Mercruiser 5.0 MPI Bravo 3, has low fuel pressure, doesn't maintain pressure

[Mouseketeer53]

Searay 2005 Sundeck Serial Number OW063935. We have replaced the cool fuel module and the sea water pump, both are now new. When we put a gauge on the fuel rail we have 5 lbs of pressure. If we put a bulb on it and pump up pressure, it will run but slowly goes down and dies. Stumped!! Any suggestions? There is fuel in the line. Been working at this for three weeks and buying parts. Today replaced all the o-rings in the lines. Still haven't solved the problem.

 

[Bt Doctur]

MPI needs 42 psi. TBI is atleast 38 psi..
Remove the fuel line from the fuel sep, install a remote tank and retest the pressure.You say you replaced the module, the complete whole unit or just the pump? ser# shows it a the cool fuel III mounted on the stbd side
3-7 psi is a low pressure pump for carb applications
If the fuel pressure is there on a remote tank than look at the anti-syphon valve

 

[Fun Times]

Also being a Sea Ray, you'll want to see if you have the parker fuel solenoid valve installed on the boat side as it can be problematic at times.... http://clubsearay.com/showthread.ph...l-Solenoid-Manual-Overide?p=265352#post265352

 

[Mouseketeer53]

The first thing we replaced was the fuel solenoid valve as it was too hot to touch and we thought that was it. We replaced the whole module, not just the pump. Then put new o rings on everything thinking it was an o ring problem. The line that powers the pump is getting fuel. When we bypass the system and run power directly to the pump, it works fine. When we check the voltage path to the pump when you turn the key on, it gets 12 volts and then immediately fades back to zero.

 

[Fun Times]

When we check the voltage path to the pump when you turn the key on, it gets 12 volts and then immediately fades back to zero.

And does the 12v come back up once you start cranking the engine over to start?

 

[Mouseketeer53]

Yes the 12 volt come back up when cranking.

 

[Challenger84]

I've had a very similar problem I was able to fix.
Have you checked / replaced your fuel filter?
Make sure when you do change out the Fuel filter that you fill up the filter with fuel first before reinstalling it.

I've linked to my POST on my issue and what i did to fix it..
I've taken my boat out at least 10 times since.

http://forums.iboats.com/forum/engi...fuel-gen-ii-fixed-issue-fuel-pump-replacement


I hope this helps you with your issue..