Fuel Issue on my 6.2L MX MPI Inboard

[w317chester]

Okay so i'm almost there with my newly remanufactured 6.2L MX MPI (serial number OM317417) engine but i've got a fuel issue. So my first fuel issue was my fuel pressure was too high. The engine would idle fine but if you gave it throttle it would want to die (guess it was running too rich and flooding the engine). We measured the fuel pressure and it was approximately 80-90 psi and then we replaced one of the fuel pressure regulators (the one down on the cool fuel cooler and next to the fuel pump). After we replaced that regulator now my fuel pressure is too low (engine want stay crunk). Fuel pressure is around 10-20 psi. My fuel pressure should be 43 psi.

Some things i've done/some thoughts:

1. I have brand new water separating fuel filter
2. I have brand new in line fuel filter
3. I siphoned all (or at least as far as the gas pickup could siphon) old gas out of my tank and replaced with fresh gas
4. Both fuel pumps are running (yes there are two: one coming from the gas tank and then the one next to the cool fuel system that delivers fuel to the fuel rail)

Any help is much appreciated!

 

[alldodge]

Either your new regulator or fuel pump is bad or the something isn't connected correctly. Below is how your fuel system should be hooked up. The regulator sends excessive pressure back to the fuel filter, so with only 10-20 psi either the fuel pump has gone out or the regulator is sending all the fuel back

 

[w317chester]

Either your new regulator or fuel pump is bad or the something isn't connected correctly. Below is how your fuel system should be hooked up. The regulator sends excessive pressure back to the fuel filter, so with only 10-20 psi either the fuel pump has gone out or the regulator is sending all the fuel back

Thanks Alldodge. The picture didn't attach. I don't think it's the fuel pumps though because they were supplying too much fuel pressure before I put on a new regulator. I agree with you about perhaps the regulator is sending all the fuel back to the water-separating fuel filter but just can't under stand why this would be?

 

[alldodge]

The iboats data base is sure working weird again. I see the pic, I see the pic in your quote of my statement, but you cannot see it. :facepalm:

Does the fuel pump run constantly or just for the few seconds then shut off? If it shuts off does it turn back on while cranking?

 

[w317chester]

The iboats data base is sure working weird again. I see the pic, I see the pic in your quote of my statement, but you cannot see it. :facepalm:

Does the fuel pump run constantly or just for the few seconds then shut off? If it shuts off does it turn back on while cranking?

I think it constantly runs when the I turn the key to the on position but not trying to crank the engine. I'm pretty sure this is what it does but i'd have to check.

 

[w317chester]

The iboats data base is sure working weird again. I see the pic, I see the pic in your quote of my statement, but you cannot see it. :facepalm:

Does the fuel pump run constantly or just for the few seconds then shut off? If it shuts off does it turn back on while cranking?

No I was wrong, the fuel pump runs for a few seconds and the quits when the key is turned on.

 

[alldodge]

No I was wrong, the fuel pump runs for a few seconds and the quits when the key is turned on.

Guess the pressure your seeing is just the residual from the pump coming on at first key.

Before we go complicated how about starting with the easy stuff. Connect the fuel pressure gauge to the Schrader valve and turn key on. Pressure should build to 35psi minimum gauge should not drop immediately to zero. If it doesn't turn off and try again a few times. Also note that if the fuel line has air in it, the air needs to be bleed out

 

[w317chester]

Guess the pressure your seeing is just the residual from the pump coming on at first key.

Before we go complicated how about starting with the easy stuff. Connect the fuel pressure gauge to the Schrader valve and turn key on. Pressure should build to 35psi minimum gauge should not drop immediately to zero. If it doesn't turn off and try again a few times. Also note that if the fuel line has air in it, the air needs to be bleed out

Thanks for the tip Alldodge. I'll attempt this and make sure all of the air is bled out but I think I attempted this last night. What would be your next step if i'm unable to achieve pressure this high?