Troubleshooting Guide for 740 Ejector Manifold{5050, 5264} Caterpillar

Articulated Truck:

740 EJECTOR (S/N: B1R1-UP; AZZ1-UP)

740B EJECTOR (S/N: L4F1-UP; T4S1-UP)

Introduction

ReferenceOperation and Maintenance Manual, SEBU8346, "740B Ejector Articulated Truck"

ReferenceOperation and Maintenance Manual, SEBU7573, "740 Ejector Articulated Truck"

ReferenceOperation and Maintenance Manual, SEBU7927, "740 Ejector Articulated Truck"

ReferenceSpecifications, RENR5173, "740 Ejector Articulated Truck Steering, Suspension, and Ejector Body Hydraulic Systems"

ReferenceSpecifications, RENR6735, "735, 740, and 740 EJECTOR Articulated Trucks Machine Systems"

ReferenceSystems Operation, Testing and Adjusting, RENR5174, "740 Ejector Articulated Truck Ejector, Steering, Suspension, and Fan Drive Systems"

ReferenceSpecifications, UENR0208, "735B, 740B, and 740B Ejector Articulated Trucks Machine Systems"

ReferenceSystems Operation, Testing and Adjusting, UENR0210, "735B, 740B, and 740B Ejector Articulated Trucks Machine Systems"

Illustration 1	g02351725
Ejector manifold on the rear frame

This special instruction provides a comprehensive troubleshooting guide for the ejector manifold on the listed machines. Therefore, read the information that is provided in this publication before you begin troubleshooting. Also, read the information in the service manual for your machine that is referenced in this instruction. Be sure to read all of the safety information in the references above before performing any troubleshooting procedures.

Ensure that checks have been made to all other components of the ejector system. Ensure any fault in operation of the ejector system is not caused by one of the following components:

• Hoist or ejector control valve

• Ejector cylinder

• Hoist or ejector gear pump

• Brake piston pump

• Check and pressure reducing valve

• Incorrect hose routing

740 Ejector Manifold Troubleshooting Procedures

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Personal injury or death can result from sudden machine movement. Personnel can be injured during the steering check. To help prevent possible personal injury, keep all personnel away from the machine or in clear view of the operator when the machine is in operation during steering checks.

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Sudden movement of the machine or release of oil under pressure can cause injury to persons on or near the machine. To prevent possible injury, perform the procedure that follows before testing and adjusting the hydraulic system.

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Do not check for leaks with your hands. Pin hole (very small) leaks can result in a high velocity oil stream that will be invisible close to the hose. This oil can penetrate the skin and cause personal injury. Use cardboard or paper to locate pin hole leaks.

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Hot oil and hot components can cause personal injury. Do not allow hot oil or hot components to contact skin.

Machine Preparation

Warm up and test the machine in order to make sure that the machine is ready to troubleshoot.

1. Warm the oil, refer to the Testing and Adjusting, "General Information" manual for your machine.

2. Conduct a visual inspection of the machine in order to detect any leaks. Refer to Testing and Adjusting, "Visual Inspection" for your machine.

3. Check that the hydraulic level is correct. Refer to Operation and Maintenance Manual, "Ejector System and Brake System Oil Level - Check" for your machine.

4. Verify that the oil is at the proper level and warm. Verify that there are no external leaks. Recheck that the failed machine function is present. Failures of machine functions can be caused by the cold oil or low oil. Failures can be caused by an external leak.

5. Check for obvious damage to components.

Troubleshooting of the Ejector Manifold

Illustration 2	g02351637
(E1) Eject Side Supply Return (E2) Ejector Cylinder Piston Side (ER) Ejector Cylinder Rod Side (EHP) Ejector Cylinder Test Point Piston Side (ERP) Ejector Cylinder Test Point Rod Side (BP) Brake Pump Supply (CE) Control Signal Eject (CR CRV) Control Signal Retract (T) Return to Tank (GR) Tailgate Cylinder Rod Side (TGH) Tailgate Cylinder Piston Side

Problem 1

The ejector cylinder miss-stages during an eject cycle with no load in the body.

Potential Root Cause: Fault in regulation of back pressure on rod side of the cylinder allows incorrect staging of the cylinder.

Possible Component Failures in the Ejector Manifold:

• 208-1479 Sequence Valve Gp (8)

Problem 2

The ejector blade fails to eject.

Potential Root Cause: Failure to allow hydraulic oil on the cylinder rod side to flow out to tank or combine with supply oil to the cylinder piston side. Trapped oil in the rod side of the cylinder causes a hydraulic lock.

Possible Component Failures in the Ejector Manifold:

• 208-1479 Sequence Valve Gp (8)

• 208-1476 Diverter Valve Gp (9)

Problem 3

The ejector blade ejects slowly.

Potential Root Cause: Failure of the system to allow hydraulic oil on the cylinder rod side to combine with supply oil to the cylinder piston side. Failure to add brake system oil to the flow of oil to the piston side of the cylinder. Without additional oil from the cylinder rod side and brake system, the hoist pump does not generate sufficient flow. The insufficient flow prevents the cylinder to eject at full speed.

Possible Component Failures in the Ejector Manifold:

• 208-1479 Sequence Valve Gp (8)

• 208-1476 Diverter Valve Gp (9)

• 192-8833 Diverter Valve Gp (10)

• 224-9385 Sequence Valve Gp (12)

• 208-1475 Load Control Valve Gp (1)

• 214-0081 Load Control Valve Gp (2)

• 215-9101 Flow Control Valve Gp (4)

• 208-1477 Relief Valve Gp (7)

Problem 4

The ejector blade fails to retract.

Potential Root Cause: The supply oil is blocked. The supply oil is diverted to piston side of the ejector cylinder. The supply oil is relieving to tank.

Possible Component Failures in the Ejector Manifold:

• 215-9101 Flow Control Valve Gp (4)

• 208-1477 Relief Valve Gp (7)

• 208-1476 Diverter Valve Gp (9)

• 192-8833 Diverter Valve Gp (10)

• 224-9385 Sequence Valve Gp (12)

Problem 5

The ejector blade retracts slowly.

Potential Root Cause: The supply oil is relieving to tank.

Possible Component Failures in the Ejector Manifold:

• 215-9101 Flow Control Valve Gp (4)

• 208-1477 Relief Valve Gp (7)

Problem 6

The ejector cylinder extends in the HOLD position.

Potential Root Cause: Oil pressure going to the rod side of the ejector cylinder and bypassing the piston rings to fill the piston side of the ejector cylinder.

Possible Component Failures in the Ejector Manifold:

• 208-1476 Diverter Valve Gp (9)

• 192-8833 Diverter Valve Gp (10)

• 224-9385 Sequence Valve Gp (12)

Problem 7

The tailgate fails to open.

Potential Root Cause: The load control valve does not open or the in circuit load control valve is not suitable for the type of load.

Possible Component Failures in the Ejector Manifold:

• 208-1475 Load Control Valve Gp (1)

• 214-0081 Load Control Valve Gp (2)

• 208-1480 Flow Control Valve Gp (3)

Problem 8

The tailgate drifts open during operation.

Potential Root Cause: Leakage across the load control valves or leakage via the manual lower load valve to tank.

Possible Component Failures in the Ejector Manifold:

• 208-1475 Load Control Valve Gp (1)

• 214-0081 Load Control Valve Gp (2)

• 215-9101 Flow Control Valve Gp (4)

• 195-9088 Check Valve Gp (6)

Problem 9

The tailgate fails to close or closes slowly.

Potential Root Cause: The supply oil is restricted due to blockage at orifice or check valve. Oil is leaking to tank via manual lower load valve.

Possible Component Failures in the Ejector Manifold:

• 215-9101 Flow Control Valve Gp (4)

• 215-9105 Orifice Plug (5)

• 195-9088 Check Valve Gp (6)

Problem 10

Low brake pressure warnings,

Potential Root Cause: Resolve any fault in the brake system by referring to Systems Operation, Testing and Adjusting, RENR5129, "735, 740 and 740 Ejector Articulated Trucks Braking System." Component issues in the ejector manifold might drain brake pump pressure to tank or reduce the responsiveness of the brake pump.

Possible Component Failures in the Ejector Manifold:

• 194-1723 Check Valve Gp (11)

• 224-9385 Sequence Valve Gp (12)

Ejector Manifold Schematic and Components

Illustration 3	g02351637
(E1) Eject Side Supply Return (E2) Ejector Cylinder Piston Side (ER) Ejector Cylinder Rod Side (EHP) Ejector Cylinder Test Point Piston Side (ERP) Ejector Cylinder Test Point Rod Side (BP) Brake Pump Supply (CE) Control Signal Eject (CR CRV) Control Signal Retract (T) Return to Tank (GR) Tailgate Cylinder Rod Side (TGH) Tailgate Cylinder Piston Side

Refer to Illustration 3 for a schematic of the ejector manifold and constituent parts. Refer to Table 1 for a list of the components in the ejector manifold cross referenced with observable faults.

Refer to the following information about the purpose of each of the components in the ejector manifold. The information describes the effects that each component has on the operation of the ejector system if the component fails to work to specification.

Illustration 4	g02351723

Adding 208-1475 Load Control Valve (1) to the tailgate circuit with 214-0081 Load Control Valve (2), allows the tailgate to open for light material. Refer to 208-1480 Flow Control Valve Gp (3) .

• If the load valve is stuck closed, tailgate will not open or fail to open early enough for light material loads

• If the load valve is leaking, the tailgate will drift open if the load valve is in circuit.

• If the valve is open, flow is directed to tank reducing eject times

Illustration 5	g02351742

When 214-0081 Load Control Valve (2) is the only load control valve in the tailgate circuit, the tailgate will open for normal to heavy material. This load control valve selection is the factory default. Refer to 208-1480 Flow Control Valve Gp (3) .

• If the valve is stuck closed, the tailgate will not lower unless load valve (1) is in circuit.

• If the load valve is leaking, the tailgate will drift open.

• If the valve is open, flow is directed to tank reducing eject times.

Illustration 6	g02351749

208-1480 Flow Control Valve Gp (3) controls tailgate opening presure. This group selects either load control valve (1) in circuit or both load control valve (1) and load control valve (2) are in circuit. In normal operation, load control valve (2) is in circuit. When hauling light material where a lower operating pressure is required by the tailgate, both load control valve (1) and (2) should be in circuit.

• If the flow control valve is stuck closed, only load control valve (2) will be in circuit. Light material loads will have problems opening the tailgate.

• If the flow control is stuck open, both load control valve (1) and load control valve (2) will be in circuit. The tailgate will open early for medium heavy loads. Also, the tailgate will potentially drift open underload when the ejector control lever is in the HOLD position or the engine is off.

Illustration 7	g02351754

215-9101 Flow Control Valve Gp (4) is used for manually lowering the tailgate and for purging the ejector cylinder.

• If the flow control valve fails to open, the tailgate will not manually lower.

• If the flow control valve is leaking, the tailgate will drift down.

• If the flow control valve is leaking, there will be a reduction in eject and retract times due to the volume loss of oil.

Illustration 8	g02351756

215-9105 Orifice Plug (5) regulates the tailgate closing speed.

• If the orifice is plugged, the tailgate will not close.

Illustration 9	g02351796

195-9088 Check Valve Gp (6) controls oil flow from the break system to close the tailgate.

• If the check valve is leaking, the tailgate will drift open and or close slowly.

Illustration 10	g02351812

208-1477 Relief Valve Gp (7) protects the rod end of the ejector cylinder from over pressure.

Note: Oil from the rod end of the ejector cylinder does not return to tank through the ejector control valve. The oil is used to make up supply oil to the piston side of the ejector cylinder. If this flow is restricted or blocked to the piston side of the ejector cylinder, the relief valve will open to protect the system.

• If the relief valve is set too low, the tailgate will not close and the ejector blade will not retract.

• If the relief valve is set too high, there will be potential damage to components

• If the relief valve is leaking, the ejector blade will be slow to eject and retract. Also, the tailgate will be slow to close.

Illustration 11	g02351810

208-1479 Sequence Valve Gp (8) ensures that the ejector cylinder extends in the correct sequence. Also, the sequence valve allows return oil from the ejector cylinder rod side to supplement supply oil to the piston side of the ejector cylinder.

• If the sequence valve is stuck open, there will be potential for the ejector cylinder to extend in the incorrect sequence and miss stage. This fault can only occur when the ejector blade is ejected with no load in the body.

• If the sequence valve is stuck closed, the eject speed will be slow. The ejector blade might stall due to reduced oil supply and pressure on the rod side of the piston.

Illustration 12	g02351830

208-1476 Diverter Valve Gp (9) controls oil flow from the cylinder rod end and brake pump to the cylinder piston end during the eject cycle.

• If the diverter valve is stuck closed, the eject speed will be slow. The ejector cylinder might stall due to reduced oil supply and the increase in pressure on the rod side of the piston.

• If the diverter valve is stuck open, the ejector blade will fail to retract. At the same time, the ejector blade may extend while the ejector control lever is in the RETRACT position. This condition is due to oil pressure on both the rod and head sides of the piston.

Illustration 13	g02351832

192-8833 Diverter Valve Gp (10) controls the operation of sequence valve (12). The diverter valve provides a drain to allow the sequence valve to operate and let brake pump oil into the manifold. Brake pump oil supplements gear pump oil used during the eject cycle and brake pump oil is used during the retract cycle. The valve stem is held closed by equal pilot oil pressure on both ends of the stem. Pressure decay in the one of the pilot oil lines causes the stem to move to an open position.

• If the diverter valve is stuck in the closed position with the valve stem centered, the eject speed will be slow. The ejector blade will not retract with the diverter valve stuck in the closed position.

• If the diverter valve is stuck in open position, the valve stem will be moved to either side. This condition has no effect on the eject or retract cycle of the ejector blade. But, if the ejector control is placed in the HOLD position, brake oil pressure feeds into the rod end of the ejector cylinder. This oil bypasses the piston rings and causes the ejector cylinder to extend.

Illustration 14	g02351925

The 194-1723 Check Valve Gp (11) prevents back flow to the brake pump.

• If the check valve is leaking, there might be low brake pressure warnings if back pressure from the ejector system disrupts the brake charging system.

Illustration 15	g02351926

224-9385 Sequence Valve Gp (12) provides priority to the brake charging system. This valve controls brake pump supply to supplement the eject function. The sequence valve also controls the brake pump supply as supply for the retract system.

• If the sequence valve is stuck open, the brake oil pressure can make the ejector cylinder extend when the control is in HOLD position. When the ejector control is in the EJECT or RETRACT positions, the sequence valve losses priority control for brake charging. This condition might cause a low-pressure brake warning especially when the engine is at low idle.

• If the sequence valve is plugged at the internal orifice, brake oil pressure can make the blade extend when the control is in HOLD position. When the ejector control is in the EJECT or RETRACT positions, the sequence valve losses priority control for brake charging. This condition might cause a low-pressure brake warning especially when the engine is at low idle.

• If the sequence valve is stuck closed, the ejector blade is slow to eject and fails to retract. The tailgate will also fail to close.

• If the sequence valve is set higher than the brake system supply pressure, the sequence valve will not open. This condition will cause the ejector blade to be slow to eject and fail to retract. This condition will also cause the tailgate to fail to close.

• If the sequence valve is set too low during ejecting and retracting, the sequence valve poorly controls priority for brake charging. This condition might cause a low-pressure brake warning especially when the engine is at low idle.