525 electric fuel pump help
 

Has anyone had experience with a HP 525 electric fuel pump that won't shut off ??? We headed to the lake today and after a short run I shut down the engine and noticed the electric fuel pump still running with the ignition key off. Turning the batteries off stops the pump. The pump will stay off when turning the batteries back on, however, as soon as I turn the ignition switch to the on position the pumps starts running again and won't shut off until the battery switch is turned off. Help!:angry-smiley-055: :angry-smiley-055:

Happened to me 3 months ago... You need a new ECM $1600.00

I had a friend and certified merc mechanic check everything. Also merc technical line said it has been a common problem. They actually sent me the ECM for free. I was pretty impressed with that because I was just out of warranty. Happened at 50 hours.

Electrical gremlins
 

When you key on the ECM gets power and sends power (connects the ground to the fuel pump relay) to the electric fuel pump for a short period of time and if the engine is not started the fuel pump relay will be commanded by the ECM to shut off the pump. Sounds like you might want to make sure the fuel pump relay is not going bad a sticking on. If the shut off (ground signal) from the ECM is not opening up on key off then the ECM could be bad, but the fuel pump should still go off because your main power relay should be opening and turning off all power to the pumps and ECM? Looks like you've got to do some electrical "sherlock Homes" here with a meter, a manual with wiring diagram and a scan tool might be helpful. Good Luck, be careful, be patient.

Regards,
Ray @ Raylar

Fuel pump issues
 

Thanks for the suggestions. I did try swapping out the relay. That didn't work. The dealer has contacted Merc Racing and they believe the PCM is bad. We will give the PCM a try next. I wish I had a wiring diagram!!