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Home / Wheel Loaders / Case Wheel Loaders / Case 621B

Case 621B Troubleshooting

The Case 621B wheel loader is powered by 359 cu.in (5.9L) Case 6T-590 4-cylinder turbocharged diesel engine with a rated power of 126 hp (93.9 kW) at 2200 rpm. The Case 621B is equipped with a 4x3 full powershift transmission, power steering system, hydraulic wet disc brakes, and 20.5x25 standard tires. The hydraulic system has a pump with fluid flow rate of 56.4 gpm (213 lpm). The hydraulic pressure is 2250 psi (155 bar). The wheel loader has a rated operating capacity of 8700 lbs (3945 kg) and tipping load of 17400 lbs (7890 kg). The maximum lift height is 144.9" (3680 mm) to hinge pin, and bucket breakout force is 24800 lbs (11250 kg).

Engine Troubleshooting

Engine starts hard or doesn't start
Air in fuel system - Bleed fuel system.
Clogged fuel filter - Clean or change the filter.
Clogged or defective injection nozzles - Check and replace nozzles if required.
Water in the fuel system - Change fuel and repair fuel system.
The valve clearance is not adjusted - Adjustment procedure required.
Fuel injection pump failure - Replace injection pump or repair it.

Diesel starts and stalls immediately
Clogged air filter - Service or replace the air filter.
Fuel filter element is clogged - Clean or change the filter.
Poor fuel injection pump tightness - Look for any leaks of fuel pump, tighten it fast.
Fuel injectors are faulty or clogged - Inspect fuel injectors and change as required.
Fuel injection pump is faulty - Replacement or repair required.

Engine shuts off suddenly during operation
Engine is not fully warmed up - Warm up to required temperature.
Fuel filter element clogging - Clean or replace the filter.
There is air in the fuel system - Bleed the system.
Fuel injection nozzles fault - Check and replace nozzles if required.
Fuel injection pump timing is not adjusted - Adjust as recommended.

Engine stalls while idling
Low idle speed set incorrectly - Correct low idle settings.
Fuel injection pump damage - Replacement or repair required.
Damaged or clogged injectors - Replace fuel injectors.
The valve clearance is incorrect - Adjust valve clearance according to specifications.

Loss of engine power
Dirty air filter - Service or replace the air filter.
Clogged injection nozzle - Replace injection nozzles.
Fuel injection pressure is wrong - Adjust pressure to proper level.
Valve out of adjustment - Adjust valve clearance.
Low idle speed set incorrectly - Correct low idle adjustment.
Fuel hoses or lines clogging - Fuel hoses and lines must be clean.
Damaged cylinder-head gasket - Cylinder-head gasket replacement required.
Piston rings are broken or leaking - Change piston rings.

Engine overheats
Low coolant level - Top up coolant fluid and check system for leaks.
Engine oil level is low - Check and refill engine oil.
Dirty radiator fins or defective radiator cap - Clean radiator or replace cap.
Fan belt is loose or defective - Belt replacement is recommended.
Engine is under excessive load - Load reducing required.

Low oil pressure
Low oil level - Checking oil level and add if necessary.
Clogged oil filter - Replace or service engine oil filter.
Oil grade or viscosity is incorrect - Use correct viscosity oil.
Excessive main bearing oil clearance - Bearing needs to be changed.
Defective oil pump - Replace as required.

Engine knocking or noise
Insufficient engine oil - Fill up the oil to required level.
Engine is cold - Warm up the engine.
Improper setting of fuel injection pump timing - Check the fuel injection pump timing adjustment.
Low idle speed setting is not correct - Need to adjust idle speed.
Fuel injectors are dirty or defective - Clean fuel injectors or change it.
Misaligned or faulty connecting rod - Replace or align connecting rod.
Pistons are worn or broken - Pistons replacement required.

Transmission Troubleshooting

Low transmission pressure
Low fluid level - Need to add transmission fluid.
Transmission fluid filter element clogging (if equipped) - Service or replace the transmission fluid filter.
Relief valve is damaged - Replace the valve.

Transmission noises
Lack of transmission fluid - Need to add transmission fluid.
Transmission fluid is contaminated - Fill up with fresh transmission fluid.
Defective gears or improper backlash - Install new gears and adjust backlash properly.
Worn or cracked bearings - Change faulty bearings.
Shift forks are bent or worn out - Replace the shift forks.
Shaft splines are stuck or worn out - Replace defective shaft.

Gear hard to shift
Worn or rusty gear shift linkage - Install a new gear shift linkage.
Damaged or worn gear shift forks - Shift forks need to be changed.
Defective parts in the gearshift mechanism - Replace defective parts.
Improperly adjusted or worn clutch - Clutch needs to be replaced or adjusted.

Transmission fluid leaks
Too much oil in transmission - Drain the excess oil.
Seals or gaskets are worn - Install new components.

Hydraulics Troubleshooting

Hydraulic system overheated
Hydraulic pressure incorrectly adjusted - Correct adjustment is required.
Defective or misadjusted main relief valve - Replace or set up the relief valve.
Hydraulic fluid contamination - Hydraulic fluid change required.
Lack of hydraulic oil - Fill up the hydraulic oil.
Faulty hydraulic oil pump - Repair or install new hydraulic pump.

Boom cannot be lowered or raised
Lift controls failure - Replace or repair.
Hydraulic pump failure - Repair or replace pump if necessary.
Hydraulic control valve is faulty - Repair or change the valve.
Hydraulic cylinder malfunction - Repair or change hydraulic cylinder.
Low hydraulic fluid level - Fill up the hydraulic fluid.

Bucket does not tilt
Damaged bucket controls - Check and repair as required.
Damaged hydraulic oil pump - Repair or change pump if required.
Faulty hydraulic control valve - Repair or replace the valve.
Hydraulic bucket cylinder is defective - Repair or install a new cylinder.
Hydraulic oil level low - Checking hydraulic oil level and add if necessary.

Bucket or lift arm is working slowly
Hydraulic pump is defective - Test the pump flow rate and install new pump if required.
Leaking hydraulic cylinder - Cylinder seals need to be replaced.
Low hydraulic fluid level - Fill the system to proper hydraulic fluid level.
Worn or unadjusted hydraulic control valve - Repair or set properly.
Hydraulic pressure has dropped - Correct setting is required.

Jerky operation of the bucket or boom
Air in hydraulic system - Bleed hydraulic system.
Dirty hydraulic oil filter element - Clean or change the filter.
Dirty hydraulic fluid - Fill up with fresh hydraulic fluid.
Cylinder rod or tube is scratched - Change worn component.

Hydraulic pump is noisy
Insufficient oil level or leaking hydraulic system - Remedy hydraulic leakage or refill oil as necessary.
Plugged hydraulic filter - Service or replace hydraulic filter.
Suction line is dirty - Need to service the suction line.
Air in hydraulic pump - Bleed air from hydraulics.
Pump parts are damaged - Rebuild or change hydraulic pump.

Electrical Troubleshooting

Battery will not charge
Wiring connections are loose or corroded - Tighten or service connections.
Defective battery terminal clamps - Replace terminal clamps.
Bad cell in battery - Change the battery.
Defective or loose belt - Adjust belt tension or install a new belt.

Starter turning slow
Battery capacity is low - Low battery charging, charge as required.
Battery runs out quickly - Service battery or change it.
Disconnected wiring or bad battery terminals - Connect cables properly or replace terminals.

Starter doesn't crank
Battery is drained or worn - Charge or replace the battery.
Wiring harness is disconnected or improperly connected - Check wiring harness and connect as required.
Low battery output voltage - Battery needs to be recharged.
Starter motor failing - Starter needs to be replaced.

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WHEEL LOADERS SPECIFICATIONS

Wheel Loaders, Skid Steers, and Compact Track Loaders