fuel issue 350 mpi

[wags23]

i have had a mess going on . THE fabricater of my new tank used silicone on my sending unit and clumps were clogging my pickup. boat kept shutting down at wot . my fuel pump got jammed with silicone and sounded like it was cavitating and was only gettin 20 lbs at the rail . replaced fuel pump and checked lines going back to the tank .now its getting 25 lbs at the rail its a1998 . manual says 34-38 .

 

[wags23]

Re: fuel issue 350 mpi

anyone know what the fuel pressure should be at the rail running on muffs.

 

[Fun Times]

Re: fuel issue 350 mpi

i have had a mess going on . THE fabricater of my new tank used silicone on my sending unit and clumps were clogging my pickup. boat kept shutting down at wot . my fuel pump got jammed with silicone and sounded like it was cavitating and was only gettin 20 lbs at the rail . replaced fuel pump and checked lines going back to the tank .now its getting 25 lbs at the rail its a1998 . manual says 34-38 .

It's hard to tell they have a few numbers. What manual do you have?

 

[wags23]

Re: fuel issue 350 mpi

in one place it asks if your getting 25lbs at the rail . but it says in the specs 34-38.seloc

 

[Zackman]

Re: fuel issue 350 mpi

Per the Merc Manual...​

When the ignition is turned ON, the Engine Control Module (ECM) will turn the fuel pump ON for 2 seconds. ​

During engine cranking, the ECM will turn ON the fuel pump. It will remain
ON as long as the engine is cranking or running, and the ECM is receiving ignition reference pulses. If there are no reference pulses, the ECM will shut OFF the fuel pump.​

The pump will deliver fuel to the fuel rail and injectors, then to the pressure regulator, where the system pressure is controlled to approximately:​

TBI Models:
28-32 psi (193-221 kPa)​

MPI Models:
34-38 psi (234-262 kPa).​

Excess fuel is then returned to the water separating fuel filter.

The 25 psi is when you first turn the key on, you should be recieving at least this much fuel pressure, not when it's running.​

 

[wags23]

Re: fuel issue 350 mpi

fuel pressure regulater was replaced and the fuel pump .cleared pickup and lines leading to the pump are cleared. what could be causing the pressure to not be at 34-38 when running?

 

[Fun Times]

Re: fuel issue 350 mpi

fuel pressure regulater was replaced and the fuel pump .cleared pickup and lines leading to the pump are cleared. what could be causing the pressure to not be at 34-38 when running?

You might have a fuel anti siphon valve cloged up, This is the fitting that is mounted to the fuel tank and the fitting where you hook the fuel line up to, That fitting has a spring ball valve on the inside of it, And it might be cloged up also with silcone. Another test you could do is by pass the boat tank and hook up A fuel line to the engines hose barb fitting and get a small gas can and put the hose in the gas can and then try to key it up and then start it up to see what fuel pressure you are now getting by by passing the boats fuel tank.

 

[wags23]

Re: fuel issue 350 mpi

i ran it on a temp tank and ran good originally than cleaned pickup thats where we found the silicone first. silicone got past fuel filter and into fuel pump replaced fuel pump boat runs great now but on the fuel pressure check it only shows 25 -30 lbs when running .

 

[Fun Times]

Re: fuel issue 350 mpi

i ran it on a temp tank and ran good originally than cleaned pickup thats where we found the silicone first. silicone got past fuel filter and into fuel pump replaced fuel pump boat runs great now but on the fuel pressure check it only shows 25 -30 lbs when running .

Have you tryd unhooking the vacuum line to the fuel regulator yet to see if the psi goes up with the engine running the hole time?

 

[wags23]

Re: fuel issue 350 mpi

yes and it goes up. is that the true fuel pressure? thanks johnny

 

[Fun Times]

Re: fuel issue 350 mpi

yes and it goes up. is that the true fuel pressure? thanks johnny

Should be as long as every thing is working right and it gose up to with in specks. What 2 #s do you get with it hooked up and unhooked with it running?

 

[wags23]

Re: fuel issue 350 mpi

25 lbs hooked low 30s running

 

[Fun Times]

Re: fuel issue 350 mpi

25 lbs hooked low 30s running

You might have a bad gauge also so you might be right there with in specks. Just a thought.

 

[wags23]

Re: fuel issue 350 mpi

its a snapon fairly new . read 43 lbs on my friends 2003 mpi will check thanks for your help . johnny