Would grounding the Tach signal wire  COIL - side mess up the IGN
system? or even interupt it?
just thinking out loud..

Dan

  Greg Potts <greg@POTTSFAMILY.CA>
Subject:

Hi Max,

I doubt that the van would go far at all with that switch installed.
Without incoming fuel available to maintain pressure in the fuel rail
the FI system will quickly fail... probably before there is time to
get the vehicle into gear.

The problem I see with this is that after the attempted theft you
stand a pretty good chance of needing a new fuel pump... running the
pump dry is a good way to overheat it.  Defeating the ignition
instead might be a less costly alternative.

Happy Trails,

Greg Potts