Sadly I just rummaged for parts in my basement and never measured the o-ring. If you look at my master thread on fuel system diagnosis I may have taken a pic with my calipers to show the size.

The size is certainly metric and a standard size you could buy at a hardware store. I had some flashlight o-rings like 18-19-20mm in my basement I thought it was one of those but the other seal is about 27 it could be in that range as well. If nobody beats me to it I'll get a measurement the next time I take apart one of these.

I already did both mine and wife's but I will do the siphon refurbish on any BMW before about 4000 hours


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So to confirm, the Teflon Tape was the way to go and you haven't had to go back and mess with it after the repair? ALso... I couldn’t tell where you put the zip tie?

https://uploads.tapatalk-cdn.com/201...e0ef8b8e0a.jpg
• Yellow points to the zip tie. (It's wrapped around the post inside)
• Red shows the direction the zip tie pushes
• Blue shows the force of the fulcrum
• Green shows the resulting force up on the o-ring side to prevent the design flaw to repeat

Teflon tape was to repair the non o-ring seal (other design flaw: a flare made of plastic with no way to add compressive force that gets a D- guys who the hell approved that design!


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https://www.realoem.com/bmw/enUS/sho...diagId=16_0460

Looking at realoem tells me the O-ring is PN 16116761645, about $2.50 at dealer.
Size 22x2 mm.

Thanks. I think It was posted on the fuel pump thread the o-ring size but illogically not here.


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I have a theory as to the root cause...

Somehow the O-ring shrinks a bit (? Ethanol, ? Other chemical, ? Normal aging of rubber BUNA etc.)...then the pressure from the return fuel (probably around 30 psi in the return line) pushes the O-ring out of its groove ---> reducing the flow necessary for the Venturi effect to work.

Siphon pump DIY repair
 

Negative. The plastic twists over time.

https://uploads.tapatalk-cdn.com/201...e0ef8b8e0a.jpg

Refer to this photo, without the zip tie, the bottom piece will rotate clockwise since the force down is only on the right (opposite of Green arrow)

It can twist far enough that the o-ring will push out of its seat.

All that is needed to prevent this is some counter force to the force twisting clockwise, the zip tie does the trick and is a permanent solution.

So I have another question... in this screen cap I circled in red where the zip tie goes. But does it just loosely sit around the odd shaped part? Does it need to be tight? Seems like it would act as a buffer for the connection not to move back and forth if that’s the case, is that why you used the zip tie because it’s such an obscure shape and there isn’t anyway to create an spacer for it? Also in the green circle, am I missing a picture step? Please advise.

http://i284.photobucket.com/albums/l...stekrkq1g.jpeg

I think it's the latch (head) on the zip tie that is doing the job here. It stops the lower section moving up (pivoting) and sitting wonky....