electric fuel pump question

[ahhhhchoooo]

merc, elect. fuel pump carbed. 5.7L
what causes the fuel pump to turn on for a second when you turn the ignition on but turn off after about a second of running. I know it shuts off because of no oil pressure at the oil pressure switch but how does the fuel pump get the voltage to begin with? I am not having a problem with the boat but am curious.

 

[lime4x4]

Re: electric fuel pump question

more then likey if it's factory install it uses a relay for the fuel pump.The pump is energized briefly when you turn the key then the oil pressure switch takes over

 

[Don S]

Re: electric fuel pump question

more then likey if it's factory install it uses a relay for the fuel pump.

Sorry, but that is not how it works. Power is applied to the fuel pump from the starter solenoid. When the starter is cranking the engine, power from the outside small terminal applies power to the fuel pump before the oil pressure switch. When you let off the ignition, the pump stops. But there is enough gas in the carb at that point to run the engine for about 20 seconds if the OP switch doesn't work.