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Thread: Fuel Transfer Problem...Need Help ASAP

  1. #1
    Join Date
    Dec 2009
    Location
    manteca,ca
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    2
    My Cars
    98' 528I (e39)

    Fuel Transfer Problem...Need Help ASAP

    I have a 98' 528i (E39) and I am having problems with fuel. The car starts and runs great but, fuel does not transfer from the sender side of the fuel tank to the fuel pump side of the fuel tank. It has a saddlebag style tank, and I understand there is a pipe linking them together. I took the pump out today and i noticed that where the pump clips into (the plastic housing) there is a crack on the bottom of it. Now, it does not intervene with the pump or the line coming from the sender side, and i can't see if it damaged the transfer pipe. So first question is what makes the fuel transfer? Does the pump come into play? or is it by pressure from the sender side? Can anyone help, I would appreciate it.

  2. #2
    Join Date
    Jan 2009
    Location
    Amsterdam, Netherlands
    Posts
    438
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    1997 E39 523i 5spd
    I suppose it's a pump, because it's almost impossible otherwise. I think it's number 7 on this pic, not sure though. It's called "Left sucking jet pump"


  3. #3
    Join Date
    Jun 2007
    Location
    Fort Myers
    Posts
    668
    My Cars
    528i / M35 /C240
    If you will need fuel pump or sensor let me know !

  4. #4
    Join Date
    Oct 2004
    Location
    Falls Church, VA
    Posts
    1,039
    My Cars
    '90 325iX, '00 528iT spo
    The left sucking jet pump is a suction / siphon pump. When you clip the fuel pump into the plastic base in the tank .. it draws fuel from the driver's side saddle through the left sucking jet pump.

    I redid my fuel system (senders, pump, sucking jet pump, 3/2 running loss valve and FPR) and once you have both covers off and senders / pump removed you can see with a flashlight how things are attached.

    I do not know (didn't investigate) how the plastic base lock unit is attached to the bottom of the tank but .. if that is what is broken, and not securing your fuel pump in the proper location .... it is what will prevent the proper suction / siphon draw from the driver saddle through the left sucking jet (siphon).

    Make sure battery is disconnected and you are working in a well ventilated area. Don't smoke when working on this.
    Jason

    '90 325iX 5M, '00 528iT 5M Sport (mfg. 5/1999)
    BMW CCA member #130075
    JScott Racing

  5. #5
    Join Date
    Dec 2009
    Location
    manteca,ca
    Posts
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    My Cars
    98' 528I (e39)
    Thank you to the responses. The suction jet is what i was leaning towards but wasn't sure how it all worked. I have already replaced the pump and sender so ruling out those two. Something i probably should have mentioned before was that the vehicle was in a accident, in which the oil pan was damaged the radiator condensers and it went all the way back to the fuel tank. I bought the vehicle for $200 and figured i could fix it all up for a good price, didn't think about the headaches. Anyway, there is a scrape right under the fuel pump on the outside of the tank, this is where i believe the crack in the fuel pump base came from. There is no fuel leakage but i am really starting to think it may be damaged underneath where the suction jet and the fuel pump meet, so there for there is not enough pressure between the two to draw gas. Any of this make sense enough to possibly be the problem. Thank you again. Today i will be removing the sender unit again to double check things.
    Last edited by mad5150; 12-10-2009 at 05:06 PM.

  6. #6
    Join Date
    Nov 2006
    Location
    Virginia
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    176
    My Cars
    540i6/323is/E21 323
    I would try replacing your fuel filter first the suction jet runs off of return fuel pressure and when fuel filters get clogged pretty bad they can effect the fuel transfer. So try that first if you don't have a new one in there allready it's cheap and known to cause problems with that. It might mot be your problem but its a good start.

    They need to be replaced on a regular basis anyway around 100k. I have seen them clogged completely at around 30k from people getting gas at poor gas stations. Brown sediment can poor out when you take it off.

  7. #7
    Join Date
    Jun 2007
    Location
    Grapevine, TX
    Posts
    144
    My Cars
    '97 M3, '01 530i, '02 M5
    I just replaced item number 7 (left sucking jet pump) in the diagram above in the wife's 2001 530i a few weeks ago. The classic sympton is that you run out of gas while your gas gauge still shows you to have somewhere between 1/8th and 1/4 tank of gas left! This in turn a.) leaves your wife stranded on the side of the highway, and b.) leaves BOTH of you stranded and walking back home after leaving church one very hot Sunday afternoon. Upon removing the back seat, and pulling the two covers to the tank you can see the driver's side half of the tank has gas while the passenger side (with the fuel pump) is empty (or thereabouts). I pulled the old siphon jet out the tank, inspected it, blew it out with compressed air, etc. and reinstalled it. It actually looked fine, no cracks, etc. but I'm guessing (and this is just a guess) the o-rings or some internal part were simply not holding a vacuum as the cleaned up unit did not make a difference. I picked up a new one from the dealer and sure enough it worked like a champ. I put it in, and popped the covers back on and let the car run for a few minutes. Before I did all this I checked the OHM resistance on the fuel senders on each side to see what each one was reading. Afterwards, I did the same thing and they essentially reversed (i.e. fuel was being siphoned to other side). Just to confirm, after a few minutes I pulled the covers back off and sure enough the gas had siphoned to the passenger side - that was a sweet feeling. A few important tips:

    1. The siphon jet comes with two new gas tank cover seals - you do not need to buy them separately.

    2. Make sure you tighten the locking rings nice and tight - you don't want a leak (ask me how I know).

    3. When I bought mine, the dealer confirmed this is a DISCONTINUED part and there are only supposedly only a handful left in the country. If you've been putting this repair off (i.e. and just making sure you always have a 1/4 tank of gas showing on the gauge), you might want to rethink that.

    Good luck!

  8. #8
    Join Date
    Feb 2010
    Location
    Maryland
    Posts
    57
    My Cars
    1997 528i, 2009 330i
    Sorry to bring this thread back up from the dead, but I've been experiencing some fuel transfer issues I am having trouble diagnosing. So far i've replaced the fuel filter, fuel pump, both fuel sending units and the suction jet. Problems I was experiencing before were fuel gauge only reading empty. But all else was fine. I replaced the sending units which solved the issue. I then started running out of gas when the driver side tank was still mostly full. I then replaced the suction jet and the gas pump while I was at it. Ever sense then, I am still running out of gas on the passenger side with none of the gas from the driver side spilling over. I've taken it apart a few times to make sure all of the parts are tight and in order, everything seems to be fine. Does the suction jet on the passenger side connect to the fuel pump in anyway? Mine is clipped into the housing which the fuel pump connects to but both hose ends are exposed and just "dump" out into the tank it appears. There is obviously no mechanical or electric parts associated with this suction jet, so I am sort of confused as to how to "pumps" fuel from one side to the other while seemings having no electric "pump" what so ever. Any suggestions to how this suction jet actually works or how is is supposed to be installed would be great help. Should I have filled, or ran fuel through the pump itself to get a siphon going? Totally confused, seems this should be an extremely simple task, but so far I've had very annoying luck with this.

  9. #9
    Join Date
    Apr 2008
    Location
    Australia
    Posts
    513
    My Cars
    E39 99 528iT
    The sucking jet pump is a simple venturi arrangement. Fuel is pumped to the engine continuously and what is not consumed is returned to the LH side of the tank. The returning fuel is used to create the venturi action in the jet pump and this sucks/transfers fuel in the LH side to the RH side along with the returning fuel. Its purely a passive device with no connection to the RH side fuel pump.

    RonR
    Last edited by Aussie528iT; 10-06-2011 at 07:46 PM.

  10. #10
    Join Date
    Feb 2010
    Location
    Maryland
    Posts
    57
    My Cars
    1997 528i, 2009 330i
    Ron, that was my assumption, but I honestly had no confirmed idea. Thank you so much for clarifying, your response is greatly appreciated.

    Looking into this further, I think I've located the issue. I had confirmed suction jet problems. After replacing, and the problem seemingly being the same, I assumed it was still a suction jet issue.

    Problem went like this. After replacing, fuel pump, suction jet, both level sensors, and fuel filter. My gas gauge which was previously only reading "empty" went back to full. The fuel was pumping regularly, and the car started up just fine. All seemed right with the world. I typically can get around 350-400 miles on a full tank of gas before having to refill (when the gauge only read empty). This past time, right before posting my last issue, my gauge read half of a tank, and I was at around 280 miles. For fear of being stranded, when the car started to putter (indicating it was almost out of gas) I pulled into a gas station which was luckily right next to me at the traffic light. I filled up completely full, and the pump read 16.5 gallons filled. That only leaves me 2 gallons of gas, about 1/8 a tank and a lot less than half of a tank. After reviewing my average driving condition since the last fill up, I've been mostly on city, stop and go traffic. I averaged it to about 18 MPG which is typical EPA for a 528i on city driving (especially with my 207,000 miles). I believe the only real issue is that my driver side floater appears to be "stuck". Once the level of fuel goes down a bit, I plan on taking the driver side tank back part and checking to make sure nothing is blocking the floater from reaching the bottom. I can post back here with the final results. I guess it should pay to not try and link past problems with new ones even if they DO seem to be the same issue. I have a bad tendency to do that sometimes.

  11. #11
    Join Date
    Oct 2004
    Location
    Falls Church, VA
    Posts
    1,039
    My Cars
    '90 325iX, '00 528iT spo
    jma:

    You can check the resistance of the floater "arm" as you move it through it's range with a DVM before replacing. Remove sending unit / floater / arm assembly from tank and connect DVM. Manually move arm through range and follow resistance measurements. Values are in the Bentley manual.

    When I went through diagnosing an intermittent no-start condition ... I "refurbished" my fuel system with a new pump, two sending units, sucking-jet pump, fuel filter and a 3/2 running loss valve (under driver side, incorporates fuel pressure regulator) which is only on '99/'00 528s and one or two years of the 540s.

    Peace of mind in having new components (160k miles at the time) though, my particular problem was an internally corroded + wire to the fuel pump, just under the passenger side sending unit cover .. only discovered when jumpering fuel pump, cover off, wriggle wires. Was a PITA to diagnose.

    Good luck.
    Jason

    '90 325iX 5M, '00 528iT 5M Sport (mfg. 5/1999)
    BMW CCA member #130075
    JScott Racing

  12. #12
    Join Date
    Feb 2010
    Location
    Maryland
    Posts
    57
    My Cars
    1997 528i, 2009 330i
    jase,

    Thanks for the additional suggestions. I wasn't planning on replacing the sending unit just yet, but merely checking it. Once fuel goes down I will check it out and report back here. I have a second left side sending unit I got bundled with some other fuel pieces when doing this refurb, so if all fails, I will install that one and see, but the sending unit I have in there now is brand new, so I doubt it's faulty.

    Appreciative as always.

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