Immobilizer using vacuum circuit?

[Zanimat]

I have a 1988 300D auto and want to improve the security by disabling a part of the vacuum circuit by means of a N/C solenoid valve which is operated by a hidden switch. I was hoping to use the engine stop signal, thinking that it worked the opposite way from how it actually does - now I know better!
Would interrupting the supply to the Vac. control valve on the pump achieve the desired result? Or can anyone here suggest a better alternative? The car is already fitted with an alarm & heavy duty steering wheel immobilizer, but I'd like to make it hard to start even if someone steals the keys.
Thanks in advance,
Malcolm

 

[Bolide]

You might be better off using a fuel feed shutoff. Mercedes sell a non-return valve kit for the W124 diesels which includes an electrically-driven valve. I'd suggest using that with a switch. Kit costs a whopping £10.88, part number is B6 6 54 8198

But bear in mind that most cars that are stolen are picked up with a spec lift and towed away. It only takes a few seconds

Nick Froome
www.w124.co.uk

 

[Zanimat]

Thanks, Nick; sounds like just the thing! Can you give me any clues about where it's normally fitted?
I doubt anyone would go to the trouble of "lifting" my old lady; hardly worth the effort! And having lost my keys soon after acquiring the car, I know how difficult it can be to defeat the ignition lock! However, I like to try & make it as difficult as possible for the would-be thief.
Malcolm