How to tight the in-tank fuel pump up to the assembly?

Discussion in 'General Motoring' started by martinxue, Feb 26, 2006.

  1. martinxue

    martinxue Guest

    Hi,

    In order to investigate a fuel system problem (the car stopped after
    using 1/3 of the fuel in the tank), and after for the first time taking
    out the in-tank fuel pump for my 1988 240GL Volvo on this Sunday, I
    found out that the in-tank fuel pump was only connected to the assembly
    line by one cobble line (to one of the pump's electric connector). The
    fuel hose connecting between pump and the steel fuel line was
    completely broken and disconnected, and the pump can move up and down
    inside a plastic gasket without any constrains (luckly it did not slip
    into the tank)!

    After I removed the gasket from the assembly and took out the fuel
    pump, the cobber line connect to the pump was also broken. I think I
    can later on connect the cobber lines to the 2 electric connectors in
    the pump. And I also tested the pump with a 12-Volt electricity
    withouth problem, the pump works fine.

    I am going to buy a new fuel hose, but the question worries me now is
    that: how to connect the pump to the assembly? If I only put it into
    the gasket it can still move up and down, and it will be only
    physically connected by the fuel hose and 2 electric lines to the
    assembly. Is that correct? Or I missed something important that tight
    the pump up to the assembly?

    I search the Hayne's manual and Internet, but still could not find a
    explict description on how to tight the pump with the assembly?

    Can anyone shed any lights on this issue? I'll be greatly appreciated.

    Thanks very much.

    Regards

    Martin
     
    martinxue, Feb 26, 2006
    #1
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  2. The pump assembly I'm used to working with on my 760 is different, I know,
    but on the 240s I seem to recall people saying it was held down by a
    castellated nut - a large nut with bumps like the top of a Spanish castle.
    Mostly I recall complaints about how hard it is to get loose. Are there
    threads around the pump area that would suggest that nut is missing?

    Mike
     
    Michael Pardee, Feb 26, 2006
    #2
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  3. I'm sorry - I didn't read the post closely enough. You are asking about the
    connection *inside* the tank.

    That thin bellows usually tears, causing the symptoms you have. I did what
    most people do, replacing the bellows (which is not available separately
    anyway) with a short piece of fuel hose and clamps at each end of the hose.
    Keep the hose short, because if it is too long it will jam against the
    bottom of the tank and block flow. Of course, a short hose will keep the
    pickup off the bottom of the tank and not allow the very last gallons of
    fuel to be used.

    Mike
     
    Michael Pardee, Feb 26, 2006
    #3
  4. martinxue

    martinxue Guest

    Hi Mike,

    Thanks very much for your reply.

    Just want to clarify the comments, do you mean that there is only the
    fuel hose that connects and tight up the in-tank fuel pump to the
    assembly (besides the 2 cobber electric lines to the pump's 2 electric
    connectors)?

    I am wondering if it is like that, the pump can move up and downs
    freely inside the gasket, the hoses will always have the "downside"
    pressure because of the weight of the fuel pump and it will "tear" off
    the hoses sooner or later?

    Thanks.

    Regards

    Martin
     
    martinxue, Feb 26, 2006
    #4
  5. martinxue

    James Sweet Guest


    Yep, that's how it is. The idea is that the pump floats in the bracket,
    so the pickup sock can rest right down on the bottom of the fuel tank
    yet not be smashed against the bottom of the tank. Fuel hose is pretty
    strong, I think you'd break the plastic fitting on the pump before
    tearing the hose.
     
    James Sweet, Feb 26, 2006
    #5
  6. martinxue

    martinxue Guest

    Hi,

    Thanks for the ideas and suggestions. Then in that case I suspect that
    the fuel hose in my tank was a bad one since it was completed broken
    and torn off. The fuel pumps (both internal and external) were replaced
    by a mechanics several months ago.

    Does anyone know what the hose should be like?

    Thanks.

    Regards

    Martin
     
    martinxue, Feb 26, 2006
    #6
  7. The original was a thin, folded rubber piece that allowed the pump to move
    up and down. That is really too fragile and isn't available separately
    anyway. I used standard fuel hose (is that 6mm?) and a pair of worm clamps.
    If you take the pump to the auto parts store and say "I want a short piece
    of fuel hose to fit this" you will get something that works. I think the
    piece I used was something like 5cm long but I had to buy a foot of it.

    Mike
     
    Michael Pardee, Feb 26, 2006
    #7
  8. martinxue

    martinxue Guest

    Hi,

    Maybe this is a naive question, but if the goal is to pump the fuel out
    of tank, why does it need to let the pump to float on the surface of
    the gasoline and not just tight the in-tank fuel pump to the bottom of
    the tank?

    Unless it is required that the in-tank fuel pump can not be submerged
    into the gasoline?

    Thanks

    Regards

    Martin
     
    martinxue, Feb 26, 2006
    #8
  9. martinxue

    James Sweet Guest


    It rots out with age, rubber just breaks down like that.

    Just get a piece of standard rubber fuel line of the right diameter,
    IIRC it's 5/8", but take the prepump with you to the store.
     
    James Sweet, Feb 26, 2006
    #9
  10. martinxue

    James Sweet Guest


    It doesn't float on the surface, it floats on the bottom of the tank. If
    the pump mount and tank dimensions were precision made then the bracket
    could be rigid, but things vary so the idea is to give the pump some
    slack so the pickup can rest on the bottom of the tank without smashing
    against it and clogging.
     
    James Sweet, Feb 26, 2006
    #10
  11. martinxue

    martinxue Guest

    Hi,

    I still do not fully understand how it works. If the in-tank fuel pump
    was connected to the fuel feed line (mounted on the assembly) by the
    fixed-length fuel hose, then how would it move up and down freely,
    unless the hose can be "dynamically" shortened or extended?

    Or another "explanable" way is that the pump should be tighted up to
    the assembly so that its pickup socket can be able to reach the bottom
    of the tank, then it pumps gasoline through the hose to the fuel feed
    line without moving up and down when the level of the gasoline in the
    tank changes.

    But it was not like in my Volvo, as there is a gasket which was mounted
    to the assembly and the pump was slided into the gasket and can be
    moved up and down.

    Possiblly there are some parts missing, as the fuel pump was replaced
    serveral months ago by a mechnics and I remembered after I ordered the
    fuel pump for him, he said that there was something parts was not
    fitted for that pump but he somehow "managed" to get it working.

    Am I missing something?

    Thanks.

    Regards

    Martin
     
    martinxue, Feb 27, 2006
    #11
  12. No - it sounds like you have it all there. After the repair the pump will no
    longer be free to extend to the bottom of the tank, so the last gallon or so
    of gasoline won't be picked up. Before the pickup filter sock was able to
    rest on the bottom of the tank, but now it won't. But as long as you don't
    try to get the last mile or km out of the tank you'll do just fine.

    Mike
     
    Michael Pardee, Feb 27, 2006
    #12
  13. martinxue

    martinxue Guest

    Thanks.

    I will buy the fuel hose to connect the pump to the fuel feed line.
    The length of the hose will be measured so that the pickup socket would
    be able to reach the bottom of the tank. Since the hose's length is
    fixed I will secure the pump to the assembly (sending unit) and won't
    allow it to move up and down.

    Are there any problem with this approach?

    Thanks

    Martin
     
    martinxue, Feb 28, 2006
    #13
  14. martinxue

    User Guest

    No. If you're being that particular size the hose length with the tank
    about a quarter full, that way as it changes size during filling and
    heating you won't be far wrong from ideal a high percentage of the time.

    Bob
     
    User, Mar 1, 2006
    #14
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