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Thread: Fuel siphoning

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    Fuel siphoning

    I'm trying to siphoning some old fuel out of my car to replace with fresh, so hopefully my first restart attempt will be successful. I am, however, seemingly reaching some obstruction in the filler pipe before reaching the fuel. Is there some trick to siphoning fuel in these cars?

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    Quote Originally Posted by Spandrel View Post
    I'm trying to siphoning some old fuel out of my car to replace with fresh, so hopefully my first restart attempt will be successful. I am, however, seemingly reaching some obstruction in the filler pipe before reaching the fuel. Is there some trick to siphoning fuel in these cars?
    I had the same problem when I started working on the new to me E31. I never did find a way to siphon from filler neck. So pulled seats and removed carriers which I needed to do anyway to replace fuel pumps and hoses.

    The parts diagram doesn't show any obstruction in drawing.
    Last edited by JDP530; 02-19-2018 at 09:44 AM.

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    Why not just fill your tank with new gas and drive around?

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    Quote Originally Posted by radlaw View Post
    Why not just fill your tank with new gas and drive around?
    The gas has been sitting in the tank for almost 4 years with no stabilizer. I don't want to run that through the system (there's a little less than half a tank in there). The fuel lines to the engine were empty, but the fuel was still sitting in the tank.

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    I had to change out the fuel pump and fuel sensor carriers so I was able to clean bottom of tank by hand after pouring a can of seafoam into empty tank and letting it stand for several days. I just wiped out the gunk or tar on bottom of tank that seamfoam dissolved.

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    Quote Originally Posted by JDP530 View Post
    I had to change out the fuel pump and fuel sensor carriers so I was able to clean bottom of tank by hand after pouring a can of seafoam into empty tank and letting it stand for several days. I just wiped out the gunk or tar on bottom of tank that seamfoam dissolved.
    I don't currently have fuel pump work in the plan, and would prefer to leave well enough alone if possible....

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    Go in from the fuel pump?

    So if i wanted (had to) go in from the fuel pump to siphon, what's the removal procedure? What am I likely to break? How hard is it to get replacements quickly? I can't find anything on TimM's site relating at least...
    Attached Images Attached Images

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    honestly, the best way is to pull the pump/float carriers.
    Short of that, if you just need to empty the tank and refill... this is the only way to do it:

    Disconnect ONE of the fuel feed lines from the metal tube on the firewall.
    Attach a longer hose and stuff the end in one of 4 5gallon gas cans available
    Stick a bolt into the open end of the hose dangling now from the fuel rail. (trust me, just do it)
    Jumper 12v to each of the fuel pump relays.
    Turn it off when the tank is drained.

    This works to drain BOTH sides of the tank, something you could never do with a siphon hose from the fuel door pipe anyway... one pump empties the fuel into your cans, the other keeps the tank leveling siphon circuit going so all the gas eventually ends up being picked up by the pumps.

    Do NOT run the pumps dry for any period of time.. .when the hose stops the spit, you quit.

    For 4yr old gas, that's likely enough... for known heavy sediment and sludge, take out the back seats, open the inspection plates, and take the carriers out from both sides of the saddle. This allows you to literally reach inside and mop it up after draining...
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    That's certainly the way I would do it - I did the same when emptying 60 Litres from the leaking tank on my 740i





    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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    This is a great idea! I pulled the seats to take a look last night, got impatient and pulled the pump carrier next to the filler neck (RHS) enough to sneak a siphon tube down into that side of he tank and drained it. Still have ~3-4 gallons in the other side (fuel gauge just above the red zone). Debating if it's worth using this method to get that other side, or just put 10 gallons of ethanol free 93 in there with a bottle of fuel system cleaner and roll the dice...

    The rubber covering on the LHS is whole - the disk flap has not been fully cut. Is there a pump carrier on that side as well in an 840? Or is it just an inspection port (or nothing)?

    Doesn't using the pump to empty pull nastiness into the pump? And if I tried running it now, with one side almost completely empty, do I risk running the pump dry?

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    There's a sender for the fuel gauge on the LHS - and the tank uses a similar fuel circuit to the E38 as detailed below:

    http://www.meeknet.co.uk/E38/Sender/Index.htm

    Using the pump will get the most possible fuel out of BOTH sides of the tank
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    Why not just disconnect the fuel line and run the pump? After all that's what it is made for.
    I deal with long dormant cars fairly frequently and try not to make more work for myself. If removing the sender you'll want to replace the gasket.
    Some E34s have a drain plug on the tank, not sure if that practice carries over to 8 chassis but might be worth a peek.
    Last edited by ross1; 02-21-2018 at 09:26 AM.

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    Quote Originally Posted by ross1 View Post
    Why not just disconnect the fuel line and run the pump? After all that's what it is made for.
    I deal with long dormant cars fairly frequently and try not to make more work for myself. If removing the sender you'll want to replace the gasket.
    Some E34s have a drain plug on the tank, not sure if that practice carries over to 8 chassis but might be worth a peek.
    Disconnect ONE of the fuel lines, either at the pump or on the firewall, it doesn't matter... run a hose from that, jumper both fuel relays and empty the tank. This will drain both sides...
    Last edited by cartoonz; 02-21-2018 at 01:18 PM.
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    Quote Originally Posted by cartoonz View Post
    Disconnect ONE of the fuel lines, either at the pump or on the firewall, it doesn't matter... run a hose from that, jumper both fuel relays and empty the tank. This will drain both sides...
    Cartoonz, have you picked up your 'new' car? Congratulations on purchase!

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    Quote Originally Posted by cartoonz View Post
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    Quote Originally Posted by cartoonz View Post
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    Hmmmm. Got around to trying this today. My E-boz doesn't look like the V8 diagram in the linked PDF on your relay finder, Timm:


    diagram:





    Quote Originally Posted by Timm View Post
    That's certainly the way I would do it - I |did the same when emptying 60 Litres from the leaking tank on my 740i






  20. #20
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    No, mine doesn't either, the picture is from the M60 version. Here's mine



    ...and I expect that the fuel pump relay is the one closest to the camera. But, if I were you I would apply power to Fuse 23 rather than poking the relay....
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    Does it matter which prong gets the positive wire and which the negative? (And thanks for the picture - good to confirm that I put everything back correctly)

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    Timm has it right, fuse 23... power that
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  23. #23
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    You need 0V to the chassis (use the jump point on the suspension tower) and 12V to Fuse 23, you can use either side of the fuse.....
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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