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Bobcat A770 Troubleshooting

The Bobcat A770 skid steer loader driveline system components: a 230 cu.in (3.8L) Kubota V3800 4-cylinder turbocharged diesel engine with a rated power of 92 hp (68.6 kW), and 2-speed transmission. The hydraulic system has a pump with a rated capacity of 23 gal/min (87.1 l/min). The system relief pressure is 3550 psi (245 bar). The Bobcat A770 is equipped with a vertical-lift loader boom, all-wheel steering, 120 HSOC roller chains, and 12x16.5 or 33-15.5x16.5 tires. The skid steer has a boom lifting force of 5365 lbs (2434 kg) and bucket breakout force of 5500 lbs (2495 kg). The rated operating capacity is 3325 lbs (1508 kg), and tipping load is 6650 lbs (3016 kg).

Engine Troubleshooting

Engine starts hard or doesn't start
Air in the fuel system - Air bleeding.
Clogged fuel filter - Clean the filter element.
Faulty or dirty injection nozzles - Inspect nozzles and replace if necessary.
Water in the fuel system - Change fuel and repair fuel system.
Excessive valve clearance - Adjust valve clearance according to specifications.
Faulty fuel injection pump - Repair or install a new fuel pump.

Engine starts but stops suddenly
Dirty air cleaner - Clean or change.
Fuel filter plugged - Change or clean the filter element.
Fuel injection pump has loose connections - Tighten the connections.
Clogged or defective injectors - Test and replace fuel injectors if necessary.
Fuel injection pump is not working correctly - Repair or change injection pump.

Engine stops suddenly during operation
Engine is not preheated - Warm up engine as required.
Fuel filter plugging - Service or replace the filter.
Air in the fuel lines - Bleed the fuel lines.
Faulty or dirty injection nozzles - Test injection nozzles and change if necessary.
Incorrect adjustment of fuel injection pump timing - Check the fuel injection pump timing adjustment.

Engine stalls while idle
Low idle speed setting is incorrect - Adjust low idling as recommended.
Damaged fuel injection pump - Install a new fuel pump or repair.
Clogged or defective injectors - Replace or clean fuel injectors.
Valve clearance is out of adjustment - Need to adjust valve clearance.

Engine loses power
Dirty air cleaner - Clean or change.
Fuel injection nozzles are faulty or clogged - Clean or change injection nozzles.
Improper fuel injection pressure - Test fuel injection pressure and adjust it correctly.
Valve clearance is not correct - Check and adjust as required.
Incorrect low idle speed adjustment - Test and adjust.
Clogged fuel hoses or lines - Service fuel lines and hoses.
Cylinder-head gasket is broken - Cylinder-head gasket replacement required.
Defective or worn piston rings - Replace piston rings.

Engine is overheated
Coolant level is low - The cooling system needs to be refilled and checked for faults.
Engine oil insufficient - Check and refill engine oil.
Dirty radiator core or faulty radiator cap - Clean radiator or replace cap.
Broken or loose fan belt - Belt replacement is recommended.
Engine overloaded - Reduce load on the engine.

Insufficient oil pressure
Oil level is low - Check and refill the oil.
Clogged oil filter element - Replace or service engine oil filter.
Incorrect engine oil Use oil of correct viscosity.
Crankshaft bearing has excessive oil clearance - Change bearings.
Oil pump failure - Remove and inspect oil pump.

Engine noises or knocks
Low engine oil level - Need to add engine oil.
Low coolant temperature - Warm up the engine.
Timing of fuel injection pump is incorrect - Set up as recommended.
Too low idle RPM - Adjust low idling as recommended.
Damaged or clogged injectors - Inspect fuel injectors and change as required.
Connecting rod is defective or not aligned - Need to align or replace the connecting rod.
Worn or scored pistons - Install new pistons.

Drive System Troubleshooting

Machine will not move in either direction or one direction
Hydraulic oil level is low - Checking hydraulic oil level and add if necessary.
Drive chain is worn - Check drive chain and change faulty components.
Input drive shaft malfunction - Change or repair.
Relief valve is stuck - Repair or replace relief valve.
Plugged suction line or hydraulic filter - Clean suction line or replace hydraulic filter.
Defective foot or hand controls - Replace or repair.
Drive pump or motor malfunction - Inspect and replace as necessary.

Reduced power
Dirty hydraulic oil filter - Check, clean, or replace as required.
Relief valve is opened or defective - Close or change relief valve.
Transmission parts are faulty or damaged - Check and replace defective components.
Stuck input drive shaft - Change or repair faulty drive shaft.
Air in hydraulic system - Air bleeding is required.

Drive system is overheated
Hydraulic oil is insufficient - Need to add oil.
Plugged hydraulic fluid filter - Replace or service hydraulic filter.
Relief valve defective or worn - Service or change relief valve.
Drive pump or hydraulic motor is damaged - Check and repair if required.
Hydraulic oil cooler is plugged - Clean cooling fins as required.
Transmission overloading - Reduce the load.

Excessive noise
Oil viscosity is wrong - Drain and refill with correct oil.
Air in hydraulic system - Bleed air from system.
Hydraulic motor or drive pump is worn - Inspect and replace as necessary.
Mechanical parts of drive system are damaged or worn - Inspect drive system and replace faulty components.

Hydraulics Troubleshooting

Hydraulic system overheated
Incorrect hydraulic pressure setting - Correct setting is required.
Main relief valve is damaged or adjusted improperly - Adjust the valve or replace if necessary.
Hydraulic fluid is contaminated - The fluid must be changed.
Lack of hydraulic oil - Fill up the hydraulic oil.
Worn hydraulic oil pump - Install new pump or repair it.

Boom can't lift or drop
Lift controls failure - Change or repair.
Hydraulic pump failure - Repair or replace pump if necessary.
Faulty hydraulic control valve - Install a new hydraulic valve or repair it.
Hydraulic cylinder is defective - Change or repair lift cylinder.
Hydraulic oil is insufficient - Checking hydraulic oil level and add if necessary.

Bucket can't tilt
Faulty bucket tilt controls - Inspect and repair if necessary.
Hydraulic pump failure - Repair or change pump if required.
Defective hydraulic control valve - Change or repair hydraulic valve.
Bucket cylinder malfunction - Replace or repair cylinder.
Hydraulic oil is insufficient - Fill the system to proper hydraulic oil level.

Slow boom or bucket operation
Faulty hydraulic oil pump - Test pump flow rate and replace pump if required.
Hydraulic cylinder leaking - Change cylinder piston seals.
Low hydraulic fluid level - Fill up the hydraulic fluid.
Worn or unadjusted hydraulic control valve - Repair or adjust correctly.
Hydraulic system loosing pressure - Hydraulic pressure must be set correctly.

Lift arm or bucket is jerky
There is air in the hydraulic system - Air bleeding is required.
Hydraulic oil filter element clogging - Service or replace the hydraulic filter.
Dirty hydraulic fluid - The fluid must be changed.
Scratched cylinder rod or tube - Replace worn component.

Hydraulic pump is excessively noisy
Hydraulic leaks or low oil level - Add hydraulic oil or correct system leaks.
Hydraulic filter is dirty - Clean or replace the filter.
Dirty suction line - Need to service the suction line.
Pump is sucking air - Bleed air.
Pump parts are damaged - Install new hydraulic pump or rebuild it.

Electrical Troubleshooting

Battery won’t charge
Loose or corroded electrical wiring connections - Tighten or service cable connections.
Faulty battery terminal clamps - Terminal clamps need to be replaced.
Worn-out battery - Battery replacement required.
Loose or worn belt - Adjust belt tension or change the belt.

Starter turns slowly
Low battery power - Battery needs to be recharged.
Battery runs out quickly - Service charging system or install new battery.
Disconnected wires or corroded battery terminals - Check wire connections and change or service terminals.

Starter is not cranking
Battery is drained or worn - Recharge or replace battery.
Wiring is improperly connected or disconnected - Check wiring and connect properly.
Battery voltage is low - Battery is drained, recharge it.
Starter motor failing - Replace or repair starter.