On Saturday, February 4, 2006 at 5:36:43 AM UTC-5, damyth wrote:
Mike Jacoubowsky wrote:
I've got a cool little Wrench Force floor pump that will accept
Schrader or Presta. I've used it for over a year exclusively to
inflate my Presta road tubes. Got the kids bikes for Christmas, pumped
them up (Schrader valves), and now (several weeks later) the pump won't
blow air out the Presta hole any more. It's supposed to be "auto
sensing". Is it just buggered? What would you all try to debug this
problem?

It's a fairly common problem with the one-head pump designs. You can often
get it to work if you strike the head against the ground pretty sharply,
which unsticks the internal gadget that detects which valve is in use. But a
new pump hose will probably take care of the problem too, and it's quite
likely to be considered a warranty issue.

As others have mentioned, this typically happens only when there's zero air
in the tube, so inflating just a tiny amount with a hand pump will usually
work. Someone else suggested blowing a bit of air into the tube by mouth,
but I've tried that a couple times without success.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

There is no need to hit anything on these chucks. Simply cover the
valve hole that you intend to use with your thumb, and start pumping.
The back pressure will "free" the valve to the correct postion. You
can then mount the chuck on the tube valve (even if there is no air in
the tube) and start pumping successfully.

Thank for taking the time to post the tip.
It is appreciated.