Oil Pump Explanation

ENGINE OIL PUMP DESCRIPTION
The vane type engine oil pump is mounted to the underside of the cylinder block and is driven by the oil pump chain off the crankshaft at a 1:1 drive ratio:
This pump location improves efficiency compared to an on-crankshaft location
The pump is driven with a silent chain which is tensioned using a spring loaded tensioner
The pump is not timed to the engine
An internal mechanical ball and spring type relief valve prevents excess pressure in the engine by dumping oil into the sump and provides emergency protection at conditions such as a cold start with high engine speed
The pump has a moving slide mechanism for variable displacement capability and an on-off solenoid for two-stage pressure regulation
The pump and the solenoid are not to be disassembled
Both components are non-serviceable items and are to be replaced as a complete assembly

ENGINE OIL PUMP OPERATION
Oil pump operation as follows:
The engine oil pump features seven vanes and a moving element (Fig 2) #1 that continuously adjusts to maintain a regulated oil pressure supply by varying the displacement of the pump
The pump has two regulated pressure stages of operation controlled by an on/off solenoid (Fig 2) #2
Low pressure mode regulation (solenoid on) is approximately 200 kPa (29 psi) and high pressure mode regulation (solenoid off) is approximately 450 kPa (65 psi)
The Powertrain Control Module (PCM) switches the pump between stages based on engine operating conditions, oil and coolant temperatures, speed and load. Under most typical conditions, the pump will run in low mode from idle up to around 3000 RPM, and switch from low to high mode between 3000 and 4000 RPM
The maximum oil pressure in the engine is limited to 1000 kPa (145 psi) by the relief valve (3)
Pressure in the main oil gallery of the engine can be monitored with diagnostic equipment through the oil pressure sensor mounted on the rear of the oil filter module
The minimum pressure for the engine is 41 kPa (6 psi) at any operating condition
Anything under this pressure could result in damage to critical moving parts

In high pressure mode regulation (solenoid off) main gallery oil pressure (Fig 3) #2 is applied to the moving element #1. The main gallery oil pressure works against spring pressure #3 to move the element to a more concentric location about the pump driveshaft #4 thus reducing displacement and pump output.

In low pressure mode regulation (solenoid on) the energized solenoid opens an additional chamber (Fig 4) #1 to main gallery oil pressure increasing the force on the spring #2 to further reduce displacement and output pressure.

ENGINE OIL PUMP REMOVAL
1. Disconnect and isolate the negative battery cable.
2. Remove the upper oil pan. Refer to PAN, OIL, REMOVAL
3. Remove the oil pump pick-up. Refer to PICK-UP, OIL PUMP, REMOVAL
4. Disconnect the engine wire harness from the oil pump solenoid electrical connector (Fig 5) #1.
5. Remove the connector retaining clip (Fig 6) #1.
6. Depress the connector retention lock tab (Fig 6) #2 to disengage the oil pump solenoid electrical connector from the engine block.
NOTE: Graphic shows the engine timing cover removed for clarity.
7. Push the oil pump solenoid electrical connector into the engine block, rotate the connector slightly CW, push it past the primary chain tensioner mounting bolt (Fig ) #1 and into the engine.
8. Push back the oil pump chain tensioner (Fig 8) #2 and insert a suitable retaining pin #1 such as a 3 mm Allen wrench.
CAUTION: Always reinstall timing chains so that they maintain the same direction of rotation. Inverting a previously run chain on a previously run sprocket will result in excessive wear to both the chain and sprocket.
9. Mark the direction of rotation on the oil pump chain (Fig 9) #3 and sprocket #4 using a paint pen or equivalent to aid in reassembly.
NOTE: There are no timing marks on the oil pump gear or chain. Timing of the oil pump is not required.
10. Remove the oil pump sprocket T45 retaining bolt (Fig 9) #2 and remove the oil pump sprocket #4.
11. Remove the retaining pin (Fig 10) #3 and disengage the oil pump chain tensioner spring #1 from the dowel pin #2.
12. Remove the oil pump chain tensioner from the oil pump.
13. Remove the four oil pump bolts (Fig 11) #1 and remove the oil pump (Fig 11) #3.

ENGINE OIL PUMP INSPECTION
NOTE: The Oil pump is released as an assembly. The assembly includes both the pump and the solenoid. There are no serviceable sub-assembly components. In the event the oil pump or solenoid are not functioning or out of specification they must be replaced as an assembly.
1. Inspect the solenoid wires (Fig 12) #1 for cuts or chafing.
2. Inspect the condition of the connector O-ring seal (Fig 12) #3.

ENGINE OIL PUMP INSTALLATION
1. Align the locator pins (Fig 11) #2 to the engine block and install the oil pump (Fig 11) #3 with four bolts (Fig 11) #1. Tighten the bolts to 12 N.m (106 in. lbs.).
2. Install the oil pump chain tensioner on the oil pump.
3. Position the oil pump chain tensioner spring (Fig 10) #1 above the dowel pin (Fig 10) #2.
4. Push back the oil pump chain tensioner and insert a suitable retaining pin (Fig 10) #3 such as a 3 mm Allen wrench.
NOTE: There are no timing marks on the oil pump gear or chain. Timing of the oil pump is not required.

CAUTION: Always reinstall timing chains so that they maintain the same direction of rotation. Inverting a previously run chain on a previously run sprocket will result in excessive wear to both the chain and sprocket.

5. Place the oil pump sprocket (Fig 9) #4 into the oil pump chain (Fig 9) #3. Align the oil pump sprocket with the oil pump shaft and install the sprocket. Install the T45 retaining bolt (Fig 9) #2 and tighten to 25 N.m (18 ft. lbs.).
6. Remove the retaining pin (Fig 9) #1. Verify that the oil pump chain is centered on the tensioner and crankshaft sprocket.
7. Rotate the crankshaft CW one complete revolution to verify proper oil pump chain installation.
NOTE: Graphic shows the engine timing cover removed for clarity.
8. Position the oil pump solenoid electrical connector (Fig 7) #2 into the engine block. Rotate the connector so that it can be pushed past the primary chain tensioner mounting bolt (Fig 7) #1. Then rotate the connector slightly CCW and push it into the engine block until it locks in place.
9. Verify that the oil pump solenoid electrical connector retention lock tab (Fig 6) #2 is engaged to the engine block.
10. Install the connector retaining clip (Fig 6) # 1.
11. Connect the engine wire harness to the oil pump solenoid electrical connector (Fig 5) #1.
12. Install the oil pump pick-up. Refer to PICK-UP, OIL PUMP, INSTALLATION
13. Install the oil pan. Refer to PAN, OIL, INSTALLATION
14. If removed, install the oil filter and fill the engine crankcase with the proper oil to the correct level. Refer to STANDARD PROCEDURE
15. Connect the negative battery cable and tighten nut to 5 N.m (45 in. lbs.).
16. Start and run the engine until it reaches normal operating temperature.

CAUTION: A MIL or low oil pressure indicator that remains illuminated for more than 2 seconds may indicate low or no engine oil pressure. Stop the engine and investigate the cause of the indication.