Low fuel Pressure - Pump or regulator?? 7.4 MPI

NJMatt50

Member
Apr 28, 2009
225
Jersey Shore
Boat Info
2005 Sundancer 420. Sea lift platform, Axiom Pro, FLIR.
Engines
Cummins 480ce
I could not really rev the boat past 3000 without a whole lot of fwd stick. I narrowed my problem to 26# of fuel pressure at idle and did not go up revving at the dock. So how can I determine if the pump is bad or the regulator? Pulling the vacuum line did not change the pressure either. Thanks.
 
Try checking your fuel pressure with the engine off, but key in on position. Make sure it is up to spec. (39 Psi?) This takes the regulator out of the equation.

Tom
 
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Priming the engine with key on gives me 26# of pressure. I will be replacing the pump.
 
Seems like the year of the fuel pumps! At least you were able to get home with it still running and diagnose it. Mine just out-and-out failed...the engine would not re-start after we had reached our destination. It was a slow ride home on one engine...

Hopefully your's is easier to replace than mine was. Good luck!

Tom
 
Was not the fuel pump.. Waste of $ for that.. Now the regulator..
 
Did you try changing the fuel filter?

Did you look for a restriction in the intake line?

Clogged anti-siphon valve?

Doug
 
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The Mercruiser procedure for my engine to determine which is at fault is to restrict the fuel return line while watching the pressure. If it goes up (not to exceed 60 psi) it's the regulator. If not - the pump (providing you've ensured there are no blockages or restrictions in the fuel delivery system). I've used this procedure on my engine and it works. Hope this helps - Bob
 
Yes, it helps but too late already replaced the pump. I replaced the regulator, problem resolved. Thanks.
 

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