________________________________________________________________________________

Kubota L2501, L3200, L3400, L3800 - Engine Service and Maintenance

Kubota L2501, L3200, L3400 tractors fitted with D1703 diesel engine. D1803 engine used in L3800 model.

Kubota L2501, L3200, L3400, L3800 - Engine Maintenance

Starting the Engine (normal)

Set the fuel lever to the "on" position. Place the engine stop lever to the "Start" position. Place the speed control lever at more than half "operation". Insert the key into the key switch and turn it to the "operation" position. Turn the starter switch to the "preheating" position to allow the glow lamp to redden. The glow lamp goes out in about 5 seconds when the lamp timer is up. Even with the glow lamp off, the glow plug can be preheated by turning the starter switch to the "preheating" position. Turn the key to the "Starting" position and the engine should start. Release the key immediately when a Kubota D1803 engine starts. Check to see that the oil pressure lamp and charge lamp are off. If the lamps are still on, immediately stop the engine, and determine the cause. If the oil pressure lamp should be still on, immediately stop the engine and check. If there is enough engine oil. If the engine oil has dirt in it. If the wiring is faulty. Warm up the engine at medium speed without load. If the engine does not catch or start at 10 seconds after the starter switch is set at "Starting" position, wait for another 30 seconds and then begin the engine starting sequence again. Do not allow the starter motor to run continuously for more than 20 seconds.

Cold weather starting

If the ambient temperature is below -5C (23F) and the engine is very cold, start it in the following manner: Set the fuel lever to the "ON" position. Place the engine stop lever to the "Start" position. Place the speed control lever at more than half "operation". Insert the key into the key switch and turn it to the "operation" position. Turn the key to the "preheating" position and keep it there for a certain period mentioned below. Turn the key to the "Starting" position and the engine should start. If the engine fails to start after 10 seconds, turn off the key for 5 to 30 seconds. Do not allow the starter motor to run continuously for more than 20 seconds. Be sure to warm up the engine, not only in winter, but also in warmer seasons. An insufficiently warmed-up engine can shorten its service life. When there is fear of temperature dropping below -15 C (5 F) detach the battery from the machine, and keep it indoors in a safe area, to be reinstalled just before the next operation.

Radiator Cooling water

If the coolant temperature warning lamp lights up or if steam or coolant does not stop squirting from the radiator overflow pipe, turn off the load and keep the engine idling (Cooling-Down) for at least 5 minutes to let it cool down gradually. Then stop the engine and take the following inspection and servicing. Check to see if the coolant runs short or if there is any coolant leak. Check to see if there is any obstacle around the cooling air inlet or outlet. Check to see if there is any dirt or dust between radiator fins and tube. Check to see if the fan belt is too loose. Check to see if radiator water pipe is clogged.

Color of exhaust - While Kubota D1703 engine is run within the rated output range: The color of exhaust remains colorless. If the output slightly exceeds the rated level, exhaust may become a little colored with the output level kept constant. If the engine is run continuously with dark exhaust emission, it may lead to trouble with the engine.

Immediately stop the engine if: The engine suddenly slows down or accelerates. Unusual noises are suddenly heard. Exhaust fumes suddenly become very dark. The oil pressure lamp or the water temperature alarm lamp lights up.

How to tell when the engine starts running backwards - Lubricating oil pressure drops sharply. Oil pressure warning light, if used, will light. Since the intake and exhaust sides are reversed, the sound of the engine changes, and exhaust gas will come out of the air cleaner. A louder knocking sound will be heard when the engine starts running backwards.

Remedies - Immediately set the engine stop lever to the "Stop" position to stop Kubota D1803 engine. After stopping the engine, check the air cleaner, intake rubber tube and other parts, and then replace parts as needed.

Air bleeding the fuel system

Air bleeding of the fuel system is required if: After the fuel filter and pipes have been detached and refitted; after the fuel tank has become empty; or before the engine is to be used after a long storage. Fill the fuel tank to the fullest extent. Open the fuel filter lever. Open the air vent cock on top of the fuel injection pump. Turn the engine, continue it for about 10 seconds, then stop it, or move the fuel feed pump lever by hand (optional). Close the air vent cock on top of the fuel injection pump. Always keep the air vent cock on the fuel injection pump closed except when air is vented, or it may cause the engine to stop. For fuel tanks that are lower than the injection pump. The fuel system must be pressurized by the fuel system electric fuel pump. If an electric fuel pump is not used, you must manually actuate the pump by lever to bleed. The primary fuel filter must be on the pressure side of the pump if the fuel tank is lower than the injection pump. To bleed, follow through above. Tighten air vent plug of the fuel injection pump except when bleeding, or it may stop the engine suddenly.

Checking the fuel pipes

Check the fuel pipes every 50 hours of operation. If the clamp band is loose, apply oil to the screw of the band, and tighten the band securely. If the fuel pipes, made of rubber, become worn out, replace them and clamp bands every 2 years. If the fuel pipes and clamp bands are found worn or damaged before 2 years pass, replace or repair them at once. After replacement of the pipes and bands, air-bleed the fuel system. When the fuel pipes are not installed, plug them at both ends with clean cloth or paper to prevent dirt from entering. Dirt in the pipes can cause fuel injection pump malfunction.

Kubota L2501, L3200, L3400, L3800 - Cleaning the fuel filter pot

Every 100 hours of operation, clean the fuel filter in a clean place to prevent dust intrusion. Close the fuel filter lever. Remove the top cap, and rinse the inside with diesel fuel. Take out the element, and rinse it with diesel fuel. After cleaning, reinstall the fuel filter, keeping out of dust and dirt. Air-bleed the injection pump. Entrance of dust and dirt can cause a malfunction of the fuel injection pump and the injection nozzle. Wash the fuel filter cup periodically.

Fuel filter cartridge replacement

Replace the fuel filter cartridge with a new one every 400 operating hours. Apply fuel oil thinly over the gasket and tighten the cartridge into position by hand-tightening only. Finally, vent the air. Replace the fuel filter cartridge periodically to prevent wear of the fuel injection pump plunger or the injection nozzle, due to dirt in the fuel.

Checking oil level and adding engine oil

Check the engine oil level before starting or more than 5 minutes after stopping Kubota D1803 engine. Remove the oil level gauge, wipe it clean and reinstall it. Take the oil level gauge out again, and check the oil level. If the oil level is too low, remove the oil filler plug, and add new oil to the prescribed level. After adding oil, wait more than 5 minutes and check the oil level again. It takes some time for the oil to drain down to the oil pan. Engine oil capacity - 7.5-9.5 L.

Changing engine oil

Change oil after the initial 50 hours of operation and every 200 hours thereafter. Remove the drain plug at the bottom of the engine, and drain all the old oil. Drain oil will drain easier when the oil is warm. Add new engine oil up to the upper limit of the oil level gauge.

Replacing the oil filter cartridge

Replace the oil filter cartridge. Apply a film of oil to the gasket for the new cartridge. Screw in the cartridge by hand. When the gasket contacts the seal surface, tighten the cartridge enough by hand. Because, if you tighten the cartridge with a wrench, it will be tightened too much. After the new cartridge has been replaced, the engine oil level normally decreases a little. Thus, run the engine for a while and check for oil leaks through the seal before checking the engine oil level. Add oil if necessary.

Kubota L2501, L3200, L3400, L3800 - Checking coolant level, adding coolant

Remove the radiator cap, after the engine has completely cooled, and check to see that coolant reaches the supply port. If the radiator is provided with a recovery tank, check the coolant level of the recovery tank. When it is between the "Full" and "Low" marks, the coolant will last for one day's work. When the coolant level drops due to evaporation, add water only up to the full level. Check to see that two drain cocks; one is at the crankcase side and the other is at the lower part of the radiator. If the radiator cap has to be removed, follow the caution and securely retighten the cap. If coolant should be leak, repair it or replace. Make sure that muddy or sea water does not enter the radiator. Use clean, fresh water and 50% anti-freeze to fill the recovery tank. Do not refill recovery tank with coolant over the "Full" level mark. Be sure to close the radiator cap securely. If the cap is loose or improperly closed, coolant may leak out and decrease quickly.

Remedies for quick decrease of coolant

Check any dust and dirt between the radiator fins and tube. If any, remove them from the fins and the tube. Check the tightness of the fan belt. If loose, tighten it securely. Check the internal blockage in the radiator hose. If scale forms in the hose, clean with the scale inhibitor or its equivalent.

Checking radiator hoses and clamp bands

Check to see if radiator hoses are properly fixed every 200 hours of operation or 6 months, whichever comes first. If hose clamps are loose or water leaks, tighten hose clamp securely. Replace hoses and tighten hose clamps securely, if radiator hoses are swollen, hardened or cracked. Replace hoses and hose clamps every 2 years or earlier, if checked and found that hoses are swollen, hardened or cracked. If the coolant temperature warning lamp lights up or if steam or coolant does not stop squirting from the radiator overflow pipe, turn off the load and keep the engine idling (Cooling-Down) for at least 5 minutes to let it cool down gradually. Then stop the engine and take the following inspection and servicing. Check to see if the coolant runs short or if there is any coolant leak. Check to see if there is any obstacle around the cooling air inlet or outlet. Check to see if there is any dirt or dust between radiator fins and tube. Check to see if the fan belt is too loose. Check to see if radiator water pipe is clogged.

Air cleaner

Since the air cleaner employed on this engine is a dry type, never apply oil to it. Open the evacuator valve once a week under ordinary conditions - or daily when used in a dusty place. This will get rid of large particles of dust and dirt. Wipe the inside air cleaner clean with cloth if it is dirty or wet. Avoid touching the element except when cleaning. 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). Replace the element every year or every 6 cleanings. Make sure the wing bolt for the element is tight enough. If it is loose, dust and dirt may be sucked in, wearing down the cylinder liner and piston ring earlier and thereby resulting in poor power output. Do not over service the air cleaner element. Over servicing may cause dirt to enter the engine causing premature wear. Use the dust indicator as a guide on when to service. Evacuator valve - Open the evacuator valve once a week under ordinary conditions - or daily when used in a dusty place - to get rid of large particles of dust and dirt. For the air cleaner with a dust cup (optional) - Remove and clean out the dust cup before it becomes half full with dust; usually once a week, or even every day if the working surroundings are dusty. Install the air cleaner dust cup with "top" indicated on the rear of the cup in the up position. (However, it may be installed in either direction when the cover is placed at the lower part.). If the dust cup is mounted incorrectly, dust or dirt does not collect in the cup, and direct attachments of the dust to the element will cause its lifetime to shorten to a great extent.

Adjusting Fan Belt Tension

Stop the engine and remove the key. Apply moderate thumb pressure to belt between the pulleys. If tension is incorrect, loosen the alternator mounting bolts and, using a lever placed between the alternator and the engine block, pull the alternator out until the deflection of the belt falls within acceptable limits. Replace fan belt if it is damaged. If belt is loosen or damaged and the fan is damaged, it could result in overheats or insufficient charging. Correct or replace belt.

Kubota L2501, L3200, L3400, L3800 - Service Engine

Top Clearance

Remove the cylinder head. With the piston at TDC, use grease to affix three or four plastigauges of a diameter 1.5 mm (0.059 in.) x 5.0 to 7.0 mm (0.20 to 0.27 in.) long to the crown of the piston; keep the gauges away from the intake valve and combustion chamber fittings. Take the piston to an intermediate position, install the cylinder head and tighten the head screws to the specified torque. Turn the crankshaft so the piston goes through TDC. Remove the cylinder head and compare the width of the crushed plastigauges with the scale. If they are out of spec, check the oil clearance of the crank pin, journals and piston pin. Top clearance - 0.60 to 0.70 mm / 0.024 to 0.027 in.

Valve Seating

Apply a thin layer of Prussian Blue on the valve face. Then put the valve on its seat to examine the contact. If the valve is not fully around the seat or the contact is less than 70 % of the factory specification, correct the valve seat. If the valve contact width cannot get the factory specification, replace the valve or correct the contact of the valve seat. Valve contact width - 2.12 mm / 0.0835 in.

Timing Gear Backlash

Set a dial indicator (lever type) with its point on the gear tooth. Hold the mating gear and move the gear to measure the backlash. If the backlash is more than the allowable limit, measure the oil clearance in the journal part of each shaft. If the oil clearance is correct, replace the gear. Backlash between idle gear and crank gear - 0.04150 to 0.1122 mm / 0.001634 to 0.004417 in. Backlash between idle gear and cam gear - 0.04150 to 0.1154 mm / 0.001634 to 0.004543 in. Backlash between idle gear and fuel supply pump gear - 0.04150 to 0.1154 mm / 0.001634 to 0.004543 in. Backlash between crank gear and oil pump gear - 0.04150 to 0.1090 mm / 0.001634 to 0.004291 in.

Replacement of Small End Bushing

Press out the used small end bushing with the replacing tool. Clean a new small end bushing and bore, and apply engine oil to them. Make sure that the oil hole of the connecting rod aligns the bushing hole. Then press fit the new bushing with the replacing tool.

Connecting Rod Alignment

Make sure that the oil clearance of the small end bushing is less than the allowable limit. Install the piston pin into the connecting rod. Install the connecting rod on the alignment tool of the connecting rod. Put a gauge on the piston pin, and move it against the face plate. If the gauge does not touch fully against the face plate, measure the space between the gauge pin and face plate. If the measurement is more than the allowable limit, replace the connecting rod. Connecting rod alignment - Allowable limit 0.05 mm / 0.002 in.

Side Clearance of Crankshaft

Set a dial indicator with its point on the end of the crankshaft. Move the crankshaft to the front and rear to measure the side clearance. If the measurement is more than the allowable limit, replace the thrust bearings. If the same dimension bearing is not applicable because of the crankshaft journal wear, replace it with an oversize one. Side clearance of crankshaft - 0.15 to 0.31 mm / 0.0059 to 0.012 in.

Crankshaft Bend

Hold the 2 end journals of crankshaft with V blocks on the surface plate. Set a dial indicator with its point on the middle journal. Turn the crankshaft slowly and read the variation on the indicator. If the measurement is more than the allowable limit, replace the crankshaft. Crankshaft bend - Allowable limit 0.03 mm / 0.001 in.

Kubota L2501, L3200, L3400, L3800 - Engine Troubleshooting

Engine is difficult to start or won't start

No fuel flow - Check the fuel tank and the fuel filter. Replace filter if necessary.

Air or water is in the fuel system - Check to see if the fuel line coupler bolt and nut are tight. Bleed the fuel system.

In winter, oil viscosity increases, and engine revolution is slow - Use oils of different viscosities, depending on ambient temperatures. Use engine block heater (Optional).

Battery becomes weak and the engine does not turn over quick enough - Clean battery cables and terminals. Charge the battery. In cold weather, always remove the battery from the engine, charge and store it indoors. Install it on the tractor only when the tractor is going to be used.

Insufficient engine power

Insufficient or dirty fuel - Check the fuel system.

The air cleaner is clogged - Clean or replace the element.

Kubota D1703 engine stops suddenly.

Insufficient fuel. Refuel. Bleed the fuel system if necessary.

Exhaust fumes are black colored

Fuel quality is poor - Change the fuel and fuel filter.

Too much oil - Check the proper amount of oil.

The air cleaner is clogged - Clean or replace the element.

Exhaust fumes are blue or white colored

The inside of exhaust muffler is dumped with fuel - Heat the muffler by applying load to the engine.

Injection nozzle trouble - Check the injection nozzle.

Fuel quality is poor - Change the fuel and fuel filter.

Kubota D1803 engine overheats

Engine overloaded - Shift to lower gear or reduce load.

Low coolant level Fill cooling system to the correct level; check radiator and hoses for loose connections or leaks.

Loose or defective fan belt - Adjust or replace fan belt.

Dirty radiator core or grille screens - Remove all trash.

Coolant flow route corroded - Flush cooling system.