Mechanical to electric fuel pump wiring

[a1nowell]

I am going to install an electric fuel pump on my M/C 470 and need some difinitive wiring instructions. I have bought a 3 leg oil sending unit but I cannot figure out where to wire the existing wire to the dash pressure guage.

 

[Bondo]

Ayuh,.... Donno what ya bought, But,.....
An oil pressure sender tells the gauge what to show,....
Ya need an oil pressure Switch, to wire the fuel pump through, so the fuel pump can't/ won't run unless the motor is Runnin',.....

To power the fuel pump, only when crankin' the motor on the starter, run another wire from the outside tiny terminal on the starter's solenoid, directly to the fuel pump,....
Once the motor starts, the ignition power through the oil pressure switch will take over,...

 

[bruceb58]

You need a pressure switch in addition to the current sender you have.

 

[a1nowell]

I have bought an Airtex pump and a 3 pronged pressure switch recommended by Airtex.

 

[Scott Danforth]

here are instructions https://static.summitracing.com/global/images/instructions/sum-g1438.pdf

 

[a1nowell]

Thanks Scott

 

[a1nowell]

OK fellas I still need a little help in hooking this up. First of all this 470 engine is down in a deep dog house in the rear of my middle toon. I cannot even see the starter solenoid. I am thinking of splicing into the starter ignition (start) and ignition (run) wires after they come off the big circuit breaker in the wiring harness. But before I start splicing into wires I want to know I have the right ones. I have Mercury Manual #8 and although it gives me the wiring diagrams it does not specifically say where each wire goes. I believe the starter ignition (start) wire is the yellow/red and the power wire for the run position is the red/purple. Any help would be appreciated.

Thanks, Larry

 

[Bondo]

First of all this 470 engine is down in a deep dog house in the rear of my middle toon. I cannot even see the starter solenoid.

Ayuh,.... What are ya gonna do when the starter needs to be replaced,..??

The red/yellow wires are the starter exciter circuit,...
The purple/ red are the wires powered when the solenoid is engaged,...
The purple wires are the ignition/ run circuit,....

 

[a1nowell]

Thanks Bondo

 

[a1nowell]

Bondo,
I just want to comfirm:

​1) Yellow/red (not red/yellow) to the Starter post of the Oil Pressure Switch?

​2) Purple to the run post of the Oil Pressure Switch?

 

[Bt Doctur]

post a pic of your starter and solenoid.Dont know what post your calling what.
On the pressure switch there are 3 pins C= common this goes to the fuel pump positive wire, NO= this is normally open and closes when it sees oil pressure this is where the switched 12v power goes. NC = goes open when it sees oil pressure ,this is the wire from the "I" post of the starters solenoid. .
Depending on what solenoid you have now will determine where you get this connection from , you MAY be able to use the yellow/red that goes to the starter solenoid

 

[Bt Doctur]

one post will have the yellow/red wire ,you use the other post to the pressure switch pin that is NC

 

[Bt Doctur]

 

[a1nowell]

Bt Doctor
​As said in the 5th post up I can't even see the starter solenoid that is why I am considering splicing in to the wire of the wiring harness after the 50 amp breaker. My Oil Pressure Switch is an Airtex OS75 post are marked: P to pump, S to the starter solenoid and I to the ignition.

 

[Bt Doctur]

here are instructions https://static.summitracing.com/glob.../sum-g1438.pdf

Better let then know the motor wont run with the wires going to the neg side of the coil for a fuel pump activation method. They are showing a low/no oil pressure cutoff in that diagram.

 

[Bt Doctur]

the switched 12v can be taken from the electric choke lead to go to the "I" post and , try using the yellow/red from the slave to go to the "S" post or the purple/yellow at the coil

 

[a1nowell]

I am not using the Summit diagram. I am using the diagram that came with the OS75,: S to starter, I to ignition(run), P to pump

 

[Bt Doctur]

 

[a1nowell]

I'm not using the Summit diagram, I'm using the one that came with the OS75: S to starter. I to ignition( run) and P to pump.

 

[a1nowell]

I have that wiring diagram I am trying to confirm splicing into yellow /red to Starter post and The purple to the Ignition post.