Sometime ago, I inquired about antitheft devices for the vanagon (diesels).
Amazingly, I saw this in the newsgroup alt.revenge.  It seems that this same
idea could be used on the diesel vanagons on the fuel pump, I think.  
(I edited the header a bit to shorten it here)
Stuart Hutton
> From: tline@iglou.iglou.com (Tom Line)
> Subject: Re: carthieves
> 
> ---------------------
>                      |             circuit breaker amperage
>                       -            should be higher than normal
>     COIL ON CAR        |          current amount for the red wire. 
>                       -
>                      |                     ADD               12v normal
>                      |* red wire --*-(CIRCUIT BREAKER)-------
> ---------------------              |
>                                  (TOGGLE       (hide breaker and 
>                                   SWITCH) switch under seat?) 
> WHEN TOGGLE SWITCH IS CLOSED        | 
> CIRCUIT BREAKER BLOWS DISABLING   vehicle chassis 
> THE COIL.                          (ground)
>   
> -- 
> 
> 	The AMAZING TOM LINE!
> 
>