Bike pump that won't pump flat tyres!

[Kumquat]

I have a bike pump that pumps very well up to highish pressures (never gone beyond 80 psi, but it's a damn sight better than my old $2.99 hand pump) BUT it will not pump up tires from flat!
The pumping "action" occurs as normal, but I can hear air escaping with every "pump", which sounds like it is coming from the body of the pump itself, NOT the join between pump and tube, and the tube doesn't inflate.

If I get a puncture I have to start the pumping with old hand pump, and then swap pumps once it's pumped up enough, so I can get enough pressure in.

What am I doing wrong? Help!

 

[fossyant]

Possibly either not on the valve enough or there is a fault with the pump's valve in the air chamber.

 

[Sharky]

With the presta valve lock nut, try with it not fully undone. If fully extended, it might be being pushed back in by the pump and deflating it.

Just a possibility.

 

[deptfordmarmoset]

I've got one tube without a lock nut on it and it's difficult to get the pump head on securely without any pressure in the tube. I wonder whether you're having the same difficulty. I've had to hold the valve down firmly through the tyre to stop the valve moving away so that I can get the pump head on properly.

 

[raleighnut]

I've got a 'twin head' pump like that, it needs back pressure to decide which of the heads to switch to. I just start off with an old Bluemells pump till I've got a bit in.

 

[alicat]

What @deptfordmarmoset says. Press the inner tube (at the spot where the valve is) against the pump until the air starts to inflate the tube.

 

[Chris S]

I have a bike pump that pumps very well up to highish pressures (never gone beyond 80 psi, but it's a damn sight better than my old $2.99 hand pump) BUT it will not pump up tires from flat!
The pumping "action" occurs as normal, but I can hear air escaping with every "pump", which sounds like it is coming from the body of the pump itself, NOT the join between pump and tube, and the tube doesn't inflate.

If I get a puncture I have to start the pumping with old hand pump, and then swap pumps once it's pumped up enough, so I can get enough pressure in.

What am I doing wrong? Help!

I bought a pump like that from Poundland, it was absolute rubbish.

 

[Ajax Bay]

So when you're riding do you take two pumps with you? If riding take the 'hand pump' and it'll give you enough pressure to get home. At home, cut your losses, buy and use a track pump - CRC have the Topeak one at £20 on sale currently.
http://www.cyclingweekly.co.uk/news/latest-news/grouptest-track-pumps-121404
http://www.chainreactioncycles.com/...gclid=CPL8iuDZmsoCFeISwwodcSgLJg&gclsrc=aw.ds

 

[Kumquat]

So when you're riding do you take two pumps with you? If riding take the 'hand pump' and it'll give you enough pressure to get home. At home, cut your losses, buy and use a track pump - CRC have the Topeak one at £20 on sale currently.
http://www.cyclingweekly.co.uk/news/latest-news/grouptest-track-pumps-121404
http://www.chainreactioncycles.com/...gclid=CPL8iuDZmsoCFeISwwodcSgLJg&gclsrc=aw.ds

Sorry, I didn't make it clear, it's a Zefal foot pump, so clearly it doesn't come with me on rides!
I don't really want to buy another one, it's pretty new!

I never carry a pump with me at all because 95% of my cycling is commuting/utility and it would take less than an hour to walk home. But now you mention it, perhaps I should...

 

[Ajax Bay]

Carrying a pump, levers and a tube dramatically reduces the chances of a p**cture. You could replace a tube and be back heading for work 12+ times in the time it'd take you to walk home. And thus equipped you could, Good Samaritan like, help an unfortunate by the roadside if she/he had come unequipped and been unlucky.

 

[Kumquat]

I think my issue could be something like this guy's
View: https://www.youtube.com/watch?v=NN8lzRsIRXY

Except my pump doesn't have 2 exit holes to attach to the valves, it has one that you slide a thing up and down to make it presta/schrader.

When I pump without the inner tube attached, I can feel air coming out of the end of pump where it's supposed to.
If I pump with my finger pressed tightly over the end, making a seal I can feel the pressure and the gauge shows the pressure jump up.
If I put my finger over the the end but don't press quite tightly enough then I can feel no air attempting to come out of the end, although I can hear the "shh, shh" of the pump when I pump it. (which is actually nearly silent when it's successfully pumping)

I think therefore that the pump needs quite a lot of back pressure to work? Not sure why, or how to fix it. Please help!

 

[Kumquat]

Please excuse the blurriness of photos, Even in 2016 some people are still using a brick phone