Imobilisers are usually pretty easy to remove if you just take your time and don't start cutting through wires at random!
They would usually disable the starter and the fuel pump. It sounds like yours has developed a fault and is no longer connecting the fuel pump when it should. You may be able to fix this and keep using the imobiliser or just bypass it so that it inly imobilises the starter.
It's an after market type so the first thing I'd do would be to find it, find the make/model and get some instructions for it.
Steve


