How to add delay when activating a pool member

The best place for a requirement like that is in iControl. A possible iRule solution could be handled by measuring the time of failure on server one, then checking to make sure 5 minutes has passed, then up server two and reset the failure variable back to 0. You need to be on a 9.2 version, and someone else might post back on a better event to place the checking other than CLIENT_DATA. I usually only use the HTTP events, so I'm unclear what's best for not HTTP traffic.

when CLIENT_CONNECTED {
  set failure 0
  set time_failed 0
}
when CLIENT_DATA {
  if { $failure } {
    if { [clock seconds] > [expr { $time_failed + 300 }] } {
       LB::up pool yourPool member 2ndServer yourPort
       set failure 0
    }
  }
}
when LB_FAILED {
  set failure 1
  LB::down pool yourPool member [LB::server addr] yourPort
  set time_failed [clock seconds]
}

This is untested! It might not work, but maybe it will get the wheels turning for you...

thanks for your posting, the traffic is tcp 1526, so the events should work.