Leaky fuel pump union.

[Mike Ruddy]

My car's a '59 T2 and I have an intermittent fuel leak from my fuel pump. Whenever It happens, which is every coupe of months or so, I tighten the union and all is usually well for a while but I'm hoping for more of a permanent solution.

Here the union partially undone, the 17mm fitting has a red fibre washer and the 14mm pipe fitting doesn't have any seal at all.

Is this correct ?

[C J Murray]

It is not normal for those joints to loosen. The fitting gets a good snug and then the compression nut on the line gets a more energetic tightening while holding the fitting with a wrench to avoid over tightening the fitting into the aluminum pump. Once the compression nut is firmly tightened the fitting and the compression joint can not move. Your can put some sealer on the threads of the fitting but the fiber washer is normally all that is needed.

[Mike Ruddy]

Thanks CJ, taking it to pieces has helped me see how the union works, I am cautious about over tightening but all the parts seem to be there according to PET so I'll nip up the fitting and tighten the compression fitting as you say and see how we get on. Thanks.

[David Jones]

Mike, sometimes you run out of thread on the nut (item 40) because the compression fitting has been compressed beyond it's capabilities so the only option is a new compression collet and a slightly shorter fuel line after you cut it off.

[Martin Benade]

I never needed a new collet. Is it easily available?

[David Jones]

Stoddard, though as I remember I used a brass collet for an American 5/16' fuel line compression fitting.
https://www.stoddard.com/539-08-206.html

[C J Murray]

Compression sleeves also come in different lengths to fit different length compression nuts or different length male threads that result in differing amounts of space for the sleeve. If you install a short sleeve where a longer sleeve is needed the sleeve may not be clamped sufficiently to seal the joint before the nut bottoms out. To test for this condition tighten the compression nut and see if you can rotate the pipe. You should not be able to move the pipe in the compression joint. In the US, hardware stores and some auto parts stores sell compression unions and parts. Take the pipe to the store to see if the sleeve fits your pipe.

Usually when the sleeve is a problem the joint will leak always and not loosen up in use.