imoboliser on ford escort van (changed deisel pump )

[manvan]

hi all i have a ford escort 1.8 diesel van T reg idleing very ruff using lots of deisel so the man in the garage told me to change injectors. still the same so he then told me that i needed a new pump so i change the pump with a second hand pump only to find out that the pump is part of the P.A.T.S IMOBOLISER.The van will not turn over any more as soon as i pluged the old one back in the imobilser reconised the pump and turned over can any help or know a way around this problem