Pinpoint Tests

Diagnostic Routine A

Diagnostic Overview

Low Oil Pressure

Normal Operation and Fault Conditions

Oil is drawn into the oil pump through the oil pump screen and pickup tube in the sump of the oil pan. Oil is pumped through the oil filter and then enters the main gallery where it is distributed to the crankshaft main journals, to both cylinder heads. From the main journals, the oil is routed through cross-drilled passages in the crankshaft to lubricate the connecting rod bearings. Controlled leakage through the crankshaft main bearings and connecting rod bearings is slung radially outward to cool and lubricate the cylinder walls as well as the entire connecting rod, piston and piston ring assembly. The cylinder heads are fed from a drilling into the supply passage feeding the main gallery. Main gallery pressure is sent through VCT (Variable Camshaft Timing) circuit and reduced as it enters the cylinder head galleries through fixed serviceable orifices, located at the upper part of the feed passages. It is this reduced pressure in the cylinder head galleries which feed the camshaft journals, rocker arm shafts and the primary and/or secondary timing chain tensioners. The camshaft lobe, roller followers, rocker arms and valve tappets are lubricated by splash created through valve train operation.

Low oil pressure can be attributed to internal engine conditions including:

- Excessive crankshaft end play

- Excessive main bearing clearance

- Excessive connecting rod bearing clearance

- Excessive camshaft bearing cap clearance

- Loose oil galley plugs

- Loose timing chain tensioner bolts

- Oil pump screen and pickup tube

- Restricted oil flow passages

- Worn or damaged oil pump

Pinpoint Test

1. CHECK THE CRANKSHAFT END PLAY

1. Check the crankshaft end play. Refer to Crankshaft End Play.

Is the crankshaft end play within specification?






2. VERIFY THE CAMSHAFT BEARING CAPS ARE NOT DAMAGED AND TIGHT

1. Check that the camshaft bearing caps are not damaged and the bolts are properly tightened. Refer to the Specification chart in the appropriate engine system.

Are the camshaft bearing caps loose or damaged?






3. CHECK CAMSHAFT JOURNAL-TO-BEARING CLEARANCE

1. Check the camshaft journal-to-bearing clearance. Refer to the Specification chart in the appropriate engine system.

Is camshaft journal-to-bearing clearance within specification?






4. CHECK FOR RESTRICTED OIL FLOW

1. Verify the oil supply and return passages are not plugged and clean of debris. Refer to the oil flow chart in the appropriate engine system.

Is oil flow restricted?






5. CHECK THE TIMING CHAIN TENSIONERS FOR DAMAGE AND VERIFY THE BOLTS ARE TIGHT

1. Check that the timing chain tensioners are not damaged or the bolts are loose. Refer to the Specification chart in the appropriate engine system.

Are the timing chain tensioners damaged or bolts loose?






6. CHECK THE OIL PUMP PICKUP TUBE AND SCREEN FOR DAMAGE

1. Check that the oil pump pickup tube and screen is not plugged, cracked or that the bolts are loose. Refer to the Specification chart in the appropriate engine system.

Is the oil pump screen and pickup tube damaged or loose?






7. CHECK THE OIL PUMP FOR DAMAGE

1. Verify the oil pump is not damaged.

Is oil pump damaged?






8. CHECK CRANKSHAFT MAIN BEARING JOURNAL-TO-BEARING CLEARANCE

1. Check the crankshaft main bearing journal-to-bearing clearance. Refer to the Specification chart in the appropriate engine system.

Is crankshaft main bearing journal-to-bearing clearance within specification?






9. CHECK CONNECTING ROD BEARING JOURNAL-TO-BEARING CLEARANCE

1. Check the connecting rod bearing journal-to-bearing clearance. Refer to the Specification chart in the appropriate engine system.

Is connecting rod bearing journal-to-bearing clearance within specification?