I doubt you're out-powering the quarry with that configuration...
Come to think of it, I had this problem too. The conclusion I came up with is that there is a sort of maximum throughput for non-wooden conductive pipes (even gold ones) so when you serially chain these, they don't work as expected for large power draws. I'm not sure if this is the actual mechanics but it seemed to be a consistent interpretation. Conductive pipe behaves very strangely when you make cycles or T-joins. The easiest solution I've found is to use a single piece of wooden conductive pipe and attach numerous engines to it in a star configuration. It's ugly, but the throughput of a single piece of wooden pipe seems infinite.
Eventually I had the infrastructure of upgrade to redstone conductors from TE and I've not looked back. Pipes just aren't suited to power networks as they stand, and they seem to lose more power than the wiki suggests they should.