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Loss of fuel pressure 5.7 Vortec MPI

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    #31
    Have you tried swapping fuel lines between the motors? You may need to fabricate some special hoses if they do not reach. That would isolate the issue to either the fuel side or the motor side.
    Currently watching from shore while deciding what my next boat will be !

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      #32
      Sect 5 PFI Diagnosis (1).pdf
      Take a look at page 5-30 you might be onto something with the hall effect sensor I tried to up load the pdf it that dosen't work here is a link.

      https://www.google.com/url?sa=t&sour...Sf12Z3syX8ERJg
      1992 2452
      5.0 alpha1 gen2

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        #33
        Hopefully have a scan tool available on Wednesday.
        Problem has been finding someone with the correct Data Link Cable to enable the scan tool.
        Thanks for the link,I have been all over this circuit but need that scan tool so bad to pinpoint the source of the problem.
        I have not been able to obtain much info on the Ignition module on the Marine Power motor or the symptoms a bad module induces, but it is a Hall Sensor type module.

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          #34
          So the technician didn't have the correct cable to connect into the system and he had plenty of cables, said he had never seen this type of configuration before so back to the drawing board.
          His comment was to change the temp sensor and see what happens. Unfortunately I had already swapped it over from the other motor with no fix.
          Time to go back to basics.
          The fault is loss of fuel pressure after 8 minutes of running above 2200 rpm.
          I was convinced the fault was triggered by a sensor or other electrical based fault. But found no issues with it.
          It was time to get into all aspects of the fuel delivery system.
          I removed all components up to the fuel rail and pulled everything to pieces.
          I had concerns that the low pressure pump was where the fault lay however it bench tested fine, including checking the cooling coil around the pump was clear for the water to pass through. All good here..
          Then it was time to strip the H.P. fuel pump and inspect all components individually.
          At the bottom of the G-Force fuel pump is a cooling chamber for the canister which houses the HP pump & filter.
          On removal of the cooling line into this chamber water pored out from the supply line. which was good, however on removal of the coolant supply to the low pressure pump no water came out of that feed line.
          Strpping the bottom plate from the cannister I uncovered that severe calcification had blocked the coolant flow through this chamber and therefore there was no cooling of the fuel delivery system whatsoever.
          I believe I have uncovered the cause of the dilemma that has haunted me for months.
          Fuel Vaporization.
          I have ordered a new fuel canister and when it arrives I will fit and report back.
          A basic issue in hindsight that I should have checked earlier, however a lesson learnt, perhaps the hard way.
          It all figures out, well sort of, run under 2000 rpm no problems, over that it takes around 8-15 minutes above 2200 rpm to cut out and lose the fuel pressure in the rail due to fuel vapourisation.
          No coolant flow cooling the fuel delivery system.

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            #35
            Great find ..... congrats !!
            Currently watching from shore while deciding what my next boat will be !

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              #36
              Fingers crossed that you found the root cause.
              Present Boat- 2018 VR5 4.5/200hp Mercruiser
              Last Boat- 1998 Capri 1950CL 3.0 Mercruiser

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                #37
                Well the replacement parts have arrived from the USA.
                Today I had the opportunity to fit the fuel cooling canister onto the G-Force fuel pump assembly with the expectation that what had been diagnosed as a fuel vaporization problem was going to be fixed,
                The cooling system was blocked in the old canister not cooling the fuel.
                Regarding my expectations unfortunately they were crushed, big time.
                Out on the water 2200rpm all good, took it up to 3400rpm and after 30 seconds the motor started shutting down again.
                The 8 odd minute gremlin struck again.
                Wouldn't have minded so much if I hadn't coerced the wife to come down and do the trail with me.
                Is it going to be fixed this time she asks?
                Of course it will be dear.
                Of course she wasn't impressed and there has been talk of a new boat!

                I am totally at my wits end with this one.

                HELP, please.

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