rugby6or7

Hi - can you help me?,
We have recently fitted a 1.8 Gti engine from a 2002 Satria into a 2006 Jumbuck, the engine has a Mitsu ECU and the Jumbuck a siemens, we had no luck getting the engine to start (or even crank) with the combination of wiring, so we bit the bullet and changed all the looms - engine, dash and righthand side section which goes through the bulkhead/wing.
Everything plugs in except the fuel pump but we identified the correct wires and corrected them.
All works and it cranks but still won't start!! - I suspect the immobiliser - we have the car's ecu, immobiliser and (triangle) key (the car ran before we started) - we have dash lights but no check engine light and no small led near the key which should light up when you put the key in, I think these problems are linked but have checked and double checked everything.
I thought an immobilser fault would just knock out the fuel pump/injectors but wonder if it is stopping the led/check light powering up - don't understand why as we have all the matching components - please help if you can as I am tearing my hair out !!!!!!!
Thanks
Richard.

I noticed the post about siemens ecu wiring and wondered if anyone would be kind enough to help....
I am in the UK and have put a 2002 4g93p from a Satria GTI into my 2006 Jumbuck - all is in and plugged together but nothing on the key - I get lights but no cranking - I have looked at the two plugs that go onto the dash loom near the ECU and seen many differences in wire colours/position - the truck has a siemens ecu and the doner gti a mistsu one which we have fitted with the engine loom - it has a triangle key which I think means it has an immobiliser in the mitsu ECU?
Do you know if/how I can swap the wires in the plugs to make it right or do I need to change the dash loom? - I am worried about this as it seems to also power rear lights etc etc which may be different between the car and the truck.
Any help gratefully received.

Regards
Richard.