Joe Blow Sprint track pump woes

I’ve got a 20 year old Joe Blow Sprint. It wasn’t pumping well so I replaced the o-ring on the piston at the bottom of the rod. Sorted for a while but the spring that stops the piston bottoming out rusted away. I took it to bits to clean and grease everything but now it’s not holding pressure – if I connect it to a tyre, pressure leaks away.

Does anyone have an diagram of one or any ideas what the problem could be? I could just buy another one or use my compressor but I’d prefer to fix it.

Thanks,
Murray

I had a similar problem when water got in after I left it out in the rain. Too much grease on the piston causing it to stick?

I don’t have anything useful to add I’m afraid, but interested to see if there is a diagram. I also have a 20 year old Sprint, every time I attach it to a tyre I’m only able to get about 1/4 of a stroke out of it.

Replaced it as I needed to pump things up and didn’t have time to fix it, but will get to it at some point and donate it once it’s fixed.

Mine recently started to leak air so replaced the clamp that attaches to the valve.

I don’t have anything useful to add I’m afraid, but interested to see if there is a diagram. I also have a 20 year old Sprint, every time I attach it to a tyre I’m only able to get about 1/4 of a stroke out of it.

My pump did that it was the o ring being too frictiony and rolling out it’s groove and locking the piston. Undid the top to expose it and dumped in a goodly amount of gt85.

Sorted.

Thanks, will give that a try

Sorted

Wasted more like 🤪

Fixed!

The pump is a big tube and a small tube in parallel. The piston on the main rod is sealed with an o-ring – I’d replaced that as it was worn out. It needs some lubrication to avoid sticking, I used XP222, I should have used silicone grease but I didn’t have any.

There’s a check valve at the bottom of the pump that you get at by removing the alan bolts holding the base to the pump. It’s closed by a really wimpy small spring. I used XP222 on that too as it was very rusty – that’s a problem, the spring’s not powerful enough to overcome the grease. Cleaned it out and lubed with silicone spray.

The check valve sits in an aluminium plug with 2 o-rings that seal against the body. The plug can be removed by unscrewing it. There’s a small hole drilled in between the big tube and the small tube between the o-rings. Air from the small tube can get though it to the gap between the o-rings and hence to the check valve and vice versa.

When you depress the piston, it forces the check valve down and lets air into the plug and then to the small tube going up. Test by putting one finger over the top of the small tube and one in the middle of the plug to seal it and depressing the piston. You should feel resistance. If you uncover the top of the small tube and still have resistance, there’s a problem getting air from the plug into the small tube – fiddle with it.

Next problem was leaking air from an attached tyre. What should happen is that the pressure should go down the small tube, into the bung and push the check valve up. If the previous check works, it has to be a problem at the top of the pump where the gauge etc connects. There’s a little rubber bung with a hole in it that should seal it – but if it’s pushed level with the top of the small tube it won’t. Fit the bung to the plastic top of pump assembly and it’ll stand proud enough to seal.