Transit connect won't start
 

I'm going to have a look at a transit connect on a 55 plate with a starting problem.
All lights come on dashboard when the key is at number 2 position but when you go to start it they all go out as though it's a flat battery but even with a jump pack on won't start.seems a posible earth immobiliser problem anyone any rough ideas or can that be by passed to at least turn engine.