Electric fuel pump

[Sugo]

I installed an electric fuel pump on my 94 4.3L Mercruiser. I installed a oil pressure switch on the power feed to the pump. Do I need to run parallel wires to the dash to a spring loaded switch to prime the motor before oil pressure occurs or can I use the choke wire somehow. Or is this necessary? IF so could someone provide some type of wiring diagram for this application
Thanks for any help.

 

[eclipse196]

Re: Electric fuel pump

I did that replacement on my 92 4.3 and did install a momentary switch to allow for priming before the engine cranks. I read several discussions that recommended that arrangement. Only used it once before I tore the boat down for stringer and floor replacement. Wish I could be of more help.

 

[Pete104]

Re: Electric fuel pump

Weren't you already set up with an "electric pump"?
You can engineer anything you want.

 

[Don S]

Re: Electric fuel pump

I installed an electric fuel pump on my 94 4.3L Mercruiser. I installed a oil pressure switch on the power feed to the pump. Do I need to run parallel wires to the dash to a spring loaded switch to prime the motor before oil pressure occurs or can I use the choke wire somehow. Or is this necessary? IF so could someone provide some type of wiring diagram for this application
Thanks for any help.

No, you do not need a primer or extra wiring. The starter powers the fuel pump when the engine is cranking.. Mechanical pumps didn't need constant priming of the carb to start.

Here is Mercs wiring for the electric fuel pumps.

 

[Sugo]

Re: Electric fuel pump

One question about the wiring. I assume when the key is in the starting position there is power to the PUR/YEL wire. So when the oil pressure switch opens would this keep power to the PUR/YEL wire after the key is in the "on" position as well? Would this effect the choke? or under normal operating conditions would the PUR/YEL wire to the choke have constant power to keep it open anyway?

 

[Don S]

Re: Electric fuel pump

Yes, the Purple Yellow wire will have power on it after the pressure switch closes. And yes, it puts power on the choke, just like it should. Although the power also goes to the starter solenoid, it only goes to the terminal which is not connected to anything when the key is in the run postion.

 

[Sugo]

Re: Electric fuel pump

I now understand, thanks for the education

 

[Sugo]

Re: Electric fuel pump

One last question, If I am going to add an in-line fuse for the electric fuel pump what amp fuse would do the job and where would be the best spot in the line to put it?

 

[Don S]

Re: Electric fuel pump

Merc doesn't use a separate fuse for the fuel pump on carbed engines since it's all through the purple wire. There is a 20A fuse for power to the ignition switch, which will cover the pump as well.

 

[Sugo]

Re: Electric fuel pump

Thanks again