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Bobcat S750 Troubleshooting

The Bobcat S750 skid steer loader is powered by Kubota V3800 diesel engine with a rated power of 85 hp (63 kW) or Bobcat Doosan D34 diesel engine with a rated power of 85 hp (63 kW). The Bobcat S750 is equipped with one-speed or two-speed hydrostatic transmission, vertical-lift loader boom, 120 HSOC roller chains, and 12x16.5 or 33-15.5x16.5 tires. The hydraulic system has a pump with fluid flow rate of 23 gpm (87.1 lpm). The hydraulic pressure is 3500 psi (241 bar). The skid steer loader has a rated operating capacity of 3200 lbs (1452 kg) and tipping load of 6400 lbs (2905 kg). The lift height is 132" (3355 mm) to hinge pin, and dump height is 104.3" (2650 mm).

Engine Troubleshooting

Engine starts up hard or won't start
Air trapped in fuel system - Bleed air.
Clogged fuel filter - Change filter element.
Dirty or damaged injection nozzles - Service or change injection nozzles.
Water in the fuel system - Change fuel and repair fuel system.
Excessive valve clearance - Need to adjust valve clearance.
Fuel injection pump is defective - Change or repair the pump.

Diesel starts but immediately stops
Air filter is clogged - Clean or replace element.
Clogged fuel filter - Change or clean the filter element.
Fuel injection pump has loose connections - Tighten the connections.
Fuel injectors are faulty or clogged - Test and replace fuel injectors if necessary.
Defective fuel injection pump - Rebuild or install a new injection pump.

Engine stalls while running
Engine is not fully warmed up - Warm up engine as required.
Clogged fuel filter - Replace filter element.
Air in fuel system - Bleed fuel system.
Faulty or dirty injection nozzles - Install a new kit of correctly balanced nozzles.
Improper fuel injection timing - Set the fuel pump timing correctly.

Engine stalls at idle
Improperly adjusted low idle speed - Adjust as required.
Fuel injection pump failure - Repair or change injection pump.
Fuel injectors are faulty or clogged - Clean or replace fuel injectors.
Excessive valve clearance - Have it adjusted.

Diesel engine is losing power
Air filter is dirty - Replace or clean air filter element.
Clogged or burnt injection nozzle - Change fuel injection nozzles.
Insufficient fuel injection pressure - Test fuel injection pressure and adjust it correctly.
Valve clearance is wrong - Correct valve clearance needs to be set.
Wrong adjustment of low idle speed - Test and adjust.
Dirty fuel hoses or lines - Service fuel lines and hoses.
Blown cylinder head gasket - Cylinder-head gasket replacement required.
Piston rings are worn or defective - Replace the piston rings as required.

Engine is overheated
Lack of engine coolant - Fill radiator to proper level and check components for faults.
Low engine oil level - Check and refill engine oil.
Radiator core is dirty or radiator cap is damaged - Clean radiator or replace cap.
Loose or damaged fan belt - Belt change is required.
Diesel engine is overloaded - Reduce load on the engine.

Oil pressure is insufficient
Lack of oil - Fill up the engine oil.
Oil filter element is dirty - Replace or service engine oil filter.
Wrong oil viscosity - Drain and refill with oil of correct grade and viscosity.
Crankshaft bearing has incorrect oil clearance - Bearing needs to be changed.
Oil pump is defective - Repair or change.

Engine knocking or noise
Engine oil level low - Fill the crankcase with engine oil.
Engine not warmed up - Warm up the engine.
Incorrect adjustment of fuel injection pump timing - Adjust fuel injection pump as required.
Incorrectly adjusted low idle speed - Correct low idle settings.
Damaged or clogged injectors - Inspect fuel injectors and change as required.
Connecting rod misalignment or failure - Connecting rod needs to be aligned or changed.
Scored or worn pistons - Replace the pistons.

Drive System Troubleshooting

Machine is not moving forward or backward
Hydraulic oil level is low - Check and refill the hydraulic oil.
Drive chain failure - Check drive chain and change defective components.
Damaged input drive shaft - Service or change drive shaft.
Relief valver is broken - Repair or install a new relief valve.
Hydraulic filter or suction line is plugged - Clean suction line or replace hydraulic filter.
Worn or damaged foot or hand controls - Repair or replace.
Drive motor or pump failure - Inspect and replace as necessary.

Lack of power
Hydraulic oil filter is clogged - Replace hydraulic filter.
Damaged or opened relief valve - Change or close relief valve.
Faulty or worn transmission components - Check and change faulty components.
Worn input drive shaft - Repair or replace drive shaft.
Air in hydraulic system - Need to bleed air.

Drive system overheats
Insufficient hydraulic oil - Fill the system to proper hydraulic oil level.
Clogged hydraulic fluid filter - Change or service hydraulic filter.
Defective or worn relief valve - Repair or replace.
Hydraulic motor or drive pump is defective - Repair or replace faulty component.
Clogged hydraulic oil cooler - Clean cooling fins as required.
Drive system overload - Load needs to be reduced.

Excessive noise
Oil viscosity is too heavy - Drain and refill with proper oil.
There is air in the hydraulic system - Bleed hydraulic system.
Hydraulic motor or drive pump is defective - Change or repair faulty component.
Worn or damaged mechanical parts of drive system - Inspect the parts for defect or damage and repair as required.

Hydraulics Troubleshooting

Hydraulic system overheats
Hydraulic pressure is not correct - Adjust it correctly.
Main relief valve is damaged or adjusted improperly - Adjust the valve or replace if necessary.
Dirty hydraulic fluid - Fill up with fresh hydraulic fluid.
Hydraulic fluid level is low - Add fluid to the hydraulic system.
Hydraulic pump is faulty - Replace or repair pump if necessary.

Boom fails to lift or drop
Defective lift controls - Repair or change.
Defective hydraulic pump - Repair or replace pump if necessary.
Faulty hydraulic control valve - Install a new valve or repair it.
Broken hydraulic cylinder - Install a new boom cylinder or repair it.
Low hydraulic oil level - Fill the system to proper hydraulic oil level.

Bucket is not working
Bucket controls failure - Change or repair.
Hydraulic pump not working - Repair or replace pump if necessary.
Defective hydraulic control valve - Install a new valve or repair it.
Bucket cylinder malfunction - Repair or replace cylinder.
Hydraulic fluid is insufficient - Fill up the hydraulic fluid.

Slow bucket or lift arm operation
Faulty hydraulic oil pump - Check pump capacity and change if necessary.
Oil leaks from hydraulic cylinder - Cylinder seals need to be replaced.
Hydraulic oil is insufficient - Need to add oil.
Damaged or incorrect adjusted hydraulic control valve - Set correctly or repair.
Hydraulic pressure is low - Adjust pressure correctly.

Bucket or boom jerks when working
There is air in the hydraulic system - Bleed hydraulic system.
Hydraulic oil filter is dirty - Service or replace the hydraulic filter.
Contaminated hydraulic fluid - Change hydraulic fluid.
Cylinder tube or rod is scored - Replace damaged component.

Excessive hydraulic pump noise
Hydraulic leaks or lack of oil - Top up hydraulic oil or remedy leakage in system.
Hydraulic filter is clogged - Replace or clean the filter.
Plugged suction line - Need to service the suction line.
Pump is sucking air - Remove air from hydraulics.
Worn pump parts - Change or rebuild pump.

Electrical Troubleshooting

Battery does not charge
Wiring connections are corroded or loose - Service or tighten connections.
Battery terminal clamps are faulty - Install new terminal clamps.
Bad cell in battery - Replace the battery.
Loose or worn belt - Adjust belt tension or change the belt.

Starter cranks slow
Low battery output voltage - Battery is drained, recharge it.
Battery won’t hold charge - Service battery or replace it.
Faulty battery terminals or disconnected cables - Check wiring connections and replace or clean terminals.

Starter motor is not working
Battery is low or faulty - Battery needs to be recharged or replaced.
Wiring is incorrectly connected or disconnected - Inspect wiring and connect correctly.
Low battery voltage - Battery is drained, recharge it.
Defective starter motor - Repair or install a new starter.