Electric Fuel pump conversion

[Jonezin1]

I
I have a 93 marine power 350 sports pac carbarted

I made the manual fuel pump conversion to electric.
I'm running carter's low psi pumps 6-8 psi
I've installed a 3 prong oil pressure safety switch.
I'm running a 40amp relay

On the pressure switch they are labeled
P
S
I
S being the connection that comes from the starter yellow/red wire.

Here's my question,
Should the "S" wire (yellow/Red) be contently hot with key in the on position?

My problem is, when I turn the key to on to prime, pump doesn't run
Pump is new if i supply 12 volts independently it works. Im going to attach my wiring diagram. Please advise if its wrong

 

[flashback]

This thread may help..

Wiring In Electric Fuel Pump

Hi everyone, I'm trying to incorporate an electric fuel pump into a 5.7 Mercruiser. The prior engine (5.0) had a mechanical fuel pump but the replacement engine does not have all of the holes for the mechanical fuel pump built into the block. Some notes: 1) The replacement engine is on an...

forums.iboats.com

It helped me a bunch last fall,,,

 

[Bondo]

My problem is, when I turn the key to on to prime, pump doesn't run

Ayuh,...... Welcome Aboard,..... Carbed motors don't do that,.....
The fuel pump should only be powered when crankin' the motor on the starter, 'n when there's oil pressure,....

 

[Scott Danforth]

why did you change the mechanical fuel pump for a problematic electric fuel pump?

 

[Lou C]

Exactly! Mechanical pumps are long lived and basically trouble free!
The S wire (start) on the solenoid (yellow/red) does not get power when you turn the ignition on, it only gets power when you turn the key to start. That should work for you because by the time the engine starts (when you release the key the S terminal no longer gets power) the oil pressure should have increased enough to close the oil pressure switch to power the pump.

 

[Jonezin1]

Ayuh,...... Welcome Aboard,..... Carbed motors don't do that,.....
The fuel pump should only be powered when crankin' the motor on the starter, 'n when there's oil pressure,....

So my wiring is correct?

 

[Jonezin1]

why did you change the mechanical fuel pump for a problematic electric fuel pump?

Takes forever to get fuel, i replaced the mechanical pumps last year. I want to crank and go not sit wishing and praying.

 

[Jonezin1]

So my wiring is correct?

Thanks I'm actually old here just been awhile since I've posted

 

[Lou C]

If you don’t get quick starts with a mechanical pump there is likely another problem. Unless you are starting an engine not run in months because then yes the fuel in the bowl can evaporate. The first start of the season my boat takes 3 crank overs to start (mechanical pump, Quadrajet carb), but when being used regularly it starts right up.

 

[Scott Danforth]

Takes forever to get fuel, i replaced the mechanical pumps last year. I want to crank and go not sit wishing and praying.

you either have a leaking carb bowl (rochestors are known for this) or you have another issue like the engine sitting for more than 6 months and the fuel has long evaporated .

 

[Silvertip]

If you had a starter solenoid with an "R" terminal that would serve the same function as a separate "prime" switch that feeds power to the pump prior to starting. The "R" terminal used to be used for a ballast resistor connection on old ignition system vehicles but electronics have eliminated the need for it. When the key is turned to start the "R" terminal would bypass the pressure switch until the engine started. The system would then work as your diagram shows. Unfortunately your engine will not start until oil pressure is built up and the switch closes to power the pump which then has to prime the system.