Ever since i got my k5 last year, the oil pressure gauge hasn't worked properly. The gauge reads anywhere from 15 to 40 psi, but it never moves after being turned on. wherever the gauge is when the engine starts is where it stays(usually around 35 psi). I want to replace the sending unit, but I don't know where it is on my engine. Can someone please tell me where to find the sending unit on an 85 305.