Oil pressure Switch Wiring For Fuel Pump

[shawnn82]

I just received a marine fuel pump and a 3 post Oil pressure switch to run it. I have drawn up a schematic of what i think is the correct wiring. With How i have it wired, will the pump shut off if the engine dies? or do i have the NO and NC posts on the OP switch on backwards in relation to the fuel pump relay?

 

[Don S]

Re: Oil pressure Switch Wiring For Fuel Pump

You have the NO and NC on your drawing reversed, along with the 85 and 86 terminals on the fuel pump relay.
For the power for the switch that you now have coming from the starter, it should be coming from the purple wire, that way the power to the oil pressure switch gets shutoff when the switch is turned off. It won't happen with the way you now have it.

 

[shawnn82]

Re: Oil pressure Switch Wiring For Fuel Pump

You have the NO and NC on your drawing reversed, along with the 85 and 86 terminals on the fuel pump relay.

Thanks Don, I have re-drawn it. Does it look about right now?
I can build a computer with my eyes closed but when it comes to engines, i have absolutely no idea of how anything works. I have learned a lot from this forum since i got this boat (my first boat) 4 months ago, so i appreciate the patience with my lack of knowledge when it comes to everything marine! Here is the pic -->

 

[Maclin]

Re: Oil pressure Switch Wiring For Fuel Pump

How will the fuel pump get power during cranking until oil pressure comes up. It is standard to have a bypass circuit that gets power to the fuel pump while cranking.

I do not like the relay having power all the time from the battery. In my opinion the relay should not have 12v available to "pass on" unless the key is in On/Run.

 

[Don S]

Re: Oil pressure Switch Wiring For Fuel Pump

How will the fuel pump get power during cranking until oil pressure comes up.

On the oil pressure switch, power to the pump comes from the NC terminal to the C terminal when cranking.

And I agree about coming off the starter, that is why I replied with the quote below. He must have missed it.

For the power for the switch that you now have coming from the starter, it should be coming from the purple wire, that way the power to the oil pressure switch gets shutoff when the switch is turned off. It won't happen with the way you now have it.

 

[shawnn82]

Re: Oil pressure Switch Wiring For Fuel Pump

For the power for the switch that you now have coming from the starter, it should be coming from the purple wire

Which purple wire? the one going to condensor or coil? or to ignition switch (i)

"I do not like the relay having power all the time from the battery"
Where should i hook up this wire too (pin 30 on fuel pump relay)?

It would be easier to see a diagram if anyones up for it. Having trouble gettin my pea sized brain to absorb all this lol

 

[Don S]

Re: Oil pressure Switch Wiring For Fuel Pump

Which purple wire? the one going to condensor or coil? or to ignition switch (i)

Purple wires do not go to condensers, they go to coil if not hooked to resistor wire or ballast resistor before getting to the coil.
You have the advantage, you know what engine your boat has, we don't.

 

[Maclin]

Re: Oil pressure Switch Wiring For Fuel Pump

I had some trouble following the "humps" until I discovered the magnifying glass... thanks Don S for the assurance that it was getting power during cranking.



Your diagram does not have the pin number configuration for the harness connectors, so I will use the relative positions top to bottom for reference.

The lead you have coming from the battery positive terminal to the fuel pump relay pin 30 should be coming from the TOP purple wire, on the engine side but BEFORE any ballast resistor component if any. That way it can only have power if the key is in On/Run.

Also, the NC Normally Closed terminal on the oil pressure switch should probably be fed from the engine side of the harness from the yellow/red wiring that feeds the starter relay exciter pin 85. In essence it is wired to the same place now, but from the helm side of the harness. Just seems better to have the wiring all on the engine side.

Having two purple wires is confusing, but the LOWER purple wire is really just an extension of the WHITE lead from the coil negative post that goes to the breaker points (or other triggering device). The GREY wire is the tach wire and is only on the helm side of the harness. The connector is used to make the "splice" for this junction.


I apologize for just text. I wish I could diagram this, but I lost my Visio and Cad when my job (and me) got outsourced.

 

[shawnn82]

Re: Oil pressure Switch Wiring For Fuel Pump

The lead you have coming from the battery positive terminal to the fuel pump relay pin 30 should be coming from the TOP purple wire, on the engine side but BEFORE any ballast resistor component if any. That way it can only have power if the key is in On/Run.

Also, the NC Normally Closed terminal on the oil pressure switch should probably be fed from the engine side of the harness from the yellow/red wiring that feeds the starter relay exciter pin 85. In essence it is wired to the same place now, but from the helm side of the harness. Just seems better to have the wiring all on the engine side.

Having two purple wires is confusing, but the LOWER purple wire is really just an extension of the WHITE lead from the coil negative post that goes to the breaker points (or other triggering device). The GREY wire is the tach wire and is only on the helm side of the harness. The connector is used to make the "splice" for this junction.

I made the changes as you described. DOnt know if it makes a difference but forgot to mention in my diagram the petronix electronic ignition kit i installed. I have now put that in there. Let me know if it works.

I apologize for just text. I wish I could diagram this.

It was almost like looking at a diagram! Thank you for taking the time and effort to help me out here. Done a lot of work on this boat and you guys have made it nothing but easier and have saved me a ton of money!

 

[Don S]

Re: Oil pressure Switch Wiring For Fuel Pump

You moved the wrong wire, hook it up like this one. Make a new purple wire from the OP switch to the purple wire in the wiring.

 

[shawnn82]

Re: Oil pressure Switch Wiring For Fuel Pump

You moved the wrong wire, hook it up like this one. Make a new purple wire from the OP switch to the purple wire in the wiring.

Done, Thanks Don. Here is the final drawing. Where i hooked up the purple wire is really the same place you referenced on the drawing, since on the drawing, that would be the place where the actual two connectors mate. Hence i was left with either the coil wire or alternator as both are really connected to the same place.
I only did this as a quick reference card should god forbid anything go wrong while im out at sea, i can troubleshoot easily. POsting it on here, maybe it will help someone in the future with a 1986 AQ131A and 275 Drive. Im off to start wiring!
BTW, what thread sealant would you recommend for attaching the OP sender + OP switch On a Tee adapter to Engine block?

 

[sqbtr]

Re: Oil pressure Switch Wiring For Fuel Pump

Good old thread tape.

 

[Don S]

Re: Oil pressure Switch Wiring For Fuel Pump

Not sure how I missed it before, but the power wire to the 30 terminal does not go directly to the battery, normally they come off the harness coming from the main engine circuit breaker. In your system, that is the 40A breaker above the battery.

DO NOT use teflon tape. any paste type pipe thread sealer will be fine. Teflon tape has no place on a boat.

 

[shawnn82]

Re: Oil pressure Switch Wiring For Fuel Pump

Not sure how I missed it before, but the power wire to the 30 terminal does not go directly to the battery, normally they come off the harness coming from the main engine circuit breaker. In your system, that is the 40A breaker.

Thanks, will wire the 30pin on fuel relay to the breaker. Will stay away from the teflon too!