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X5 E70 (2007 - 2013)
E70 BMW X5 produced between 2007 and 2013. Discuss the E70 X5 with other BMW owners here.

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  #1  
Old 08-09-2014, 09:39 AM
Ifndoubtflatout Ifndoubtflatout is offline
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Mein Auto: X5 35D E70
Question Fuel cut out at just under 1/4 tank

I have a 2009 X5 35D E70 which on several occasions just shuts off and screams to a halt when the fuel gauge is at one notch below 1/4 of a tank. The car is not out of fuel as it only takes about half a fill to fill it up. However, if I add one gallon of fuel, it'll start back up and run.

So I took out the back seat and had a look and I see that I have one submerged pump on the drivers side and a syphon system on the passenger side of the saddle tank. It seems to me that I am emptying only one side of the tank, but having now looked at the plumbing I need someone to explain how the fuel ever gets used from the passenger side of the vehicle as it aint obvious how that fuel jumps over to the other side of the tank. Yes, the hose is there, but not sure I understand how the syphon system works ( or doesn't as the case seems to be)

Thanks for any comments from someone who has suffered this pretty exciting type of fault as it'll waken you up on a highway/motorway as these cars do stop fast when they run out of fuel and shut off.
cheers
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  #2  
Old 08-09-2014, 03:04 PM
ninja_zx11 ninja_zx11 is offline
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This will help you to understand the plumbing inside the tank.

Did you even find the surge chamber dry?It could be the faulty left delivery unit?just guessing.
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Last edited by ninja_zx11; 08-09-2014 at 04:25 PM.
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  #3  
Old 08-09-2014, 11:50 PM
ard ard is online now
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Mein Auto: '12 X5 35d/E39M5/996TTX50
Common issue with E39s. There is a siphon jet pump on one side that just continuously dumps fuel to the other side. Then THAT side is where the main pump is.

If the siphon pump fails, once the fuel level drops below the saddle the one side stays full- the main side runs dry and you run out of fuel still showing 1/4 tank
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Old 08-10-2014, 02:48 AM
Ifndoubtflatout Ifndoubtflatout is offline
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Mein Auto: X5 35D E70
Thanks ninja .... Thanks so much for the diagram..... extremely helpful. I have no idea how the Suction Jet Pump operates as it has no power to it and so I assume its operated somehow from the fuel return line which is somehow meant to lift the fuel from the left to right side of the tank. Anyway, from what I can see, the only possible faulty item can be the Suction Jet Pump on the left (non fuel pump) side of the tank.. I see between the E70 and E90 they have added a check valve, but not sure that this is related.

Last edited by Ifndoubtflatout; 08-10-2014 at 02:54 AM.
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  #5  
Old 08-10-2014, 02:52 AM
Ifndoubtflatout Ifndoubtflatout is offline
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Hi ard.... I suspect you are 100% correct. Have you any idea how this Suction Pump is meant to operate as its not a 'real' pump is some type of plastic tower with no 'real' electrical pump. Seems a touch flaky to me for BMW, but maybe it clever and works 'most of the time'. Thanks again for your help.
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Old 08-10-2014, 07:41 AM
ninja_zx11 ninja_zx11 is offline
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Quote:
Originally Posted by Ifndoubtflatout View Post
Have you any idea how this Suction Pump is meant to operate as its not a 'real' pump is some type of plastic tower with no 'real' electrical pump. .
Suction jet pump works on the venturi effect.As the fuel from return line travels back to the right hand side of tank where the main fuel pump is,it goes through left delivery unit which contains a venturi suction pump .So the returning fuel draws fuel from the left side of tank to right side of tank(venturi principal).

I suspect there is a problem with your left delivery unit which contains venturi suction pump.Try to remove the left unit and check it.It could be just a blocked venturi ,bad air inlet valve ,loose or cracked hose because there is nothing electrical in the left delivery unit except the fuel level sensor.

here is the link to left delivery unit.http://parts.bmwofsouthatlanta.com/s...driveLine=6471

There is also a chance of blocked or bad suction pump which is in the right delivery unit.It pulls returning fuel to the surge chamber.So better to take out both delivery units and inspect them.It will be interesting to know!!

Please note that i am not an expert and just trying to help you with help of diagrams and parts list.
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Old 08-10-2014, 08:14 AM
ninja_zx11 ninja_zx11 is offline
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I just found a test procedure documented in TIS.
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  #8  
Old 08-10-2014, 10:11 AM
ard ard is online now
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[QUOTE=ninja_zx11;8517447].It could be just a blocked venturi ,bad air inlet valve ,loose or cracked hose because there is nothing electrical in the left delivery unit except the fuel level sensor./QUOTE]

^ Spot on. An issue Ive seen in other cars is a cracked hose in the tank- you are dumping gas back into the tank, but the car is starving for fuel but all external indications are 'pump is working'.

In this case a crack or loose hose will dump return fuel into the one side, which will then spill over...so no symptoms until the right side runs dry.

Quote:
Originally Posted by ninja_zx11 View Post
Please note that i am not an expert and just trying to help you with help of diagrams and parts list.
Well, thats all one generally needs!


anyway OP, report back once you get it fixed...
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