Ok, let's try this again... bloody unhelpful forum software doesn't quote the post being replied to, it seems...
So yes, the pumps in IC2 don't consider the flowing lava or water as actual resources since a fair few versions ago. This was done to prevent infinite lava being pumped into goethermal powerplants from a single lava block. Only static, non-flowing lava and water gets gathered, so the best thing to do (assuming you can get to the problem) is drop some sand into the flowing lava and let the miner drill through it. Should work fine after that.
As for the diamonds, could just be bad luck. You don't always find loads in random spots, it's possibly better to go hunting for them in caverns yourself. More fun that way too!