Electric fuel pump continues to run

2002 merc 5.0 MPI. This thing is crazy. Get to the sandbar and shut off the engine. After playing around & having a few ice cold beverages I heard what I thought was my blower running. I lifted the rear hatch and found that my electric fuel pump was running. I got it to quit by unplugging the fuel pump relay. So I go buy a new relay and put on. Fuel pump worked as it should. Cycled with key on then quit. Went out next day and the same thing happened (I turned the boat off with the key but the pump kept running). This time I just unplugged the relay (to kill the power to the pump) then I plugged the relay back in and the pump wouldnt run until the key was turned on (as it should). What would cause this!! By unplugging the pump relay its like it resets something and it will function properly after being plugged back in. I dont have a wiring schematic to see what else controls or is controlled by this relay. There has got to be other things because the relay has five terminals on it. Any ideas???

Re: Electric fuel pump continues to run

Five terminals is standard for a relay
1. Common
2. Normally Open
3. Normally Closed
4&5. power for the coil

When the pump continues to run after the key is off, do you still have power to the coil. If so, the problem is from there back. If not, the problem is another bad coil - it is sticking.

Re: Electric fuel pump continues to run

Yesterday I went out with my multi-tester and began checking wires for proper grounds and so forth. I was not able to accomplish anything though because the motor would not do it. It seems it only does it after it has been run for a few hours and it gets good and warm. Then it does it most of time that it is shut off but not every time. I cannot get it to stick on by hooking muffs up and letting it get to operating temp. and then shutting it off. Of course I didn't have my tester with me on the water when it happened but i will next time. I will check. Thanks