out through oil outlet (9) in the bottom of the center section and goes back to the engine oil pan.

The turbocharger allows the engine to run properly at high altitudes where the air is leaner. In this application, the turbocharger does not give more power. It compensates for leaner air.

Crankcase Ventilation System

The air intake system is also equipped with a crankcase ventilation system, or breather. The piston intake stroke pulls in atmospheric air to the crankcase area.

Crankcase Ventilation
(1) Ventilation hose. (2) Breather.

The fumes in the crankcase flow through a passage of the engine block to the valve cover, through hose (1) and breather (2) to the atmosphere.

Electrical System

The electrical system is a 12 volt, negative ground system that has two basic circuits. They are the starting circuit and the charging circuit, which includes the low amperage circuit with warning lights and gauges. Some of the electrical components are used in more than one circuit.

The starting circuit is in operation only when the key start switch is turned to the START position. In the starting circuit, the transmission neutral/switch must be closed before the starter solenoid is energized (electrical energy).

The charging circuit is in operation when the engine is running. The alternator in the charging circuit gives current to the electrical system. The battery keeps the storage of the current. A voltage regulator in the circuit, on the alternator housing, controls the amount of current output to the battery. The voltmeter in the circuit shows system voltage.

Reference: For a complete electrical schematic, see Schematics For Backhoe Loader Electrical System, Form No. SENR3165; Backhoe Loader Electrical System (With Roading Arrangement), Form No. SENR3924; 416, 426, 436 & Series II Backhoe Loader Electrical System, Form No. SENR4783 and 428, 438 & Series II Backhoe Loader Electrical System, Form No. SENR4798.

Starting System

When the key start switch is in the START position, it sends power through the neutral/start switch to activate the start relay. The start relay sends power to the starting motor solenoid and starting motor. If the transmission is not in neutral (neutral/start switch open), the start relay is not activated.

When the key start switch is in the START or ON position, it sends current to energize the engine fuel shutoff (shutdown) solenoid. The solenoid must be energized to allow fuel to go to the engine. When the key switch is put in the OFF position, the solenoid is not energized and the engine is stopped.

Starting Motor

Basic Starting System Schematic

Starting Motor

For detailed Systems Operation information refer to the Bosch JF Series Starting Motors Module, Form No. SENR3550.

The starting motor is used to turn the engine flywheel fast enough to make the engine run.

The starting motor has a solenoid. When the key start switch is activated, voltage from the electrical system will cause the solenoid to move the starter pinion to engage with the ring gear on the flywheel of the engine. The pinion will engage with the ring gear before the electrical contacts in the solenoid close the circuit between the battery and the starting motor.

When the engine first begins to run, the clutch in the pinion drive assembly prevents damage to the armature. When the key start switch is released, the pinion will move away from the ring gear of the flywheel.

Starting Motor Solenoid

The starting motor solenoid is a solenoid switch that does two basic operations:

a. It closes the high current starting motor circuit with a low current relay circuit.

b. It engages the starting motor pinion with the ring gear.

The solenoid switch is made of an electromagnet with two sets of windings (pull-in coil and hold-in coil) around a hollow cylinder. There is a plunger with a spring load on it, inside the cylinder, that can move forward and backward. When current is sent through the windings, a magnetic field is made that pulls the plunger forward in the cylinder.

Key Start Switch in Start Position and Solenoid Switch Contacts Open

When current is first sent to the solenoid from the start relay, it goes two different ways:

Part of the current goes through the hold-in windings to ground.

The rest of the current goes through the pull-in windings and then through the starting motor windings to ground.

The magnetic fields, from the hold-in windings and from the pull-in windings, add together and start to move the cylinder. The shift lever, which is connected to the plunger, starts to move the pinion gear toward the ring gear. When the plunger has moved far enough to engage the pinion with the ring gear, it also makes contact between the switch contacts. This sends current from the battery to the starting motor, to turn it very fast.

Key Start Switch in Start Position and Solenoid Switch Contacts Closed

With the solenoid contacts closed, there is a short across the pull-in windings and no current goes through them. Only the magnetic field from the hold-in windings keeps the contacts closed and the pinion engaged with the ring gear.

Key Start Switch Released and Solenoid Switch Contacts Momentarily Closed

When the key start switch is released, there is no current through the hold-in windings from the start relay. The pull-in windings are no longer shorted. For a very short time current is sent from the solenoid switch contacts, through the pull-in windings in reverse direction, and on through the hold-in windings in the normal direction to ground. The magnetic fields made by the two sets of windings are opposite and of equal magnitude to each other and are therefore cancelled. The spring load on the plunger moves the plunger back to its original position. This moves the pinion away from the ring gear. It also opens the switch contacts so that current is no longer sent to the starting motor.

Charging System

Alternator

Basic Charging System Schematic

Alternator

For detailed Systems Operation information refer to the Bosch K1/N1 Series Alternators Module, Form No. SENR3685.

The alternator is an electrical and mechanical component driven by a belt from engine rotation. It is used to charge the storage battery during the engine operation. The alternator is cooled by the fan that is part of the alternator.

When the key start switch is in the ON or START position, current is sent through a limiting resistor and diode to the coil of the alternator. This provides the necessary field current for the alternator at start up. When the engine is running and the alternator has output, it supplies current to charge the batteries and to the rest of the vehicle circuits.