Help please, oil pressure sender has TWO wires.

[Dan Juday]

What's up with that? When I did the swap in my '73 it had one wire to the gauge. Now I'm doing a swap on a '78 and it has two wires. One goes through the firewall and the other goes to the batch of relays on the passenger side fender well. I only need the gauge to work. Do I need both wires? Both wires are yellow/black.

Thanks,

Dan

[zcarnut]

One wire is for the oil gauge and the other wire goes to a switch inside the oil sending unit which closes once you have any oil pressure. This wire goes to a relay in the passenger kick panel that controls the fuel pump.

 

So, if you lose oil pressure then the fuel pump is turned off.

 

This is part of a saftey feature. If you have a accident and the engine stops running but the ignition key is in the ON position, you want the fuel pump to stop so as not to feed a potential fire.

 

Before 1978 Nissan used a sense voltage from the alternator and/or a signal from the airflow meter to determine if the engine was running. However, it was shown that a fuel injected engine would operate even upside down, so a signal from the oil pressure sending unit was then used instead.

[Dan Juday]

Thanks Steve,

This is what I had presumed but I wanted confirmation.