what is the yel/blk wire for on the oil pressure switch?

[Guest nwzeeman]

I am ready to install the 280Z oil pressure switch onto the back of the intake manifold on my 350 sbc...the switch has two terminals on it, and the connector from the original 1978 harness has a yellow and a yellow/black wire going to it. Problem is...I snipped off the yel/black wire when I was redoing the harness, thinking it was not needed.

 

I traced the yellow wire back and it goes to the oil pressure gauge, but I have no idea what the yel/black wire is for. Was it for an idiot light or something?

 

Can anyone confirm that I only need the yellow wire, and not both. If I need the yel/black wire, can someone tell me where it is routed back to, as I don't see it on any of my wiring diagrams.

 

Thanks for any help. -Rod

[DaleMX]

On my 280 the black/yellow was the starter wire.

[skipzoomie]

Early first generation Z's had a connection to the fuel pump at the airflow meter. I think that was changed in 77 and that connection was switched to the oil pressure switch. Hence the two wire connector. You could wire your SBC so that it could also work the same. If the oil pressure goes away the fuel pump will be turned off and the engine will also be shut off.

[BrandonsZ]

Early first generation Z's had a connection to the fuel pump at the airflow meter. I think that was changed in 77 and that connection was switched to the oil pressure switch. Hence the two wire connector. You could wire your SBC so that it could also work the same. If the oil pressure goes away the fuel pump will be turned off and the engine will also be shut off.

 

Obviously, run it to a relay, and start the car first, get up to presure, and check the wire to be sure before you hook it up to the pump, you may want to run a seperate switch for the fuel pump to defeat this as well because the oil pressure in a sbc takes a while to build to the switch, so if you don't fdrive it for a while and the carb is dry you'll be cranking all day (I've heard).

 

I hooked a switch to the fuel pump relay which can manually trip it just in case I wanted to "prime" the engine. I haven't needed to use it yet though, the holley pressure switch works pretty quick and I hear the pump kick in in about 3 seconds after it starts, but not while cranking. I have about 30 sec-1 minute of fuel to run the engine from the float bowls even when the fuel filters are dry (they're clear). FYI.

[Georgia Flash]

Rod,

 

On my 76 280 the oil pressure sending unit on the passenger side of the engine had a green wire running to it. Things like this confused me when I started wiring up my 350. The JTR book specified using the "yellow/black" wire that went to the oil pressure sender. However, once I traced the green wire back into the harness to a connector with a few prongs on it, I discovered that it turned into a yellow/black wire on the other side of that connector.

 

I simply hooked up the Datsun sender to the brass elbow that I had bought from the hardware store (see page 3-9 in the JTR manual) and then hooked up the yellow/black wire to that. It works fine.

 

I hope that this helps. It really is very simple to wire once you get started. Believe me I know because I was very nervous about this when I began.

 

Let me know if you have any other questions concerning the wiring on the 280Z while it is still fresh on my mind.