Oil pressure switch ???

[bbgun24]

I have a 1990 4.3L w/ the spitfire ignition. I am wiring in a electronic fuel pump as I switched motors and the new motor doesnt have hole for mech. pump. Im wondering if I can just buy a new pressure switch with two leads on it?? The current switch has just one lead. I would think that the ignition system doesnt require a specific pressure switch but maybe I am wrong. Does anyone have any thoughts or suggestions on this?? Thanks.

 

[drem312]

Re: Oil pressure switch ???

I just did a switch on mine it was a three prong carter switch. One wire to the y

 

[bbgun24]

Re: Oil pressure switch ???

Ok, Im just concerned that if I use a different oil pressure switch it is going to screw up the electronic ignition?? Do all switches open at the same pressure?? Would it make more sense to just splice the fuel pump wire into the current wire coming from the pressure switch??

 

[Don S]

Re: Oil pressure switch ???

The 3 prong pressure switches are nothing more than universal switches. They have contacts for both N.O. and N.C. use.
You need a N.O. (Normally Open) pressure switch with a 3-7 psi closing pressure. Here is a Mercruiser drawing showing how the wiring is done. Note: The purple/yellow wire from the starter is what runs the fuel pump while the engine is cranking, the oil pressure switch only comes into play when oil pressure builds, closes the switch and powers the pump.

 

[bbgun24]

Re: Oil pressure switch ???

ok, so if I get a 3 prong switch it will have a NO-common-NC prongs correct??? I will hook the fuel pump to the NO, I will hook the wire coming from the alternator to the common (this is where im a little confused) and I will hook the current wire for the ignition system to the NC correct??? So that would mean that the 1-prong switch for the ignition system that I currently have is NC?? thanks for the help.

 

[Don S]

Re: Oil pressure switch ???

You hook the power to the purple wire, not just "to the alternator" don't forget, that is a Mercruiser drawing, not OMC. You have to find a connection in the purple wire (Ignition) for the power side of the OP switch.

 

[bbgun24]

Re: Oil pressure switch ???

I will find a place to attach to the purple wire and not the alt. thanks. The part number for my current pressure switch is 0379948, can anybody tell me if this is a NO or NC switch?? If it is a NO switch will it be possible to wire in the electric fuel pump?? Would I just not use the prong that is NC at all?? Thanks.