peugeot 306 td immobiliser wont accept new fuel pump?

i have a peugeot 306 td with a key pad immobiliser, i broke down so i got towed back to my garage, slacked off an injector line - no feul being pumped. its possible that the stop solenoid was nakered but it is sheilded. iv have got a replacment pump (locus) the same as origenal. but the immobiliser will not accept it. with the new pump wired up the immobiliser shows green and red and makes all sorts of nagative noises. then i tried pluggin the old pump back in and it goes back to normal?? can anyone help? many thanks to anyone who can . Ellis