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My solution for fuel pump problems on 5.7 Gi and Gxi Penta

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  • My solution for fuel pump problems on 5.7 Gi and Gxi Penta

    I have learned a lot from reading through all the posts here and elsewhere about the fuel pump/fuel cell problems on these engines - because my 2003 Regal has a 5.7 Gi engine, and I have had many fuel system problems, which at first I did not recognize.

    I have found the black paint inside my "fuel cell". My LP fuel pump and my HP fuel pumps have failed. The Pressure Regulator failed from being clogged with the black paint.

    I am a qualified Electrical and Mechanical Engineer. And I was unwilling to simply pay Volvo the money and wait for the next time the fuel system would let me down.

    I found that with all the components of my fuel system replaced and running properly, the temperature of my HP pump was too high at light engine loads. The pressure regulator was doing it's job, as was the water cooling. But having both pumps at full power (which is inherent to this Volvo design) simply generated too much heat in the HP system, recirculating gas as it does, in large volumes, at idle and light load.

    I found that the HP pump was tending to make the loud noise that it does when it is cavitating on the suction end. The cavitation was caused by the gas getting so hot that it was vaporizing on the suction side of the pump. This cavitation will pretty quickly cause the HP pump to fail.

    Basically the "fuel cell" water cooling is inadequate for the amount of heat generated at idle and light load. I decided to change my setup to solve this basic problem. I bought a voltage regulator and installed it on the HP pump. This DC 15 volt device allows me to turn a potentiometer and adjust the speed of the HP pump.

    I expected that I would create a set point for idle and light load, set the speed control at that point, and then my intent was to install a micro switch that would be operated by throttle position, and which would apply full power to the HP pump at high loads.

    Then I tested the voltage controller on the system, and chose a good set point to reduce the amount of gas recirculation taking place at idle and light load. Doing this stopped the temperature gain in the HP gas system very effectively. The HP pump was running cool for the first time.

    I then took the boat out and tested the fuel system at various loads and speed settings on the HP pump. What I found was very surprising; The HP pump speed setting that worked well at idle also worked well at full power.

    This says to me that the set point I am using is a good balance between the LP pump and the HP pump. That they work better as a pair with the setting I am using. I am monitoring HP fuel pressure at all times, and I may decide over time to install the microswitch. But at sea level, on my boat, with ambient air temperature of 65 deg F, and humidity of about 40%, my fuel system is working better than ever, the pumps are not overheating, and the HP gas is staying nice and cool.

    Obviously I will monitor the situation and the setting carefully. It may well be the case that I will find some operating conditions where I will want to use the pressure switch to set the HP pump to full power.

    Your mileage may vary. But I am happy with my system, and I am making this post so that others who are struggling with this poorly designed fuel system are able to use what I have learned and experienced to reduce their downtime and wasted money.

    I hope this helps

    Rod


  • #2
    Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

    Nice post and a question if i may, lowering the voltage to the pumps is that harmful and your fuel pressure does it stay steady...Is this a tbi engine or mpi?
    Stickly a opinion your milage may vary.

    Speed is how fast you hit the wall
    Torque is how far you move the wall"

    Comment



    • #3
      Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

      Thank you. Lowering the voltage to the High Pressure pump is not harmful to the pump. I have a pressure guage hooked up to the Schrader fitting on the high pressure fuel rail, so I can monitor it. I have set the HP pump speed so that the fuel pressure is steady at all loads on my boat (all loads in the recent winter weather in San Diego). When I deliberately adjust the HP pump speed down to too low a speed, then the first sign is that the fuel pressure fluctuates. When I lower the pump speed further, the fuel pressure drops. It is easy to see and easy to set. I bought a fuel pressure guage from Amazon that cost $28 to monitor the setup.

      My engine has electronic fuel injection, at each cylinder.

      By how the two pumps are working together so well now, it seems to me that I have matched the speed of the LP and the HP pumps with each other so that they work well in unison. Different engines will I am sure need the installation of a micro switch, so that the HP pump can be switched to full speed at high loads.

      Hope this helps!
      Rod
      =========

      Originally posted by Tail_Gunner View Post
      Nice post and a question if i may, lowering the voltage to the pumps is that harmful and your fuel pressure does it stay steady...Is this a tbi engine or mpi?

      Comment



      • #4
        Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

        Originally posted by rodregal View Post
        ... But I am happy with my system, and I am making this post so that others who are struggling with this poorly designed fuel system are able to use what I have learned and experienced to reduce their downtime and wasted money. ...
        Assemble a kit for sale and I am in for one!

        Comment



        • #5
          Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

          Originally posted by doyall View Post
          Assemble a kit for sale and I am in for one!
          Thanks Doyal

          I will think on how practical it is to make a kit.

          Rod

          Comment



          • #6
            Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

            Just an FYI, you don't want to get into trying to sell things on the forums, it's not allowed.

            I can just imagine the problems that could come up when a DIYer with no clue what he is doing, tries to install something like that, just because he thinks it's a cure-all and will save him some money.
            It doesn't make any difference to them if they have a Mercruiser, or a Volvo, carbed or EFI, they will try it. Seen it too many times in these forums.
            Don S.

            sigpic

            Please, no PM's (Private Messages) regarding boat/engine problems.
            That is what the forums are for.
            Only forum/moderator issues will be answered in PM's.

            Comment



            • #7
              Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

              Thank you Don, I understand.

              Comment



              • #8
                Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                To put this in perspective; with the stock setup on my boat, the high pressure pump temperature built up to about 100 Deg F at idle. At idle the maximum amount of fuel is flowing through the pressure relief valve and through the bypass circuit and back into the high pressure pump, so the same fuel gets recirculated over and over and heated up more on each time though. That is what the water cooling of the "Fuel cell" is for. On my 5.7 Gi 2003 engine, (which uses the exact same fuel pumps/fuel cell parts as the Gxi), the water cooling is no where near capable of keeping the gas and HP pump temperatures down at idela and light load.

                In my system, I can adjust the speed of the high pressure pump slower to reduce how many circuits the gas makes through the bypass circuit. My high pressure pump runs at about the same temperature as the gas in the tank. Both the low pressure and the high pressure pumps are running nice and cool. So they will likely last a long time.

                Hope this helps!
                Rod
                ========

                Originally posted by rodregal View Post
                Thank you. Lowering the voltage to the High Pressure pump is not harmful to the pump. I have a pressure guage hooked up to the Schrader fitting on the high pressure fuel rail, so I can monitor it. I have set the HP pump speed so that the fuel pressure is steady at all loads on my boat (all loads in the recent winter weather in San Diego). When I deliberately adjust the HP pump speed down to too low a speed, then the first sign is that the fuel pressure fluctuates. When I lower the pump speed further, the fuel pressure drops. It is easy to see and easy to set. I bought a fuel pressure guage from Amazon that cost $28 to monitor the setup.

                My engine has electronic fuel injection, at each cylinder.

                By how the two pumps are working together so well now, it seems to me that I have matched the speed of the LP and the HP pumps with each other so that they work well in unison. Different engines will I am sure need the installation of a micro switch, so that the HP pump can be switched to full speed at high loads.

                Hope this helps!
                Rod
                =========

                Comment



                • #9
                  Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                  I understand what you are saying but how is this going to help the black paint problem? I thought the paint problem and the pump problem were tied together because of blockage.

                  Comment



                  • #10
                    Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                    Originally posted by davidlees View Post
                    I understand what you are saying but how is this going to help the black paint problem? I thought the paint problem and the pump problem were tied together because of blockage.
                    Sorry I did not explain. You are right that the black paint spreads through the fuel system and causes problems.

                    In my case, I disassembled the fuel cell and removed all the loose black paint, and all the other black paint that I thought was at risk of falling off, which is a partial solution, before I reassembled it. I also found the black paint in the HP pump intake mesh, in the pressure regulator (which failed from this), and in lots of other places in the fuel cell itself.

                    I have no way of knowing what portion of the fuel pump failures are from the paint versus from the pumps running too hard and overheating. I do know that on my boat, after I assembled the fuel cell with new pumps and no loose black paint, I had a definite problem with the high pressure pump. At startup from cold the pump was fine. But the longer at idle, the hotter the HP pump got till it was too hot to touch. It would have failed very quickly if I did not solve the problem.

                    These fuel cells have two design defects - the one I posted about and the black paint. Ideally we solve both and get to use our boats more!

                    I also think that having a dash mounted remote fuel pressure gauge would help a lot. If I had one I would have saved a lot of time when I first started having fuel problems. My mechanic misdiagnosed the issue and had me waste money on other things.

                    Best
                    Rod

                    Comment



                    • #11
                      Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                      Very interesting post. I'm sure I can speak for others and thank you. Is your motor fresh or raw water cooled?
                      What pressure at the rail did you find to be best for your situation?

                      Comment



                      • #12
                        Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                        Thank you.
                        My boat is raw water cooled.

                        I have not changed the fuel pressure at the rail.

                        The stock setup has the pumps cranking at full load/speed and as a result the fuel bypasses the injectors and is recirculated through the high pressure pump at high speed, when the engine is lightly loaded. This overheats the gas.

                        What I have done is to reduce the speed of the high pressure pump so the amount of recirculation is reduced. But my pressure regulator is always sending gas through recirculation, so the pressure is still controlled by the pressure regulator.


                        My pressure regulator holds 55psi at idle and 45 psi at full throttle.

                        Cheers
                        Rod

                        Comment



                        • #13
                          Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                          Thank you for explaining more in depth. The reason I am so concerned is that my boat is in for winter service, by a certified Volvo shop. However they are going to replace the fuel pump assembly for the third time since April 2007 when I recieved ownership of the boat new. My 2&4 warranty is up this April, so here on in I'm on my own. I will run this whole thing by the mechanic and let all know what he thinks. Personally I think you nailed it.

                          Comment



                          • #14
                            Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                            I checked my 4.3 throttle body injection system for this idle condition, no over heating was present. So I did a little parts search and found something a bit odd. Volvo use's the same high pressure pump for both Throttle body and Mpi motors. With that in mind TBI uses 30lbs of pressure on the high side and MPI uses 50lbs on the high side. To the original poster could you post the model number of your engine for exact clarification. If I am right it is only MPI that suffer's from this...Just curious and I may be off on this.

                            Fuel System 5.7GiI-B, 5.7GXiI-C - 7744230 - Volvo Penta
                            3861355
                            3594444
                            21397771
                            21545138
                            Replaced by
                            21608511

                            Fuel System 5.0GIPEFS, 5.7GSIPEFS - 7797478 - Volvo Penta

                            3860210
                            3861355
                            3594444
                            21397771
                            21545138
                            Replaced by
                            21608511

                            The upper link is MPI and the lower link is TBI it appears the same pump is running a 30lbs and 45 lbs. There maybe a simple solution here.
                            Stickly a opinion your milage may vary.

                            Speed is how fast you hit the wall
                            Torque is how far you move the wall"

                            Comment



                            • #15
                              Sign up today
                              Re: My solution for fuel pump problems on 5.7 Gi and Gxi Penta

                              Where did you buy the voltage regulator/potentiometer. Do you have brand/model number?

                              Comment


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