That's a great depiction of the tank and how it works. 10,000% better than BMWs own since they copied the page from the sedan which does not have the pit and they drew the left and right lobes the same size and symmetrical.

A minor difference is that the right gauge will actually read about 1.4L of the 5L pit so the unlisted "sacred" amount meant to keep the pump always submerged is about 3.6L

I would have flipped the drawing to have right on the right side but see you drew to match the photos taken from the front.

If you catch yourself as you are about to run out of gas from a failed siphon jet you can make a hard left turn (with any luck a U-turn to a gas station you just passed) I bumped into several threads where people mentioned success with this trick in sedans while doing my fuel system research.

This trick or the one to Jack the left side will likely not work on the X5 however, because as the o-ring seal fails, it still will siphon some gas it just relies on the depth of the fuel to help that's why some people run out of gas at 30 miles to empty some people run out at 75 like when happened to me. The wear level of the electric pump comes into play as well: stronger electric pump will push more fuel volume and pressure back to the siphon and will work longer with the leak.

The other problem is you don't get to use all the emergency gas you put in: anything over 5L will spill info the left lobe of the tank and the pump will suck out more than you consume and send it over to the left side so you can't drive very far with the siphon jet failed and a boost of 2gal from a plastic can of gas. (eg though 2 gal should get you 30-40 miles it might only get you 5-10. )

One last thing: test six works when the car is on not running so if you do stall while driving you can perform test six to confirm a siphon jet vs electric pump failure. If both sides have plenty of gas eg 402153 expect fuel pump failure. If you see 254000 it's a sure sign of siphon jet failure. If indicating siphon jet failure you don't need a tow just 5L of gas to drive to a near station where you can add more than 30L to flood to the right lobe. Then do the fix above and it'll be good until the elec pump fails.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)