Gehl 6640 Skid Steer Troubleshooting

The Gehl 6640 skid steer loader driveline system components: a 190 cu.in (3.1L) Deutz BF4M2011 4-cylinder direct injection turbocharged liquid-cooled diesel engine with a rated power of 82 hp (61 kW), and 1-speed or 2-speed hydrostatic transmission. The hydraulic system has a pump with a rated capacity of 23 gal/min (87.1 l/min). The system pressure is 3000 psi (207 bar). The Gehl 6640 is equipped with 100 roller drive chains and 12x16.5-10 or 14x17.5-12 tires. The skid steer loader has a lift height of 123" (3125 mm) to hinge pin and dump height of 91.3" (2320 mm). The rated operating capacity is 2400 lbs (1090 kg), and tipping load is 4800 lbs (2180 kg).

Engine Troubleshooting

Engine starts hard or won't start

Air in the fuel pipes - Bleed the fuel pipes.
Fuel filter element is dirty - Replace the filter element.
Fuel injection nozzles are dirty or defective - Install a new kit of correctly balanced nozzles.
Dirt or water in fuel system - Drain water or flush dirt from the system.
Excessive valve clearance - Adjust valve clearance according to specifications.
Fuel injection pump failure - Replace or rebuild injection pump.

Diesel starts and suddenly stops

Clogged air filter - Replace or clean air filter element.
Clogged fuel filter - Install new filter element.
Problems with fuel injection pump tightness - Inspect fuel injection pump for leaks.
Defective or clogged fuel injectors - Inspect fuel injectors and change as required.
Fuel injection pump failure - Rebuild or change fuel pump.

Engine stalls while running

Engine is cold - Warm up engine as required.
Fuel filter is plugged - Clean or replace the filter.
Air trapped in fuel system - Bleed air.
Damaged or dirty injection nozzles - Replace injection nozzles.
Improper setting of fuel injection pump timing - Adjust as recommended.

Engine stalls at idle

Improperly adjusted low idle speed - Need to adjust idle speed.
Faulty fuel injection pump - Install a new fuel pump or repair.
Defective fuel injectors - Replace or clean fuel injectors.
Valve clearance is not correct - Adjust valve clearance.

Engine lacks power

Dirty air filter - Clean or replace element.
Fuel injection nozzles are damaged or dirty - Check and replace nozzles if required.
Fuel injection pressure is wrong - Check the fuel injection pressure and adjust if necessary.
Improper valve clearance - Adjust valve clearance.
Too low idle RPM - Normalize low idle speed.
Dirt in the fuel lines or hoses - Fuel lines and hoses need to be cleaned.
Worn cylinder head gasket - Gasket should be replaced.
Piston rings are broken or leaking - Replace the piston rings as required.

Engine overheats

Not enough coolant - The cooling system needs to be refilled and checked for faults.
Engine oil insufficient - Checking oil level and add if necessary.
Clogged radiator core or damaged radiator cap - Install new cap or clean radiator.
Loose or damaged fan belt - Replace as required.
Diesel engine overloaded - Reduce load on the engine.

Low oil pressure

Low oil level - Add oil to the engine crankcase.
Oil filter element clogging - Clean or change engine oil filter.
Incorrect engine oil Use oil of proper viscosity.
Crankshaft bearing has incorrect oil clearance - Change bearings.
Defective oil pump - Repair or change.

Engine knocking sound or abnormal noise

Low engine oil level - Fill up the oil to required level.
Engine not warmed up - Warm up engine as required.
Incorrect adjustment of fuel injection pump timing - Adjust as recommended.
Incorrectly set low idle speed - Normalize low idle speed.
Fuel injector fault - Test and replace fuel injectors if necessary.
Faulty or misaligned connecting rod - Align or replace connecting rod.
Pistons are worn or scored - Replace the pistons.

Drive System Troubleshooting

Machine is not moving forward or backward

Insufficient hydraulic fluid - Checking hydraulic fluid level and add if necessary.
Damaged drive chain - Check drive chain and change faulty parts.
Input drive shaft is faulty - Repair or install a new drive shaft.
Worn or damaged relief valve - Repair or replace relief valve.
Hydraulic filter or suction line is clogged - Service suction line or replace hydraulic filter.
Worn or defective hand or foot controls - Replace or repair.
Drive motor or pump is defective - Repair or change faulty component.

Loss of power

Plugged hydraulic oil filter - Replace hydraulic filter.
Relief valve is defective or opened - Close or replace relief valve.
Transmission parts are faulty or damaged - Check and change faulty components.
Input drive shaft failure - Change or repair faulty drive shaft.
Air leaks in hydraulic system - Bleed hydraulic system.

Drive system keeps overheating

Insufficient hydraulic oil - Checking hydraulic oil level and add if necessary.
Hydraulic fluid filter is clogged - Replace hydraulic filter.
Stuck relief valve - Repair or install a new relief valve.
Hydraulic motor or drive pump is worn - Inspect and change as required.
Plugged hydraulic oil cooler - Clean cooling fins as required.
Drive system overloaded continuously - Reduce drive system load.

Drive system makes excessive noise

Improper oil viscosity - Use correct oil viscosity.
Hydraulic system is leaking air - Bleed air from hydraulic system.
Worn hydraulic motor or drive pump - Inspect and replace as necessary.
Worn or defective mechanical components of drive system - Inspect drive system and replace faulty parts.

Hydraulics Troubleshooting

Hydraulic system overheated

Incorrect hydraulic pressure setting - Adjust it correctly.
Main relief valve is damaged or adjusted improperly - Replace or set up the relief valve.
Dirty hydraulic oil - Fill up with fresh hydraulic oil.
Hydraulic oil level is low - Add oil to the hydraulic system.
Faulty hydraulic oil pump - Repair or replace pump if necessary.

Boom does not raise or lower

Defective lift controls - Change or repair.
Damaged hydraulic oil pump - Repair or replace pump if necessary.
Hydraulic control valve is faulty - Repair or change hydraulic valve.
Hydraulic cylinder is broken - Repair or install a new lift cylinder.
Hydraulic oil is insufficient - Fill the system to proper hydraulic oil level.

Bucket won't move

Damaged bucket controls - Inspect and repair if necessary.
Hydraulic pump is broken - Change or repair hydraulic pump if required.
Hydraulic control valve is faulty - Change or repair hydraulic valve.
Defective bucket cylinder - Install a new cylinder or repair it.
Insufficient hydraulic oil - Checking hydraulic oil level and add if necessary.

Boom or bucket is moving slowly

Hydraulic pump is faulty - Test pump flow rate and replace pump if required.
Oil leaks from hydraulic cylinder - Replace cylinder piston seals.
Hydraulic fluid level low - Checking hydraulic fluid level and add if necessary.
Hydraulic control valve is not set properly or defective - Repair or adjust properly.
Hydraulic pressure has dropped - Adjust it correctly.

Bucket or boom jerks when working

There is air in the hydraulic system - Bleed air from hydraulic system.
Dirty hydraulic oil filter element - Replace or clean the filter.
Hydraulic oil is dirty - The oil must be changed.
Cylinder rod or tube is scratched - Replace failed component.

Hydraulic pump makes excessive noise

Leaking hydraulic system or insufficient oil level - Add hydraulic oil or correct system leaks.
Hydraulic filter is clogged - Clean or replace the filter.
Suction line is dirty - Need to service the suction line.
Air enters the pump - Bleed air from hydraulics.
Pump parts are faulty - Change or rebuild pump.

Electrical Troubleshooting

Battery is not charging

Wiring connections are loose or corroded - Clean or tighten wiring connections.
Battery terminal connectors are defective - Terminal connectors should be replaced.
Battery is worn - Replace the battery.
Worn or loose belt - Adjust belt tension or install a new belt.

Starter turns slowly

Low battery voltage - Charge the battery.
Battery discharges quickly - Service battery or replace it.
Disconnected battery cables or bad terminals - Connect wiring correctly or install new terminals.

Starter motor won't turn

Battery is discharged or defective - Recharge or replace battery.
Wiring is incorrectly connected or disconnected - Inspect wiring and connect correctly.
Battery power is low - Low battery charging, charge as required.
Starter motor failure - Starter needs to be changed.