Quote:
Originally Posted by MT-2500
I have 60 years of on hands training.
You better get out the good book and read it.
Oil pressure switch is only along for the ride unless the fuel pump relay quits.
To prove it unplug your oil pressure switch and see if engine still runs.
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If what you say is true then perhaps you can explain to me the purpose of the third wire in the oil pressure switch.. If it was a 2 wire switch you would be correct. However, unless I am mistaken, that switch has 3 wires.
The third wire leads back to the ecm. Most wiring diagrams are simplified and only show 2 wires. Now if you notice the fuel pump relay gets it's request straight from the ECM, which turns that request off when the signal from that 3rd wire tells it that there is oil pressure. At that point the only power going to the fuel pump routes through the oil pressure switch.
You are right that the switch and relay are wired parrallel but the side that goes to the relay does nothing until the ecm decides it is needed such as on start up and priming the fuel rail. People get confused when looking at diagrams because they do not show how the ECM controls them.