Pinpoint Test B: Low Oil Pressure
Engine
Pinpoint Tests
Pinpoint Test B: Low Oil Pressure
Normal Operation
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 on the left front side of the cylinder block then enters the main gallery where it is distributed to the crankshaft main journals and 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 left cylinder head is fed from a drilling into the supply passage feeding the main gallery at the front of the cylinder block. The right cylinder head is fed from a drilling into the rear of the main gallery. Main gallery pressure is 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, the hydraulic lash adjusters and the primary and secondary timing chain tensioners. On Variable Camshaft Timing (VCT) equipped engines, the oil pressure feed for the VCT solenoids, VCT housings and camshaft phaser and sprockets is not reduced. The camshaft lobe and roller followers are lubricated by splash created through valve train operation.
This pinpoint test is intended to diagnose the following:
- Excessive crankshaft end play
- Excessive main bearing clearance
- Excessive connecting rod bearing clearance
- Excessive camshaft bearing cap clearance
- Loose camshaft phaser and sprocket bolt(s) [VCT engines only]
- Loose oil galley plugs
- Loose timing chain tensioner bolts
- Loose VCT housing bolts [VCT engines only]
- Oil pump screen and pickup tube
- Restricted oil flow passages
- Worn or damaged oil pump
PINPOINT TEST B: LOW OIL PRESSURE
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B1 CHECK THE CRANKSHAFT END PLAY
- Check the crankshaft end play. Refer to Crankshaft End Play Crankshaft End Play.
- Is the crankshaft end play within specification?
Yes
GO to B2.
No
REPAIR as necessary.
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B2 VERIFY THE CAMSHAFT BEARING CAPS ARE NOT DAMAGED AND TIGHT
- 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?
Yes
REPAIR as necessary.
No
If the engine is equipped with VCT, GO to B3; for all other engines, GO to B5.
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B3 VERIFY THE CAMSHAFT PHASER AND SPROCKET BOLT(S) ARE TIGHT
- Check that the camshaft phaser and sprocket bolt(s) are tight. Refer to the Specification chart in the appropriate engine system.
- Are the camshaft phaser and sprocket bolt(s) loose?
Yes
REPAIR as necessary.
No
GO to B4.
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B4 VERIFY THE VCT HOUSING BOLT(S) ARE TIGHT [VCT ENGINES ONLY]
- Check that the VCT housing bolts are tight. Refer to the Specification chart in the appropriate engine system.
- Are the VCT housing bolts loose?
Yes
REPAIR as necessary.
No
GO to B5.
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B5 CHECK CAMSHAFT JOURNAL-TO-BEARING CLEARANCE
- 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?
Yes
GO to B6.
No
REPAIR as necessary.
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B6 CHECK FOR RESTRICTED OIL FLOW
- 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?
Yes
REPAIR as necessary.
No
GO to B7.
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B7 CHECK THE TIMING CHAIN TENSIONERS FOR DAMAGE AND VERIFY THE BOLTS ARE TIGHT
- 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?
Yes
REPAIR as necessary.
No
GO to B8.
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B8 CHECK THE OIL PUMP PICKUP TUBE AND SCREEN FOR DAMAGE
- 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?
Yes
REPAIR as necessary.
No
GO to B9.
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B9 CHECK THE OIL PUMP FOR DAMAGE
- Verify the oil pump is not damaged.
- Is oil pump damaged?
Yes
REPAIR as necessary.
No
GO to B10.
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B10 CHECK CRANKSHAFT MAIN BEARING JOURNAL-TO-BEARING CLEARANCE
- 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?
Yes
GO to B11.
No
REPAIR as necessary.
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B11 CHECK CONNECTING ROD BEARING JOURNAL-TO-BEARING CLEARANCE
- 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?
Yes
The concern may have been caused by debris or an incorrect assembly. REPEAT the oil pressure test.
No
REPAIR as necessary.
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