Pump question

[Steve]

I've acquired an old Blackburn frame-fit pump, and however careful I am to connect it to the valve (Presta), I find air always finds its way back out of the tube into the pump, so I can never get it near the required pressure.
Is there a valve in the pump itself, which could be faulty, or might there be another explanation?

[Mike Sales]

I've acquired an old Blackburn frame-fit pump, and however careful I am to connect it to the valve (Presta), I find air always finds its way back out of the tube into the pump, so I can never get it near the required pressure.
Is there a valve in the pump itself, which could be faulty, or might there be another explanation?

Perhaps you need to push the pump head further onto the valve, so that the rubber washer does not bear in the little knurled nut.

[mjr]

There's not usually a second valve in the pump, although some have one.

The most likely cause is something is keeping the tube valve pressed open, stopping it from closing while the pump is connected. Possibly the valve core is bent, or possibly there is some obstruction in the pump connector, or possibly your valve core is simply longer than the old pump's designer expected (you might be able to bodge it by undoing the valve nut a little less than fully, if the pump is hitting the nut rather than the post), or it could be something else entirely!

Happy hunting!

[freiston]

I don't know what the Blackburn pump head is like and I hope I'm not teaching you to suck eggs but one push-on pump that I have has (as well as a reversible rubber grommet to convert the head from presta to schrader) a plastic insert behind the rubber grommet that also has to be reversed - could it be something like that? Otherwise, I suspect a bent core, the pump head not pushed far enough over the valve, the pump not being held "straight" or a combination of the last two.