Introduction

NOTE: For Specifications with illustrations, make reference to the SPECIFICATIONS for 910 LOADER HYDRAULIC SYSTEM, Form No. SENR7220. If the Specifications given in Form SENR7220 are not the same as listed in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications listed in the book with the latest date.

Problem Solving

Hydraulic oil, under pressures that can be higher than 3000 psi (20 700 kPa) can remain in the hydraulic systems on this machine after the engine and pump have been stopped. Serious injury can be caused if this pressure is not released before any service is done on the hydraulic systems. To prevent possible injury, be sure that the pressure is released before any fitting, hose or component is loosened, tightened, removed or adjusted.

When possible, the bucket must always be flat on the ground before service is started. When it is necessary for the bucket to be raised while tests or adjustments are done, be sure that the lift arms have correct support and the bucket is in the full dump position.

Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.

The 5S5123 Hydraulic Testing Group is used to make the pressure tests of the hydraulic system. Before making any test, visually inspect the complete hydraulic system by looking for leakage of oil and for parts that have damage. For some of the tests a magnet and a measuring rule (either for inches or millimeters) are usable tools.

Visual Checks

A visual inspection of the hydraulic system and its components is the first step when making a diagnosis of a problem. Stop the engine and lower the bucket to the ground. When the oil is cool so any pressure in the tank will be at a minimum, make the following inspections:

1. Measure the oil level. Slowly turn the filler cap until it is loose. If oil comes out the bleed hole when the filler cap is turned, let the tank pressure lower before removing the filler cap. Look for air in the oil in the tank.

2. Remove the filter element and look for particles removed from the oil by the filter element. A magnet will separate ferrous particles from non-ferrous particles (piston rings, O-ring seals, etc.).

3. Check all oil lines and connections for damage or leaks.

Performance Test List

Performance tests of the hydraulic system can be used for a diagnosis of poor performance and to find the source of oil leakage inside the hydraulic system.

PROBLEM: Pump makes noise, the cylinder rods do not move smoothly and there are air bubbles in the oil.

PROBABLE CAUSE:

1. The viscosity of the oil is wrong.

2. The relief valve opens at low oil pressure.

3. Loose connection of the oil line on the inlet side of the pump.

4. The pump has too much wear.

PROBLEM: The temperature of the oil is too hot.

PROBABLE CAUSE:

1. The viscosity of the oil is wrong.

2. The relief valve opens at low oil pressure.

3. The pump has too much wear.

4. There is a restriction in an oil passage.

5. The load of the system is too high.

PROBLEM: The output of the pump is low.

PROBABLE CAUSE:

1. Low level of the oil in the tank.

2. The viscosity of the oil is wrong.

3. The pump has too much wear.

PROBLEM: The pressure of the oil is low.

PROBABLE CAUSE:

1. The relief valve opens at low oil pressure.

2. The pump has too much wear.

3. The failure of an O-ring seal in the system.

PROBLEM: The lift and tilt cylinders move too slow.

PROBABLE CAUSE:

1. The pressure of the oil is low.

2. The output of the pump is low.

3. The failure of a seal on a piston in a cylinder.

PROBLEM: Bucket moves with control lever in HOLD POSITION.

PROBABLE CAUSE:

1. The control valve and valve spool have a large amount of wear.

2. A piston seal in a cylinder has a large amount of wear.

3. A leak in a connection between the control valve and the cylinders.

Checking Pump Efficiency

For any pump test at a given rpm, the pump flow (gpm) at 100 psi (690 kPa) will be larger than the pump flow (gpm) at 1000 psi (6900 kPa).

The difference between the pump flow of two operating pressures is the flow loss.

Flow loss when expressed as a percent of flow loss is used as a measure of pump performance.

If the percent of flow loss is more than 10% for test on the machine or 15% for test on the bench, pump performance is not good enough.

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^*Numbers in examples are for illustration and are not values for any specific pump or pump condition. See LOADER HYDRAULIC SYSTEM SPECIFICATIONS, Form No. SENR7220 for pump flow of a new pump at 100 psi and 1000 psi.

Test On The Machine

Install a 9S2000 Flow Meter. Measure pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa) with engine at 2000 rpm.

NOTE: See Tee Test Tooling Chart, Form Number REG00910.

Test On The Bench

If the test bench can not be run at 1000 psi at a high rpm, do the first part of the test with the pump shaft rotation at 1100 rpm. Measure pump flow at 100 psi (690 kPa) and at 1000 psi (6900 kPa). Then in order to measure the pump flow for the last part of the test, see LOADER HYDRAULIC SYSTEM SPECIFICATIONS, Form No. SENR7220, for: Pump rpm at 100 psi with the engine at 2000 rpm.

Test For Drift Of Cylinder Rods

Lift Cylinders

Drift measurements are the maximum permissible during the time interval shown for the oil temperature in the system.

Start the engine. Move the control lever to the RAISE position until the bucket is fully lifted. Then, hold the lever in RAISE position for five seconds. Lower the bucket. Do this lift and lower cycle many times to increase the temperature of the hydraulic oil.

TEST NO. 1: Move the control lever to the LOWER position. Hold the lever until the front of the machine is lifted off the ground. Move the control lever to the HOLD position and stop the engine. Look at the hydraulic cylinder to see if there is a drift of the cylinder rod.

The drift of the cylinder rod is caused by:

1. Leakage of oil around the valve spool in the control valve.

2. The make-up valve for the circuit for the rod end of the cylinder is not closed.

TEST NO. 2: Move the control lever to the LOWER position. Hold the lever until the front of the machine is lifted off the ground. Stop the engine. Hold the control lever in the LOWER position and look at the hydraulic cylinder to see if there is a drift of the cylinder rod.

The drift of the cylinder rod is caused by:

1. Leakage of oil around valve spool in control valve.

2. The make-up valve in the circuit for the rod end of the cylinder is not closed.

3. The check valve in the control valve is not closed.

TEST NO. 3: With bucket empty, move the control lever to the RAISE position until the bucket is fully lifted. Move the control lever to the HOLD position and stop the engine. Look at the hydraulic cylinder to see if there is a drift of the cylinder rod.

The drift of the cylinder rod is caused by:

1. Leakage of the oil around the valve spool in the control valve.

2. Leakage of the oil in the head end of the cylinder around the seal on the piston into the rod end of the cylinder.

TEST NO. 4: With bucket empty, move the control lever to the RAISE position, until the bucket is fully lifted. Stop the engine and hold the lever in the RAISE position. Look at the hydraulic cylinder to see if there is a drift of the cylinder rod.

The drift of the cylinder rod is caused by:

1. Leakage of the oil around the valve spool in the control valve.

2. The check valve in the control valve is not closed.

3. Leakage of the oil in the head end of the cylinder around the seal on the piston into the rod end of the cylinder.

Tilt Cylinders

Drift measurements are the maximum permissible during the time interval shown for the oil temperature in the system.

TEST NO. 1: With the engine running and with the bucket on the ground in digging position, move the control lever to the DUMP position. After the bucket lifts the front wheels of the machine, move the control lever to the HOLD position and stop the engine. Look at the hydraulic cylinders to see if the rods drift into the cylinders.

The drift of the cylinder rods is caused by:

1. Leakage around the valve spool in the control valve.

2. Relief valve in the circuit to the head ends of the cylinders is either leaking or is damaged.

3. Leakage of the oil in the head ends of the cylinders around the seals on the pistons into the rod ends of the cylinders.

TEST NO. 2: Hold the control lever in the DUMP position and look at the hydraulic cylinders to see if the cylinder rods drift.

NOTE: It may be necessary to start the engine and lift front wheels of the machine by moving the control lever to the DUMP position. The engine must be stopped when making the test.

The drift of the cylinder rods is caused by:

1. Leakage around the valve spool in the control valve.

2. Relief valve in the circuit to the head ends of the cylinders is either leaking or is damaged.

3. Leakage of the oil in the head ends of the cylinders around the seals on the pistons into the rod ends of the cylinders.

4. The check valve in the control valve is not closed.

Multi-Purpose Bucket Cylinder

Drift measurements are the maximum permissible during the time interval shown for the oil temperature in the system.

1. Raise the bucket off the ground.

2. Extend the tilt cylinders fully.

3. Extend Multi-Purpose bucket cylinders to position bowl approximately 1 in. (25.0 mm) from cutting edge. Stop the engine and observe if the bucket cylinder rods retract.

Pressure Relief Valves

The relief valves in the hydraulic system for the loader are part of the loader control valve. The control lever and cover plates must be removed when an adjustment to a relief valve is needed.

CONTROL VALVE
1. Nut. 2. Locknut. 3. Nut. 4. Locknut. 5. Relief valve for bucket dump. 6. Main relief valve.

NOTE: Relief valve for the bucket tilt-back is below relief valve (5) and in the bottom of the same valve section of the loader control valve.

Warm hydraulic oil is needed when making each relief valve test. Start the engine, lift the bucket and hold the bucket in RAISE position for 3 to 5 seconds, lower the bucket and again lift and hold it. This is done to increase the temperature of the hydraulic oil.

1. Lower the bucket, stop the engine and loosen the fill cap on the hydraulic tank.

2. Remove the plug in oil line (8) to the control valve for the loader.

3. Install 5S4648 Hose Assembly where the plug was removed. Install the 1S8937 Valve and 7S8714 Gauge (0 to 4000 psi) in the other end of the hose assembly.

HYDRAULIC PUMP
7. Pump section for loader hydraulic system. 8. Oil line to control valve sections. 9. Pump section for steering hydraulic system. 10. Oil line from supply tank.

Main Relief Valve

The main relief valve (6) is in the inlet section of the loader control valve.

1. Start the engine and run it at high rpm.

2. Move the control lever to the RAISE position.

3. Hold the control lever in RAISE position and look at the test gauge. The correct pressure is 2500 ± 25 psi (17 000 ± 170 kPa).

4. Lower the bucket if it is necessary to make an adjustment to the relief valve.

5. Remove nut (3), loosen locknut (4) and turn the screw. Turn the screw clockwise to get an increase in the pressure setting of the relief valve. Turn the screw counterclockwise to get a decrease.

6. Tighten locknut (4) and make the test again. When the adjustment is correct install nut (3).

Relief Valve for Dump Circuit

Relief valve (5) is in the circuit to the head ends of the hydraulic cylinders which move the bucket to DUMP.

1. Run the engine at high rpm and lift the bucket.

2. Move the control lever to the DUMP position.

3. Hold the lever in the DUMP position and look at the test gauge. The correct pressure is 1200 ± 25 psi (8300 ± 170 kPa).

4. If it is necessary to make an adjustment to the relief valve, lower the bucket.

5. Remove nut (1), loosen locknut (2) and turn the screw. Turn the screw clockwise to get an increase in the pressure setting of the relief valve. Turn the screw counterclockwise to get a decrease.

6. Tighten locknut (2) and make the test again. When the adjustment is correct install nut (1).

Relief Valve for Tilt Back

The relief valve for the circuit to the rod ends of the hydraulic cylinders which move the bucket to TILT BACK is not illustrated. The location of the relief valve is in the bottom of the control valve section that has relief valve (5), for the circuit for DUMP.

1. Run the engine at high rpm.

2. Move the control lever to the TILT BACK position.

3. Hold the lever in TILT BACK position and look at the test gauge. The correct pressure is 2250 ± 25 psi (15 500 ± 170 kPa).

4. If it is necessary to make an adjustment to the relief valve, remove the nut on the screw for adjustment and loosen the locknut. Turn the screw clockwise to get an increase in the pressure setting of the relief valve. Turn the screw counterclockwise to get a decrease.

5. Tighten the locknut on the screw for adjustment and make the test again. When the adjustment is correct install the nut on the screw for adjustment.

NOTE: Some machines have a control valve section next to the valve section for tilt. The adjustments for the relief valves in this control valve section is the same as the adjustments for the relief valves in the valve section for the tilt. The correct pressure for these valves is 3000 ± 25 psi (20 700 ± 170 kPa).

Bucket Positioner (Visual)

VISUAL BUCKET POSITIONER
1. Rod assembly. 2. Rod of right side tilt cylinder. 3. Pipe assembly.

1. Start the engine and position the bucket at the desired angle for digging.

2. The end of rod assembly (1) must be seen in the end of pipe assembly (3). If the end of rod (2) cannot be seen or too much rod is out of pipe assembly (3), an adjustment is needed.

3. Loosen the clamp bolt on rod assembly (1) and move the clamp on the rod of tilt cylinder (2).

4. When the operator for the machine can see the end of rod (1) in pipe assembly (3), tighten the clamp bolt in rod assembly (1).

Lift And Tilt Back Kickouts And Bucket Positioner

The lift and tilt back kickouts and bucket positioner operate only when the engine is running and the alternator is charging the electrical system.

CONTROL LEVER LINKAGE
1. Control lever. 2. Magnet (on lift lever assembly). 3. Electro magnet (not seen). 4. Switch (normally open). 5. Solid state switch. 6. Switch (normally open). 7. Magnet (on tilt lever assembly). 8. Tilt lever assembly.

WIRING DIAGRAM
2. Magnet (on lift lever assembly). 3. Electro magnet. 4. Switch (normally open). 5. Solid state switch. 6. Switch (normally open). 7. Magnet (on tilt lever assembly). 9. Magnet (on lift arm hub). 10. Switch (normally closed, for lift kickout). 11. Switch (normally closed, for bucket positioner and tilt back kickout). 12 & 13. Magnets (on tilt cylinder rod). 14. Switch (closed by oil pressure). 15. Fuse. 16. Battery.

Lift Kickout

1. Start the engine and run it at high idle.

2. Move the control lever to the RAISE position. Electro magnet (3) will hold the lever in RAISE position.

3. The control lever must move to the HOLD position before the lift arms hit the stop. If the kickout did not operate before the lift arms hit the stop or if the kickout was too much before the total lift of the bucket, an adjustment is needed.

LIFT ARM ON RIGHT SIDE
9. Magnet (on clamp). 10. Switch (normally closed).

4. Lower the bucket and stop the engine.

5. Loosen the clamp with magnet (9) and move the magnet position on the hub of the lift arm. Move the magnet nearer to switch (10) if the lift arms had hit the stop. Move the magnet farther away from the switch if the kickout was too much before the stop for the lift arms. Tighten the clamp.

6. Start the engine and test the adjustment. If the kickout is not correct, stop the engine and make another adjustment to the position of the magnet.

Bucket Positioner and Tilt Back Kickout

1. Start the engine and run it at high idle.

2. Hold the control lever in RAISE position until the lift arms are horizontal then move the lever to DUMP position.

3. Move the control lever to TILT BACK position. Electro magnet (3) will hold the lever in TILT BACK position.

4. The control lever must move to the HOLD position when the bucket moves to the digging position. If the digging angle of the bucket is not correct an adjustment is needed.

5. Lower the bucket and stop the engine.

TILT CYLINDER ON RIGHT SIDE
11. Switch (normally closed). 12. Magnet for bucket positioner. 13. Magnet for tilt back kickout.

6. Loosen the clamp with magnet (12) and move the magnet. If the digging angle was too much, move the magnet farther away from switch (11). If the bucket was horizontal and a digging angle is needed, move the magnet nearer the switch. Tighten the clamp.

7. Start the engine and test the adjustment. If the bucket position is not correct for digging, stop the engine and make another adjustment to the position of magnet (12).

8. With the engine running at high idle move the control lever to the TILT BACK position. The electro-magnet will hold the control lever in the TILT BACK position.

9. The control lever must move to the HOLD position before the bucket hits the stop. If the kickout did not operate before the bucket hit the stop an adjustment is needed.

10. Lower the bucket and stop the engine.

11. Loosen the clamp with magnet (13) and move the magnet nearer to switch (11). Tighten the clamp.

12. Start the engine and test the adjustment. If the kickout is not correct, stop the engine and make another adjustment to the position of magnet (13).

Electrical System

Most of the parts in the kickout and bucket positioner electric circuit can be checked with a volt-ohmmeter. A permanent magnet is also used in the tests for the reed-type switches.

FUSE (15) An ohmmeter lead on each end of a fuse will show if the fuse is good or is open and has a failure.

OIL PRESSURE SWITCH (14) The oil pressure switch is "normally open" and is closed by the lubricating oil pressure when the engine is running. Remove the cap from the fuse/holder and remove the fuse. Put the positive lead (+) of the voltmeter in the fuse holder end, from the battery. Put the negative lead (-) on a ground. Voltage shows a failure in the switch. If no voltage is seen make the following test. Start the engine and put the voltmeter leads (+ and -) the same as before. Voltage shows the switch is good. If there is no voltage the switch has a failure.

ELECTRO-MAGNET (3) Disconnect the plug in the wires from solid state switch (5) to the electro-magnet coil. Put one ohmmeter lead in the pin socket and the other on the pin of the plug in the wires to the coil. The ohmmeter will show if the coil has a closed circuit. The coil has a failure if the circuit is open. Note: The ohmmeter can show a closed circuit in a very weak electro-magnet. The cause of a very weak magnet is either low current (voltage) or a "short". A short, is a failure in the coil of an electro-magnet.

SWITCHES (4 and 6) These switches are "normally open" and are closed by a magnet. Pull the switch wire plugs from the jacks in the wires to the switch (two wires for each switch). Put an ohmmeter lead on the plug of each wire to the switch. The ohmmeter shows if there is a failure. If nothing can be seen on the ohmmeter, make the following test: Put the ohmmeter leads on the wires the same as before and then move a magnet near the end of the switch. The ohmmeter shows if the switch is good. If nothing is seen on the ohmmeter the switch has a failure.

SWITCHES (10 and 11) These switches are "normally closed" and are opened by a magnet. Pull the switch wire plugs from the jacks in the wires to the switch (two wires for each switch). Put an ohmmeter lead on the plug of each wire to the switch. If nothing is seen on the ohmmeter the switch has a failure. If the ohmmeter shows the switch is closed, make the following test: Put the ohmmeter leads on the wires the same as before and then move a magnet near the end of the switch. If nothing is seen on the ohmmeter the switch is good. The ohmmeter shows if the switch has a failure.

WIRING DIAGRAM
2. Magnet for lift lever assembly. 3. Electro-magnet. 4. Switch (normally open). 5. Solid state switch. 6. Switch (normally open). 7. Magnet on tilt lever assembly. 9. Magnet on lift arm. 10. Switch (normally closed). 11. Switch (normally closed). 12. Magnet. 13. Magnet. 14. Switch (normally open oil pressure switch). 15. Fuse. 16. Battery.