Oil Pressure Gauge - High Reading Especially at Start Up
BULLETIN NUMBER: 93-8C-31SECTION: 8C
NUMBER: 3
CORPORATE
REFERENCE NUMBER: 268306
DATE: November 1992
SUBJECT:
INFORMATION ON HIGH OIL PRESSURE READING AT START UP
MODELS:
1992-93 ALL LIGHT TRUCKS WITH 4.3L, 5.0L, 5.7L ENGINE (RPO LB4, L35, L03, L05)
Some 1992-93 Light Duty Trucks with oil pressure gauges and 4.3L, 5.0L, or 5.7L engines built after 6/15/92 may exhibit high oil pressure readings at start up, especially when cold.
Engines produced after 6/15/92 were built with an enhanced oil pump capable of producing approximately 10 psi more pressure than the previous pump. This may cause the gauge to temporarily read as high as 60 psi during start up. The length of time the oil pressure stays high will depend on oil viscosity, engine temperature, and ambient temperature.
This condition will not cause any ill effects on the engine or gauge and unless there are other symptoms to indicate an oil pressure or gauge problem such as very low pressure after warm rapid fluctuation, engine noise etc. no repairs should be attempted. Replacing the oil pump or gauge system parts will not be effective.
Build date of the engine can be verified by the engine code. The location of this code is illustrated in Section 0A of the appropriate service manual. The engine code is 8 positions long with an alpha plant designator in the first position, followed in the next four positions by the month and day; for example T0615xxx would indicate that this engine was built in Tonawanda on June 15th and, therefore, has the enhanced oil pump. The plant code is insignificant because all 4.3L, 5.0L, and 5.7L plants began using the enhanced oil pump on the same day.