Volkswagen: 1977 VW bus, distributer cap, automatic fuel

Question
I am interested in buying a 1977 VW van for $5000.  The owners say it is
automatic, fuel injection, with a recently built catalytic converter to pass
smog. One problem they have is that once the ignition key is turned off, the
engine continues to run.  They physically open the engine cover and
disconnect a wire from (here I lost him) the distributer cap?  They say the
engine was rebuilt and has 27000 miles on it.  Does this problem sound
familiar? Easy to fix?  More trouble then its worth?  Any opinions would help.  
Thanks.    Wendy Brubaker

Answer
Wendy,
 This should be an easy fix.  I believe there is a bad diode in the double relay; replace the relay.  Otherwise something is connected incorrectly in the circuit leading to the coil.  A good tech should be able to pin this down quickly.

Good luck, Rick