Merc 4.3 fuel pump or oil switch

[DivrDown]

I have 1996 Crownline with the Merc 4.3 carbed with electric fuel pump.

It will start right up and run fine until the fuel runs out of the carb then it stalls and will not start. If I unplug the fuel pump with the key on and plug it back in I can hear it run for a few seconds then quit. After doing this a few times the boat will start and run fine for the rest of the day stop and start several times.
I know there is the wire (purple/black) running from the oil pressure switch to the realy fuel pump. Is there a way to bypass the switch to check to see if the fuel pump is bad or the switch. I had this issue last year and I rebuilt the carb It has good oil pressure by the gauge and also with a seperate gauge there is good oil presssure
thanks

 

[Bt Doctur]

Re: Merc 4.3 fuel pump or oil switch

The oil pressure sender for the gauge is completely different.
There is a oil pressure switch just above the oil filter that is for the fuel pump.

 

[Jimmy627]

Re: Merc 4.3 fuel pump or oil switch

Hey Bt Doctur, are these oil pressure switches knowned to go bad ?

 

[Maclin]

Re: Merc 4.3 fuel pump or oil switch

If you do a search on this board you will find a lot of posts regarding inoperative oil pressure safety switches.

 

[Don S]

Re: Merc 4.3 fuel pump or oil switch

Is there a way to bypass the switch to check to see if the fuel pump is bad or the switch.

Not sure about your purple/black wire. Below is the wiring diagram. If you jumper the two wires on the oil pressure switch and it keeps running, you need a pressure switch.
The reason it keeps running for a few seconds after you restart it, is because the fuel pump gets power from the starter solenoid not the oil pressure switch.

 

[DivrDown]

Re: Merc 4.3 fuel pump or oil switch

OK That helps alot. Next question can anyone post a picture of the 2 sensors and their location on the motor. I may have an issue with the 2 oil switches pressure unit being installed wrong.

 

[DivrDown]

Re: Merc 4.3 fuel pump or oil switch

Ok so I beleive that I need to order the oil presuure switch. Who has them? Searching the net and I am not haveing very good luck. I am not close to any dealers so I need to order online. thanks