[Jetex]

I will be checking the oil pressure switches. I don't want to labor the point but it is still possible that even with a single connection on the oil pressure switch, by using logic circuits, an interlock can still be achieved. The discription of the operation of the circuit you posted says the pump relay drops out after 2 secs. after ignition on. What conditions must be met before the relay is energized again? Altough the oil pressure switch has only 1 contact which is no doubt used to turn off the low oil pressure light, the same contact could also be used as an input to a logic circuit. This might then allow the circuit to energize the pump relay again when the oil pressure is correct.

Note that pin 8 of the PCM is named "fuel pump relay control" and although it depicts a simple switch it might in fact be a rather complicated circuit which depends on its operation for other logic inputs. Modern car electronics tend to integrate as much as possible into low cost components. By using a cheap integrated circuit the manufacturer has saved on a set of contacts and terminals on its oil pressure switch.

Please note that this is only wild speculation on my part and I don't want to be drawn into a lengthy argument about this. If I am talking crap you may beat me to death.