Don't pump it up at all. Let it sit overnight.

The problem here is that you likely have a smallish tube volume, so when you air it up the patched area and surrounding tube stretch at different rates, which act like peeling tape off something at an angle. If the patch is large enough and the bond good enough, you may be able to inflate the tube without the bond failing all the way back to the tear.

Using the thinnest possible innertube as a patch will also help to minimize that difference in stretching.


Obviously, you could also just replace the tube. But it is an interesting problem.