Question regarding wiring up a carter electric fuel pump

[findinghomer]

I am building my wiring harness for my new engine so I've been doing a lot of research and studying the proper way to do this here on the forums, what I'm not quite understanding is it all ties in to the keyed purple ignition wire From the main harness, But the fuel pump power also connects to the D terminal of the starter, to supply its power while cranking. So wouldn't that supply 12 volt to the D terminal anytime the key is in the on position? Even when I let go of the key from cranking? Just want to make sure I get this right before I tape everything up

I've included a schematic of how I'm thinking it's wired, ( i included a relay so the pump is powered from the 12-volt breaker rather than the oil pressure switch) . But other than that this is how I'm understanding it.


Btw, yes I got a tee fitting

 

[Chris1956]

Gee, I also think your wiring will provide power to the starter solenoid whenever the key is on.

You might grab a wiring diagram from a late model MerCruiser and see how they did it. That should be avail on the web.

 

[Chris1956]

That is a marine-rated fuel pump, right?

 

[findinghomer]

Gee, I also think your wiring will provide power to the starter solenoid whenever the key is on.

You might grab a wiring diagram from a late model MerCruiser and see how they did it. That should be avail on the web.

Lol. Yeah didn't to look right to me, but this is a diagram that I was going by, and it looks like they're tying the purple wire into everything, But I think I'm just not understanding the diagram, But that's why I'm here I haven't done anything yet, And doesn't seem right

 

[findinghomer]

Right here in particular, where the power to the pump is connecting to the starter and also the ignition wire, or what is that little ring represent that's circled?

 

[findinghomer]

That is a marine-rated fuel pump, right?

It's a jegs Carter style Marine fuel pump.

 

[Scott Danforth]

This is how I have the carter wired in my boat. (however double check the oil pressure switch terminals for the one you use)

 

[findinghomer]

This is how I have the carter wired in my boat. (however double check the oil pressure switch terminals for the one you use)

D

My oil pressure switch only has two leads on it.
So basically I just need a relay on each side of my oil pressure switch, One that will allow me to pull power from starter while cranking, and then deactivate it when I'm no longer cranking , and pull power from my source?

 

[Scott Danforth]

Thats how the circuit I use works. it also works as a starter interlock preventing cranking once the engine is running.

 

[nola mike]

The factory wiring doesn't use a relay. You're correct that the starter is back fed once the engine is running, but that connection opens when OP decreases at the switch. I used a 3 contact OP switch. Switch closes with power from the starter (or I used the yel/red wire from the ignition/slave solenoid) and powers relay at 85, closing 30 (12v battery) and 87 (to fuel pump). When there's sufficient OP, OP switch closes, and power through the switch is provided by the purple wire (connected to 3rd terminal of switch) instead of the starter.

Your 2 pole switch will work if you wire 86 to the starter (or yel/red) and 1 side of the OP switch. Other side of the switch goes to purple. 30 gets 12v, and 87 goes to fuel pump.

 

[findinghomer]

The factory wiring doesn't use a relay. You're correct that the starter is back fed once the engine is running, but that connection opens when OP decreases at the switch. I used a 3 contact OP switch. Switch closes with power from the starter (or I used the yel/red wire from the ignition/slave solenoid) and powers relay at 85, closing 30 (12v battery) and 87 (to fuel pump). When there's sufficient OP, OP switch closes, and power through the switch is provided by the purple wire (connected to 3rd terminal of switch) instead of the starter.

Your 2 pole switch will work if you wire 86 to the starter (or yel/red) and 1 side of the OP switch. Other side of the switch goes to purple. 30 gets 12v, and 87 goes to fuel pump.

Ok thank you, And then ground 85?

 

[nola mike]

Ok thank you, And then ground 85?

yes

 

[findinghomer]

yes

Thanks Mike! This has been the biggest headache of my engine swap.

 

[Chris1956]

Let me ask a dumb question. Why do you need an electric fuel pump? They were used on late model carbs and fuel injection. They were needed on FI, but not essential on carb motors.

 

[nola mike]

Let me ask a dumb question. Why do you need an electric fuel pump? They were used on late model carbs and fuel injection. They were needed on FI, but not essential on carb motors.

From mid '90's on or so the V6/V8s didn't have the machining for a mechanical pump.

 

[JustJason]

It may help understand how to wire the fuel pump if you understand why it's wired the way it is.

The fuel pump should receive power only under 2 conditions.

1. When the engine is actively cranking over, but has not yet started. In this condition, the fuel pump gets power from the bypass terminal on the starter solenoid.

2. When the engine has sufficient oil pressure to close the oil pressure switch. Under this condition, when there is no oil pressure, the oil pressure switch is open, and not sending power to the pump. When there is sufficient oil pressure, the switch closes and sends power to the fuel pump.

And that's it, under no other condition should the fuel pump be receiving power.

 

[Chris1956]

From mid '90's on or so the V6/V8s didn't have the machining for a mechanical pump.

OK, let me ask a dumber question. If his motor does not have the machining for a mechanical fuel pump, why does it not have the wiring for an electric fuel pump?

 

[nola mike]

OK, let me ask a dumber question. If his motor does not have the machining for a mechanical fuel pump, why does it not have the wiring for an electric fuel pump?

OP hasn't let us know what he's doing but my guess is replacing long block with a newer one. His old setup had a mechanical pump.

 

[Lou C]

From what I was able to determine, the last use of the mechanical fuel pump was on the 4.3 V6 blocks made from 1987-1992, from '93 on up there was no machined mount for the mechanical pump. I'm not sure if it disappeared from the V8 blocks the same year or later.

 

[flashback]

My 95 v8 had a mechanical pump until a few years ago when it started puking and I then installed electric.