Hi i have just started my 308 and have no oil pressure,the motor came out of a donor car and was running fine when i bought it.The only thing i did before putting it in another car was put it on an engine stand and put another sump on it so that means the engine was upside down for a while. i took the oil pressure sender out and primed the pump and the oil filter is full and i know its not the gauge.when the motor was upside down would it be possible for the shaft that drives the pump to disengage from the cam? any help or ideas would be appreciated thanks