Fuel leak 318is

[A18RPF]

This is an issue that reared its head when my e30 was last on the road, and with a trip to the Nurburgring coming up it needs sorting.
In short the fuel tank only fills halfway before it starts to pour out all over the floor. If you only fill it to half a tank it's fine, but there's obviously a leak. The problem is I don't know if my car (318is) has the smaller or larger tank? As I understand the larger tank is 'bridged' above the prop. The car is up on stands and has a fuel line connecting the two halves of the tank, could this be the culprit?
Just don't want to take the prop off and drop the tank to find there's nothing wrong with it

[daimlerman]

As your car is up on stands,the 'fuel tank test' is easy to do.
Get hold of the inlet stub,just forward of the o/s rear wheel,and give it a good yank.ANY movement indicates that the welded in stub pipe has rust damage.
Repairs are not really advisable,but replacement pattern tanks are available.

[Brianmoooore]

All tanks are 'bridged' above the prop., but only the 55 litre (smaller) tank has a pipe joining the two halves under the prop.

[A18RPF]

So it's still highly likely that the bridging piece above the prop is where the leak is?

[Brianmoooore]

So it's still highly likely that the bridging piece above the prop is where the leak is?

Won't be there. Most common is where the fuel goes nto the tank from the filler, followed by a split O ring for the fuel pump, followed by rust eating through the seam where the top of the tank is welded to the bottom.

[rix313]

I had the O-ring go around the fuel pump and that leaked like crazy. Dealers supply new ones for next to nothing.

[A18RPF]

I've had the pump out and the o ring was fine. It doesn't leak at all unless the tank is over half full

[Brianmoooore]

Most common is where the fuel goes nto the tank from the filler.

[FZB]

BMW will supply a new fuel tank for about £640, it's the fitting and anything else hidden that needs replacing when you remove it that things start to add up.

[Brianmoooore]

There are pattern tanks available, and plenty of good second hand OE ones around, so no need to swell BMW's coffers for this.
I wouldn't dream of replacing the tank without replacing the brake pipes above and behind it.

[FZB]

Very true.

I wouldn't dream of replacing the tank without replacing the brake pipes above and behind it.