Mercruiser fuel pump buzzing

[bmontymi]

Our 2003 4.3 Mercruiser Bravo sterndrive fuel pump continues to buzz after the boat is turned off. The only way to stop the noise is to disconnect the battery. Is there any way to fix this problem?? Can't even get your hands on the pump. 3/4 of the gas is new and the filter has been changed . Thanks,



Problem has been solved - Faulty Fuel Pump Relay Switch. Thank you everyone!!!

 

[Haut Medoc]

Re: Mercruiser fuel pump buzzing

Welcome to iboats......
Is this a new problem?
My guess is that the oil pressure switch is stuck in the closed position or has been bypassed.....
It should be located under the #7 plug wire......
With the key off, there should be no continuity across this switch.....
http://forums.iboats.com/showthread.php?t=192022
The link above will show you the wiring system, it is getting power with the key off somehow.....
Pic courtesy of Don S......​

 

[Don S]

Re: Mercruiser fuel pump buzzing

You have an electrical problem, not a fuel problem or filter problem. Is this a carbed or MPI engine?
Do you have an engine SN handy?

 

[Don S]

Re: Mercruiser fuel pump buzzing

Has any work been done on the starter, or battery cables going to the starter?
I have seen the main battery that attaches to terminal A in the drawing be bent over and touch terminal D. This will cause the fuel pump to run.

 

[newport dave]

Re: Mercruiser fuel pump buzzing

I've seen these exact symptoms on a couple of late model Mercruiser MPI engines. In those cases it was a stuck fuel pump relay.

Dave

 

[bmontymi]

Re: Mercruiser fuel pump buzzing

Thank you Dave! It was the Fuel Pump relay switch. Problem solved.