Lubricating Oil System - Overview C Series Page F-8 Section F - Familiarization Low Oil Pressure Low oil pressure can be caused by several lubrication system-related malfunctions. To begin the investigation, determine the engine operating conditions when the low pressure was first observed. Oil Level An improper lubricating oil level can cause low lubricating oil pressure. CAUTION Never operate the engine with the oil level below the low (L) mark or above the high (H) mark. Oil Filter A plugged filter will cause a gradual loss of oil pressure by approximately 69 kPa [10 psi]. This will cause the bypass valve to open, allowing unfiltered oil to flow to internal engine components.
The oil pressure will remain low until a new filter is installed. Inspect the oil gauge and sending unit to make sure they are operating correctly by verifying the pressure with manual gauge. Oil Pressure Gauge - Inspection