Please note this thread has been inactive for 90 days. For the best results, please start a new thread.
Page 1 of 2 1 2 LastLast
Results 1 to 25 of 45
  1. #1
    Cadet
    Join Date
    Apr 2010
    Posts
    22

    Default 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. #2
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,383

    Default 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"

  3. #3
    Cadet
    Join Date
    Apr 2010
    Posts
    22

    Default 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
    =========

    Quote 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?

  4. #4
    Petty Officer 2nd Class
    Join Date
    May 2012
    Location
    LA (lower Alabama)
    Posts
    194

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

    Quote 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!

  5. #5
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    Quote 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

  6. #6
    Honorary Moderator Emeritus Don S's Avatar
    Join Date
    Aug 2004
    Location
    Western WA.
    Posts
    62,323

    Default 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.


    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.

  7. #7
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    Thank you Don, I understand.

  8. #8
    Cadet
    Join Date
    Apr 2010
    Posts
    22

    Default 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
    ========

    Quote 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
    =========

  9. #9

    Default 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.

  10. #10
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    Quote 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

  11. #11
    Cadet
    Join Date
    Dec 2012
    Location
    Long Island, NY
    Posts
    7

    Default 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?

  12. #12
    Cadet
    Join Date
    Apr 2010
    Posts
    22

    Default 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

  13. #13
    Cadet
    Join Date
    Dec 2012
    Location
    Long Island, NY
    Posts
    7

    Default 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.

  14. #14
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,383

    Default 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"

  15. #15

    Default 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?

  16. #16
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    My engine is a 5.7 Gi-C. One of the part numbers I was quoted is the same as you have - 359444 for the whole fuel cell - which includes the low pressure and high pressure pumps and the fuel filter and all attached in one big assembly.

    I have the correct parts, if that was your question.

    In my case, the fuel assembly would be fine if the fuel rail recirculated gas went straight back to the gas tank, as is often done on EFI cars. That would avoid overheating the gas a light loads.

    The fuel cell assembly on my boat is easily able to keep up with demand at full load. The problem arises with the gas overheating at light loads/idle.

  17. #17
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    DaveNix, I think I bought the pump through Amazon, but I cannot find the record now. A similar unit is "DC Converter Voltage Regulator LED Digital Display Power Supply 4.5~24V to 1~20V" at Amazon. Make sure whatever you get can handle the amperage - at least 10 amps continuous. The brand for this unit is Blue Solar.

    Best
    Rod

  18. #18

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

    Rod,

    Thanks for the quick response. I have an earlier MFI system where the LP and HP pumps are separate. The LP pump overheats and fails at idle. I have been chasing this for 3 years and had thought about this type of fix, but wasn't sure it would work. I am glad it does work and can't wait to try it (I'm in the midwest and it is still cold here).

    Thanks Again,
    Dave

  19. #19
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    Dave,

    Please let us know what you find when you get to it. You might need to use a two speed setup, which I had expected to need, but I do not. I just ordered a wireless pressure sensor and remote display/monitor, so I can easily monitor the fuel pressure at the engine in normal use.

    What I am using right now is a fuel pressure gauge attached to and located at the fuel injector rail - so to test load fuel pressure I have to keep the engine cover open.

    Good luck!
    Rod

  20. #20
    Cadet
    Join Date
    Dec 2012
    Location
    Long Island, NY
    Posts
    7

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

    Rodregal. I located a "Blue Solar" Converter Volatge Regulator on Amazon. All the same specs that you referred to except that it stated that the Output current is rated at 2a, 20 w max. Should I look elseware?

  21. #21
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    I did some more digging, and found the source of the voltage regulator that I bought. Suntekstore is the source, and this is the description of what looks like the best fit; "Input AC/ DC 12 - 45V to Output AC / DC 0.7 - 21V 8A Converter Board Step-Down Voltage Regulator Module". They have a few others.

    They are not currently offering the unit that I bought. Shipping was faster than I expected - about a week.

    Cheers
    Rod

  22. #22
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    If you hear the loud buzzing noise, switch off the engine and check which fuel pump is hot. One pump is likely to be cool.

    The pump that is on the outside of the fuel cell and replaceable without dismantling the fuel cell is the high pressure pump. It is possible to buy this pump on it's own without buying the whole fuel cell unit.

    I haven't been able to find the low pressure pump available standalone. It would be great if someone could source it and publish the source here.


    The hot pump is likely to fail soon unless you change something to save it. At least get a spare pump so you can replace it quickly.

    Cheers
    Rod

  23. #23
    Vice Admiral Tail_Gunner's Avatar
    Join Date
    Jan 2006
    Location
    Portland, Or.
    Posts
    5,383

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

    Do you have the ability to measure voltage as the rpm increase's....aka where is the point or rpm level which no longer require's voltage adjustment.
    Stickly a opinion your milage may vary.

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

  24. #24
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    The controller I have installed maintains a constant voltage at the high pressure pump.

    As the pump load increases, it takes more amps from the voltage controller, at constant voltage. In the stock installation, as the pump demands more amps, the supply voltage goes down a little because of resistance in the supply wires.

    I have not measured the voltage setting on my setup.

    What I am monitoring is the fuel pressure at the injector rail. And when I set up the voltage controller I experimented with higher and lower settings. I adjusted it to have a small amount of recirculation through the fuel pressure regulator at idle (which you can feel and hear) , and then carefully load tested it at gradually increasing loads, to make sure that the fuel pressure never dropped below the specified level.

    It helps that the pressure regulator lowers the fuel pressure at maximum load from Volvo. The injectors are programmed to stay open longer at high engine load to counteract the reduced pressure.

    I hope I have addressed your question..

    Best
    Rodregal

  25. #25
    Cadet
    Join Date
    Apr 2010
    Posts
    22

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

    I realized last night that there is an ambiguity in my post yesterday, so this is to further clarify;

    At low engine loads, the injectors use small amounts of gas, and obviously at full load the injectors are open for longer pulses and draw more fuel through the rail. The delivery pressure at the rail does not vary by much from idle up to full power.

    The changes in load/demand on the HP fuel pump are caused by the changing pressure of the gas on the suction side of the hp pump. At full load, the pressure regulator sends almost all the gas straight to the injectors, and the pressure of the small flow of gas through the recirculation line which goes back to the suction side of the hp pump is at a very low pressure. This causes the hp pump to work harder. High amp draw.

    At light load, the amount of gas flowing to the injectors is much reduced, and the pressure regulator recirculates a much higher volume of gas at much higher pressure, back to the suction side of the hp pump. This results in a very low pressure difference from the suction side to the pressure side of the pump. So the pump has a light workload, and draws a low amp current.

    I hope this helps!

    Rodregal

Page 1 of 2 1 2 LastLast

Similar Threads

  1. Please help. Fuel pump solution found but unsure how to diagnose possibilities
    By doeoner in forum Volvo Penta I/O & Inboard Gas Engines & Outdrives
    Replies: 4
    Last Post: September 19th, 2012, 09:23 AM
  2. Vovlo Penta fuel pump problems
    By baf3472 in forum Mercruiser I/O & Inboard Engines & Outdrives
    Replies: 5
    Last Post: August 7th, 2010, 06:08 PM
  3. Volvo Penta fuel pump problems
    By va boater in forum Volvo Penta I/O & Inboard Gas Engines & Outdrives
    Replies: 10
    Last Post: July 13th, 2009, 08:00 PM
  4. Volvo Penta fuel pump problems
    By va boater in forum Boat Topics and Questions (not engine topics)
    Replies: 1
    Last Post: May 16th, 2009, 03:48 PM
  5. Fuel pump solution and a newby
    By Macwrench in forum Johnson & Evinrude Outboards
    Replies: 2
    Last Post: July 27th, 2008, 10:19 AM

Tags for this Thread

  1. iboats Forum Directory - Over 100,000 forum posts organized by topic