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-   -   502 MPI Low Fuel Pressure (https://www.offshoreonly.com/forums/general-q/339958-502-mpi-low-fuel-pressure.html)

SB 08-20-2016 06:27 PM

What did you tell the marina today that worked on your boat, charged you a ton of money, and by your first drive reported results fixed nothing ?

camptappakeg69 08-21-2016 08:59 AM

Best thing I have ever done to my boat was take all of that crap fuel system out, replace it with electric fuel pump and pressure regulator.

camptappakeg69 08-21-2016 09:58 AM

https://m.youtube.com/watch?v=1eDUf_EHcEo excuse the loud flappers, freaked me out at first!

Nick616 08-22-2016 06:32 AM


Originally Posted by SB (Post 4473189)
What did you tell the marina today that worked on your boat, charged you a ton of money, and by your first drive reported results fixed nothing ?

I think they treated me fairly - was actually less than I was expecting. The work they did was needed, we just haven't figured out all the fuel system issues . . .


Originally Posted by camptappakeg69 (Post 4473293)
Best thing I have ever done to my boat was take all of that crap fuel system out, replace it with electric fuel pump and pressure regulator.

In hind sight, I probably should have just done this, but I'm trying to keep it relatively "stock" so I don't scare away any prospective buyers in the future when I sell it to upgrade . .

Nick616 08-23-2016 07:52 AM

So I did a double check on fuel pressure - pressure pumps up to about 32psi when the pump first turns on - pretty much holds there. I don't know why an OEM pressure regulator would not hold the 36-38 recommended for this fuel system.

Is there an easy "temporary fix" to get the pressure reliably up? I thought about adding a second pressure regulator on the return line from the cool fuel pressure relief - but I am concerned that the OEM pressure relief won't handle the 36psi on the discharge - I don't want to blow it apart when on the water . .

Would this be ok or a bad idea? If a bad idea, is there an adapter I can put in place of the OEM pressure relief to add an aftermarket relief down stream? ( I don't really want to re-do the entire fuel system if it can be avoided )

camptappakeg69 08-23-2016 02:10 PM

Maybe because someone retrofitted a cool fuel system to a vst system is the source of the fuel pressure problem. Do both systems have the pressure regulator in the same spot ( on the front of the fuel rail for the vst). Does the cool fuel use a mech pump?

Nick616 08-23-2016 02:16 PM

I'm sure it was VST origninally and has been retrofitted to cool fuel. The pressure relief is on the top of the fuel cooler. I'm not sure what happened to the VST pressure relief - it is no longer there. ( There is a "damper?" with a clear tubing connection to one of the intake ports )
Cool fuel does not use a mechanical pump by design, but mine has one on it - I'm guessing that was done to attempt to solve the vapor lock problem, but I have no idea why it is there.

camptappakeg69 08-24-2016 12:04 PM

Sticking with my original thought, get rid of that mess and replace it with a pump and regulator. Your set up is not "stock". Properly done, changing it over will not hurt value and will perform better and last longer in my opinion.

Nick616 08-24-2016 12:32 PM


Originally Posted by camptappakeg69 (Post 4474566)
Your set up is not "stock".

That's a good point :)

I have looked at other threads on this issue - and it is a little overwhelming :)

Is there a good "how to" some place with recommended components?

Can I use a fixed pressure regulator or do I need something that will adjust like this: Aeromotive Marine Fuel Pressure Regulator

Where do people get the fittings and braided hose assemblies - online or should they be available at a local hydraulic hose shop? ( Did some googling and found the answer to this - I'm more used to working with hydrauilc hoses that are crimped on fittings, but also have to withstand 2000 psi )

camptappakeg69 08-25-2016 12:01 PM

Got most of my components on ebay, some stuff at jegs, made my own lines with an fittings.


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