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Kubota M4950 Troubleshooting

The Kubota M4950 utility tractor was manufactured from 1983 to 1993. This model has two version: M4950F (2WD) and M4950DT (4WD). The Kubota M4950 powertrain system components: a 170.3 cu.in (2.8 L) Kubota S2800-A six-cylinder liquid-cooled diesel engine and fully synchronized transmission with 12 forward and 4 reverse gears. The engine has a cylinder bore of 3.35" (85 mm), piston stroke of 3.23" (82 mm), and rated power of 51 hp (38 kW). The maximum travel speed (forward/reverse): 15.7 mph (25.3 kph) and 6.6 mph (10.6 kph).

The open center hydraulic system has a gear pump with a rated capacity of 9.3 gal/min (35 l/min). The hydraulic pressure is 181 bar (2630 psi). The 2-wheel drive models are equipped with 6.0x16 front tires and 14.9x28 rear tires. The 8.3x24 front tires and 14.9x28 rear tires are used for 4-wheel drive tractors. The Kubota M4950 tractor can be equipped with Kubota M1840A front-end loader with a lift capacity to full height of 2350 lbs (1065 kg) and breakout force of 4400 (1995 kg).

Engine Troubleshooting
Engine doesn't start or difficult to start
Fuel filter clogging - Clean the filter or install new filter element
The fuel shut-off valve is closed - Open fuel shut-off valve
Air trapped in fuel system - Bleed air
Dirty or damaged injectors - Inspect fuel injectors and replace if necessary
Faulty fuel injection pump - Change pump or rebuild it
Bad engine compression - Check and change damaged parts
Engine stops running unexpectedly
Engine not warmed up - Warm up the engine
Air in fuel system - Air-bleed fuel system
Uneven fuel injections - Repair or adjustment
Fuel filter is dirty - Clean the filter element
Dirty or damaged injectors - Change fuel injectors
Diesel starts but suddenly stops
Incorrectly set fuel injection pump timing - Fuel pump timing settings need to be corrected
Fuel filter is dirty - Clean or replace the filter
Fuel injector nozzles are damaged - Test injector nozzles and replace as required
Fuel injection pump is broken - Replace injection pump or repair it
Dirty air cleaner element - Install new cleaner element or replace it
Engine stalls when idling
Low idle speed set incorrectly - Need to adjust idle speed
Fuel injection pump is defective - Replacement or repair required
Fuel injector nozzles are defective or dirty - Test injector nozzles and replace as required
Incorrect valve clearance - Adjust valve clearance
Engine overheating
Coolant level is low - Fill radiator to proper level. Check and repair damage to the cooling system if required
Cooling system parts are damaged or system is dirty - Replace faulty parts or flush the cooling system
Engine oil level is low - Fill up the engine oil
Incorrect fan belt tension or broken belt - Adjust as required or change belt
Thermostat is defective - Check thermostat, replace if necessary
Diesel power loss
Dirty or faulty injectors - Inspect fuel injectors and replace if necessary
Fuel injection pressure is wrong - Test fuel injection pressure and adjust it correctly
Clogged air filter element - Change or replace air filter element
Clogged oil filter - Service or change engine oil filter element
Engine overload - Reduce engine load
Valve clearance is wrong - Adjust valve clearance
Incorrectly adjusted low idle speed - Correct the settings
Dirty fuel hoses or pipes - Clean fuel system pipes and hoses
Engine losing compression: Valves are damaged or leaking - Change the valves
Engine knocking sound or abnormal noise
Incorrectly set fuel injection pump timing - Fuel injection pump timing adjustment needs to be corrected
Fuel injector nozzles fault - Install a new set of well-balanced nozzles
Engine oil insufficient - Check oil level and add oil as required
Engine is not warmed up to required temperature - Normalize the engine temperature
Main bearings or crankshaft wear - Worn parts replacement required
Damaged or defective piston rings - Piston rings replacement required
Loose flywheel bolts - Check flywheel bolts and tighten properly
Diesel engine consuming too much oil
Oil leaking: Gaskets or seals can be faulty - Change to repair leaks
Improper oil viscosity - Use correct viscosity oil
Stuck or worn piston rings - Piston rings need to be replaced
Valve stems and guides are worn - Change the valves
Worn cylinder liners or pistons - Inspect pistons and liners, change as required

Electrical System Troubleshooting
Battery will not charge
Battery dead cell - Change the battery
Bad battery electrical wire harness - Check wires for malfunctions, repair or replace
Loose or corroded battery cables and terminals - Terminals and cables need to be tightened or cleaned
Belt is defective or belt tension is improperly adjusted Adjust belt tension as required or replace belt
Starter cranks slowly
Battery power is low - Battery is drained, charge it
Battery won’t hold charge - Battery needs to be serviced or replaced
Bad battery wiring harness - Inspect wiring for malfunctions, replace or repair
Battery terminals and cables are loose or corroded - Tighten or clean cables and terminals
Starter will not crank
Low battery power - Recharge the battery
Discharged or worn battery - Need to charge or replace the battery
Damaged starter motor - Replace or repair starter
Battery cables are disconnected or incorrectly connected - Check cables and reconnect it correctly

Transmission Troubleshooting
Hard shifting
Clutch is not adjusted or faulty - Clutch adjustment or replacement required
Loose or broken gear shift linkage - Replace or repair the shift linkage
Bent or worn shift forks - Change the shift forks
Defective gearshift mechanism - Replace defective components
Insufficient transmission fluid pressure
Not enough fluid in transmission - Check transmission fluid level and add it as required
Transmission oil filter clogging (if fitted) - Change or clean the transmission oil filter
Relief valve sticking - Replace the valve
Transmission is excessively noisy
Cracked or worn bearings - Faulty bearings should be changed
Lack of transmission fluid supply - Fill up the transmission fluid
Dirty transmission oil - Transmission oil must be changed
Damaged gears or improper backlash - Replace gears or set backlash correctly
Worn or damaged shift forks - Replace defective shift forks
Transmission oil leaking
Seals or gaskets are damaged - Gaskets or seal replacement required
Cracked transmission housing - Housing needs to be replaced

Hydraulics Troubleshooting
Excessive hydraulic system heat
Hydraulic system pressure is not set correctly - Set the hydraulic pressure as required
Main relief valve malfunction or incorrect adjustment - Adjust relief valve or change if required
Hydraulic oil is contaminated - Fill up with fresh hydraulic oil
Air in hydraulic system - Inspect the pump seals, suction line, and fittings
Hydraulic oil pressure is low
Hydraulic oil level is low - Fill up the hydraulic oil
Hydraulic oil filter clogging - Clean the hydraulic filter element or replace if necessary
Faulty hydraulic oil pump - Test the pump performance and change pump if required
Hydraulic spool valve block is defective or set improper - Set properly or replace
Hydraulic cylinder malfunction - Inspect cylinder parts for wear or damage and replace if required
Leakage in hydraulic lines - Detect leaks in hydraulic system and repair it
3-point hitch does not raise or raises very slowly
Not enough hydraulic fluid in the system - Add fluid to the hydraulic system
Hydraulic fluid is too cold - Allow fluid to warm
Hydraulic oil filter element clogging - Change hydraulic filter element or clean if necessary
Hydraulic pump failure - Check pump flow and install new pump if necessary
Main relief valve failure or incorrect setting - Adjust relief valve or change if required
Hydraulic control valve block is not set properly or defective - Change or adjust correctly
Defective hydraulic cylinder - Inspect the hydraulic cylinder parts for damage or wear and replace if required
Broken or disconnected suction line - Connect or replace
3-point hitch fails to drop or drops slowly
Hydraulic control valve block is defective or set improper - Change or adjust properly
Hydraulic cylinder is broken - Check the hydraulic cylinder parts for damage or wear and replace if necessary
Damaged hitch rock shaft - Install a new shaft
Mechanical parts of the hitch are damaged - Change worn or damaged hitch components
Jerky lifting or lowering of 3-point hitch
Aeration in hydraulic system - Inspect the pump seals, suction line, and fittings
Contaminated hydraulic oil - Change hydraulic oil
Damaged hydraulic oil pump - Check pump flow and change pump if necessary
Faulty or incorrect setting hydraulic spool valve - Adjust properly or change
Hydraulic cylinder malfunction - Inspect cylinder parts for wear or damage and replace if required



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