Pump Flow and Pressure Tests

Before performing the pump flow and pressure test, complete the following checks for conditions which could cause loss of power assist. Take corrective action if necessary.

1. Check pump power steering oil reservoir (3A697) for proper fluid level.

2. Check tires for correct air pressure.

3. Check drive belt (8620) for proper tension.

4. Check power steering pump (3A674) for correct model and vehicle application.

5. Check for correct size power steering pump pulleys (3A733) on power steering pump and engine.

6. Check entire system for damage. Replace parts as necessary.

   If the above items are correct, or have been corrected, and the loss of assist still exists, test the power steering pump flow and pressure to determine whether the trouble is in the power steering pump , power steering gear (3504) or hoses.

Test Equipment

1. Engine tachometer.

2. Thermometer: -17.8° to 148.9°C (0° to 300°F).

3. Rotunda Power Steering System Analyzer 014-00207 or equivalent.

4. Set of adapter fittings.

   The test procedure used in conjunction with the Rotunda Power Steering System Analyzer or equivalent provides a method for checking the complete power steering system. The analyzer can be used on integral or non-integral power steering systems to determine the cause of hard steering and/or lack of assist concerns.

   The analyzer provides readouts for the following:

   • System Back Pressure.
   • Pump Flow.
   • Steering Gear Internal Leakage.
   • Pump Relief Pressure.

   The interpretation of the above readouts will determine which of the following conditions or components are the cause of the concern:

   • Restriction in Hoses or Fittings.
   • Sticking Gear Valve.
   • Inefficient Pump Cam Pack.
   • Sticking Relief Valve.
   • Binding in Suspension.

Test Procedure

1. To connect the analyzer into the steering system, remove the pressure fitting from the power steering pump and connect it into the appropriate adapter of the analyzer.

2. Thread the other adapter of the analyzer into the power steering pump .

3. Connect the analyzer to the adapters. Tighten both connections to 20 Nm (15 lb-ft) maximum.

4. Add power steering fluid to the power steering pump if required. Start the engine, and run it for approximately two minutes at idle.
   
   
   
   

5. Record the following:
   1. Minimum Pump Flow (liters/min.) (gallons/min.) at 78° ± 2°C (172°± 5°F).
   2. System Back Pressure kPa (psi) at 78° ± 2°C (172° ± 5°F) at idle with the gate valve fully open.

6. Partially close the gate valve to build up 5100 kPa (740 psi). Observe and record minimum pump flow liters/min. (gallons/min.) at 78° ± 2°C (172° ± 5°F).

7. Completely close and partially open the gate valve three times. (Do not allow the valve to remain closed for more than five seconds.) Observe and record pressure, kPa (psi).

   Check the chart for the pressure specification listed for the applicable vehicle and engine. If the pressure recorded is lower than the minimum specification listed, replace the flow control valve in the power steering pump .

8. Increase the engine speed from idle to approximately 1500 rpm. Observe and record minimum pump flow, liters/min. (gallons/min.).

9. Check idle speed, and set if necessary. With the engine at idle, turn (or have an assistant turn) the steering wheel (3600) to the left and right stops. Record the pressure and flow at stops.

   Pressure developed at both stops should be nearly the same as maximum power steering pump output pressure.

   At the same time, flow should drop below 1.9L (0.5 gallon/min).

   NOTE: If condition still exists, check ball joints, linkage, etc. Refer to Diagnosis.

10. Turn (or have an assistant turn) steering wheel slightly in both directions, and release quickly while watching the pressure gauge. The needle should move from the normal back pressure reading and snap back as the steering wheel is released. If it comes back slowly or sticks, either the rotary valve in the steering gear is sticking or the steering column tube (3514) is binding. Check the steering column tube before replacing the steering gear valve.

    Remove, disassemble, and clean the rotary valve. If the system is severely contaminated, the gear hoses, control valve, and power steering pump must be completely disassembled and cleaned before reassembly.

11. Disconnect and remove analyzer and connect lines.

System Back Pressure

If pressure is above 1034 kPa (150 psi), check hoses for restrictions.

If the pressure recorded is above the maximum specification listed, the flow control valve in the power steering pump should be removed and cleaned or replaced.

Minimum Pump Flow

If flow drops to a level lower than the value in the chart, disassemble the power steering pump and replace the cam pack. If the pressure plates are cracked or worn, replace them. Continue with diagnosis.

If flow exceeds the maximum free flow specified in chart, the flow control valve in the power steering pump should be removed and cleaned or replaced.

Relief Pressure Test

If flow is below 6 liters/min. (1.6 gallons/min.), the power steering pump may require service. However, at this point continue the diagnosis. Check chart for flow and relief pressure against the vehicle and engine being tested.

Internal Leakage Test

If the pressure does not reach maximum output or flow does not drop below 1.9L (0.5 gallon/min), excessive internal leakage is occurring. Remove and disassemble steering gear. Replace damaged or broken parts. Pay particular attention to the rack piston and valve seals for damage.