this is a 1994 chevy blazer sport 5.7L . My oil pressure guage is fluctuating between 0 - 40 and when i coast falls to 0 I'm thinking my oil pump is dieing ?? I am wondering is their a sensor that may be failing ?? and also if I need a new pump whats involved with replacing this pump and does it involve pulling the engine ?? With best regards, Jim kidja@yahoo.com