I'm the proud owner of this delightful BX Meteor 19D Auto. Delightfully slow!

Now, it had a nasty immobiliser fitted. This was a simple affair that just was just spliced into the fusebox into a wire that seems to activate the glow plug circuit and the stop solenoid. It looks like someone had been in there before and half removed it, which makes things a bit confusing, as there's a few wires that are no longer connected. There was one other wire spliced in, that according to my continuity testing, was connected to nothing. There was only one immobiliser chip, and the connections on it are very dodgy, so I did what any sensible person would do and got rid if of it, and spliced together the original wiring.
Now it starts like a champ, the glow plug circuit is much more reliable, but it cuts out after 1 second or so of running. Stops dead. No spluuter, nothing. This is accompanied by a relay click, which led me to believe that the stop solenoid relay is cutting out. Sure enough, this was verified by feeding 12v directly from the battery to the stop solenoid, at which point it runs happily. Curiously, when I bridge the stop solenoid to 12v, it also activates the glow plug circuit- not sure if that's normal.
I've used a jump lead to connect the engine to the negative terminal to rule out a dodgy earth. I guess it'd possible that the immobiliser chip has a transistor or something in it that is behaving differently when it has 12v, therefore my continuity tests aren't telling the full story, and I'm missing a connection somewhere...
Any ideas??!