Specifications, Service and Repair of Farm and Lawn Tractors

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Kubota L3301, L3560, L3901 - Diesel Engine

Kubota D1803 3-cylinder diesel engine used in L3301, L3560, L3901 tractors.

Kubota L3301, L3560, L3901 - Cooling System

In addition to improving the cooling performance of the radiator by utilizing a bottom bypass system, the mechanism uses a 3-stage thermostat valve that reduces thermal shock considerably compared to previous radiators. When the coolant inside a Kubota D1803 engine is cool, the thermostat stays closed and coolant circulates inside the engine via the bypass pipe. When the temperature of the coolant exceeds the opening temperature of the thermostat, the thermostat opens in three stages, sending the now hot coolant to the radiator. Further, when the thermostat is fully open, it is structured so the hot coolant does not flow into the engine via the bypass circuit, thus increasing the cooling performance of the system.

Radiator Water Leakage

Fill a specified quantity of water into the radiator. Set a radiator tester and an adaptor on the radiator. Increase the water pressure to the specified pressure with the radiator tester and adaptor. Examine the radiator for water leakage. For water leakages from the pinhole, replace the radiator or repair with the radiator cement. When water leak is too much, replace the radiator.

Opening-temperature of Thermostat Valve

Push down the thermostat valve and put the thread between the valve and the valve seat. Put the thermostat and the thermometer in the container and increase the temperature of the water gradually. Take the thread, and float the thermostat in the water. As the water temperature rises, the valve will open, and the thermostat will separate from the thread. Measure the temperature at this moment. Continue to increase the temperature and read the temperature when the valve opens approximately 8 mm (0.3 in.).

Checking Coolant Level

Check to see that the coolant level is between the FULL and LOW marks of recovery tank. When the coolant level drops due to evaporation, add water only up to the full level. In case of leakage, add anti-freeze and water in the specified mixing ratio up to the full level. If the radiator cap has to be removed, follow the caution above and securely retighten the cap. Use clean, fresh water and anti-freeze to fill the recovery tank.

Cleaning Grill, Radiator Screen and Oil Cooler

Before checking or cleaning the radiator screen, stop the engine and wait long enough until it is cooled down. Check front grill and side screens to be sure they are clean of debris. Detach the front skirt. Detach the screen and remove all foreign materials. Grill and screen must be clean from debris to prevent engine from overheating and to allow good air intake for the air cleaner.

Kubota L3301, L3560, L3901 - Fuel System

Fuel cooler

The fuel cooler is set downstream of the separator and is used to cool the fuel. When the pressure of fuel is increased, the temperature also rises. The fuel in the common rail system is raised to high pressure so the fuel temperature also rises. If the fuel temperature rises too much, output and durability are reduced. A fuel cooler that suppresses fuel temperature rise is provided to prevent this.

Feed pump



The feed pump is installed after the fuel cooler and has a function of suctioning fuel from the fuel tank and pressure feeding it through a filter and to the supply pump. Also, the feed pump is provided with a priming pump. This is for air removal through the supply pump through manual operation of the priming pump. Operating - During the up stroke, the piston is pushed up by the fuel cam via the tappet and push rod. As a result, the pressure in the inner chamber rises, the suction side check valve closes and the discharge side check valve opens. On the other hand, the pressure in the outer chamber is lowered so the suction side check valve opens and discharge side check valve closes. During the down stroke the piston is lowered by a piston spring and the pressure in the inner chamber is lowered so the suction side check valve opens and discharge side check valve closes. On the other hand, the pressure in the outer chamber rises so the suction side check valve closes and discharge side check valve opens.

Supply pump

The supply pump corresponds to conventional injection pumps but pressurizes the fuel to more than 2 times that of conventional pumps for delivery to the rail. The supply pump is made up of an intake adjustment valve (SCV), pressurizing part, overflow valve, IO valve, and zero delivery drain.

Cleaning Air Cleaner Primary Element

Remove the air cleaner cover and primary element. Clean the primary element: When dry dust adheres to the element, blow compressed air from the inside turning the element. Pressure of compressed air must be under 205 kPa (2.1 kgf/cm2, 30 psi). When carbon or oil adheres to the element, soak the element in detergent for 15 minutes then wash it several times in water, rinse with clean water and dry it naturally. After element is fully dried, inspect inside of the element with a light and check if it is damaged or not. Replace air cleaner primary element: Once yearly or after every six times of cleaning, whichever comes first.

Cleaning Inner Air Filter (Cabin Type)

Press the inner air filter in the arrow-marked directions to unlock it and remove the inner filter, and blow air from the direction opposite to the filter's normal air flow. Pressure of compressed air must be under 205 kPa (2.1 kgf/cm2, 30 psi).

Kubota L3301, L3560, L3901 - Replacing Fuel Filter

Remove the fuel filter. Put a film of clean fuel on rubber seal of new filter. Tighten the filter quickly until it contacts the mounting surface. Tighten filter by hand an additional 1/2 turn only. Bleed the fuel system.

Bleeding Fuel System

Air must be removed: When the fuel filter or lines are removed. When water is drained from water separator. When tank is completely empty. After the tractor has not been used for a long period of time. Fill the fuel tank with fuel, and open the fuel valve. Loosen the air vent plug on the fuel filter turns or so. Turn on the key switch and wait for about 1 minute. Then tighten up the air vent plug. Set the hand throttle lever at the minimum speed position and turn the key to START position. If the engine does not start, try it several times at 30 second intervals. Do not hold key switch at engine start position for more than 10 seconds continuously. If more engine cranking is needed, try again after 30 seconds. Accelerate the engine to remove the small portion of air left in the fuel system. If air still remains and the engine stops, repeat the above steps.

Cleaning Fresh Air Filter (Cabin Type)

Remove the knob bolts and pull out the fresh air filter. Attach the filter and cover. Normal use - Blow air from the opposite direction to the filter's normal air flow. Pressure of compressed air must be under 205 kPa (2.1 kgf/cm2, 30 psi). If the filter is very dirty: Dip the filter in lukewarm water with mild dish washing detergent. Move it up and down as well as left and right to loosen dirt. Rinse the filter with clean water and let it air-dry.

Kubota L3301, L3560, L3901 - EGR System

The EGR (Exhaust Gas Recirculation) system is a device that captures a part of the exhaust gas and returns it to the intake side reducing the amount of oxygen entering the engine and lowers combustion temperature suppressing generation of nitrogen oxides (NOx). The EGR being used on this engine is electronic and is made up of an EGR cooler, EGR lift sensor, EGR valve motor, and reed valve. The exhaust gas that is returned to the intake side (hereafter EGR gas) is cooled in the EGR cooler, adjusted to a suitable flow by an EGR valve motor that is controlled by the engine ECU, and is sent to the intake manifold. The reed valve prevents reverse flow of air from the air cleaner to the EGR valve motor.

EGR cooler



The EGR (Exhaust Gas Recirculation) cooler is used to lower combustion temperature and efficiently cool EGR gas, with the aim of reducing the NOx that is in the exhaust gas of Kubota D1803 diesel engine. The EGR cooler is set between the cylinder head and the EGR valve and returns the cooled exhaust gases to the engine suction side. The EGR cooler has resistant to clogging up, compact and efficient tubes internally.

Reed valve

The reed valves are set at the point where exhaust gases that have passed through the EGR valve mix with intake air and they prevent air on the air cleaner side from flowing to the EGR cooler side. These thin plate springs (reed valves) mounted at the bottom of the EGR valve motor open and close the EGR gas passage (during intake: reed valve is closed; during exhaust: open) and prevent the intake air from back flowing to the exhaust side.

Kubota L3301, L3560, L3901 - EGR Valve

Water Cooled EGR Valve - This is a device that regulates EGR gas flow. The degree the valve is open is detected using a lift sensor and a motor is used to set this to the degree of open calculated using signals including the engine speed. Also, passing engine coolant through the housing enables controlling temperature rise of the EGR valve.

EGR Cooler (Exhaust gas passage)

Block the EGR cooler exhaust gas outlet. Attach an air hose to the EGR cooler exhaust gas inlet and then submerge it in a water tank. Check that the coolant passage is full of water. Apply the specified amount of air pressure (290 kPa, 3.0 kgf/cm2, 43 psi) to the air hose side, and check that there are no air leaks in any of the EGR cooler parts. If there are air leaks, replace the EGR cooler. Block the EGR cooler exhaust gas inlet, EGR cooler exhaust gas outlet, and the coolant outlet. Attach an air hose to the EGR cooler coolant inlet, and then submerge it in a water tank. Apply the specified amount of air pressure (250 kPa, 2.5 kgf/cm2, 36 psi) to the air hose side, and check that there are no air leaks in any of the EGR cooler parts. If there are air leaks, replace the EGR cooler.

Checking and Cleaning EGR System

Perform an EGR actuation test. Based on test results, check that the EGR valve gas passage and coolant passage are not clogged. Clean any soot from the gas passage so that it does not damage the EGR valve. Clean the coolant passage by running it with water.

Checking Exhaust Manifold

Examine the exhaust manifold for crack, exhaust gas leakage and loose mounting screw. If you find a crack, change the exhaust manifold. If you find a gas leakage, tighten the mounting screw again or replace the gasket with a new one. If you find a loose mounting screw, tighten the mounting screw again.

Kubota L3301, L3560, L3901 - Lubricating System

Checking Engine Oil Level

Park the machine on a flat surface. Check engine oil before starting the engine or 5 minutes or more after the engine has stopped. To check the oil level, draw out the dipstick, wipe it clean, replace it, and draw it out again. Check to see that the oil level lies between the two notches. If the level is too low, add new oil to the prescribed level at the oil inlet.

Changing Engine Oil

To drain the used oil, remove the drain plug at the bottom of the engine and drain the oil completely into the oil pan. All the used oil can be drained out easily when the engine is still warm. After draining reinstall the drain plug. Fill with the new oil up to the upper notch on the dipstick. Use DPF-compatible oil (CJ-4) for Kubota D1803 engine.



Replacing Engine Oil Filter

Remove the oil filter. Put a film of clean engine oil on the rubber seal of the new filter. Tighten the filter quickly until it contacts the mounting surface. Tighten filter by hand an additional 1/2 turn only. After the new filter has been replaced, the engine oil normally decreases a little. Make sure that the engine oil does not leak through the seal and be sure to check the oil level on the dipstick. Then, replenish the engine oil up to the prescribed level.

Lubricating Grease Fitting

Apply a small amount of multipurpose grease to the following points every 50 hours. If you operated the machine in extremely wet and muddy conditions, lubricate grease fittings more often. When apply a grease to forward front axle support, remove the breather plug and apply a grease until grease overflows from breather plug port. After greasing reinstall the breather plug.

Replacing Oil Separator Element

Remove the cover and take out the element. Wipe off oil and the carbon in the case with a clean rag. Fit a new oil separator element. Tighten the cover.

Kubota L3301, L3560, L3901 - Electrical System

Starter

Motor Test - Disconnect the battery negative cable from the battery. Disconnect the battery positive cable and the leads from the starter B terminal. Remove the starter from the engine. Disconnect the connecting lead from the starter C terminal. Connect a jumper lead from the connecting lead to the battery positive terminal post. Connect a jumper lead momentarily between the starter motor housing and the battery negative terminal post. If the motor dose not run, check the motor. Magnetic Switch Test - Disconnect the battery negative cable from the battery. Disconnect the battery positive cable and the leads from the starter B terminal. Remove the starter from the engine. Disconnect the connecting lead from the starter C terminal. Connect a jumper lead from the starter S terminal to the battery positive terminal post. Connect a jumper lead momentarily between the starter C terminal and the battery negative terminal post. If the pinion gear dose not pop out, check the magnetic switch.

Glow Plug

Lead Terminal Voltage - Disconnect the wiring lead from the glow plug after turning the main switch off. Turn the main switch key to the PREHEAT position, and measure the voltage between the lead terminal and the chassis. Turn the main switch key to the START position, and measure the voltage with a voltmeter between the lead terminal and the chassis. If the voltage at either position differs from the battery voltage, the wiring harness or main switch is faulty. Glow Plug Continuity - Disconnect the lead from the glow plugs. Measure the resistance with an ohmmeter between the glow plug terminal and the engine body. If 0 ohm is indicated, the screw at the tip of the glow plug and the housing are short-circuited. If the factory specification is not indicated, the glow plug is faulty.

Engine Stop Solenoid

Connector Voltage - Disconnect the 2P connector from engine stop solenoid. Turn the main switch key to the ON position. Measure the voltage with voltmeter between the terminal (Black / White), terminal (White / Black) and Body. If the voltage differs from the battery voltage, the wiring harness or main switch is faulty. Stop Solenoid Coil - Disconnect the 2P connector from engine stop solenoid. Measure the resistance with an ohmmeter between the terminal 1, terminal 2 and body. If resistance differs from the factory specification, the coil is faulty.

Kubota L3301, L3560, L3901 - Separating Clutch Housing and engine

Steering Joint Shaft

Remove the steering joint screw. Remove the steering joint cover and the steering joint support. Remove the steering joint shaft.

Fuel Tanks

Remove the left step. Remove the fuel hose cover. Remove the brake rod L.H. Place the disassembling stands under the right and left fuel tanks. Remove the front and rear support mounting screws of the right and left fuel tanks. Lower the fuel tanks together with the disassembling stands. Disconnect the fuel hoses, overflow hose and fuel level sensor connector from the fuel tank L.H. Disconnect the fuel hose from the fuel tank R.H.

Wiring Harness

Remove the harness clamps and harness cover. Disconnect the battery positive cable and battery. Remove the slow blow fuse box. Disconnect the alternator terminal B and terminal IG. Disconnect the oil pressure switch connector, starter terminal B and terminal ST. Disconnect the DPF temperature sensor connectors and differential pressure connector. Disconnect the injector connectors and glow plug connector. Disconnect CCV GND wiring harness, CCV relay, CCV heater fuse, CCV SB fuse and CCV heater.

Sensor Connectors

Disconnect the air flow sensor connector, intake throttle sensor connector, electromagnetic pump connector and EGR valve connector. Disconnect the common rail sensor connector, suction control valve connector and camshaft position sensor connector. Disconnect the crankshaft position sensor connector. Set aside the main harness to the rear.

Steering and Panel Cover

Remove the steering wheel. Remove the mat. Remove the steering post cover 2 and steering post cover 1. Remove the meter panel cover.

Propeller Shaft

Slide the propeller shaft cover after removing the screws. Tap out the spring pins and slide the couplings and then remove the propeller shaft with covers. Apply grease to the splines of propeller shaft.

Separating Kubota D1803 Engine from Clutch Housing

Place the disassembling stands under the engine and clutch housing. Remove the engine and clutch housing mounting screws and nuts. Separate the engine and clutch housing. Apply grease to the spline of clutch shaft. Apply liquid gasket to joint face of the flywheel housing and clutch housing.

Radiator Assembly and DPF Muffler

Remove the air cleaner together with air cleaner hoses and bracket. Remove the muffler pipe, muffler flange mounting screws and DPF muffler together with DPF muffler bracket. Remove the oil separator. Disconnect the radiator hoses. Disconnect the fuel cooler hoses. Remove the radiator together with front support.

Fuel Hoses and Pillar

Disconnect the overflow hose and fuel hoses, then remove the bracket together with fuel sub tank. Disconnect the overflow hose, fuel hose, then remove the fuel filter. Disconnect the power steering return hose and fuel hose. Remove the power steering delivery pipe. Remove the dipstick stay. Remove the pillar.

Turbocharger

Disconnect the air intake hose. Remove the fan belt and alternator. Remove the EGR cooler hose and cooler pipe. Disconnect the oil pipe and return hose. Remove the exhaust manifold together with turbocharger. Be sure to adjust the fan belt tension.

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