Which Circuits to Immobilise?

Guru Meditation · Post by **Guru Meditation** » 05 Feb 2004, 19:32

I am about to buy an immboliser for my 93 ZX td aura and do a DIY job on it (you may have seen my earlier query about alarms). The immobliser I have my eye on is a Microscan transponder two circuit immobliser, 30amps per circuit.
Question is, which circuits do you immobilise on a diesel with no ECU?! The starting circuit is one ie the starter motor, although I don't know if 30amps is enough for the starter motor. But what other? I'm thinking perhaps the ignition eg immobilise it behind the bulkhead so it is not possible to hotwire it from within the cabin-I don't think the car will run if the ignition is off and the car was push started?
I am not totally au fait with how immobilisers are wired in so I may be way off the mark?

Post by **RichardW** » 05 Feb 2004, 20:02

On a diesel there are only 3 circuts you can immobilse:
Starter - supply to activate solenoid is pretty small, when solenoid closes internal contacts carry the heavy current the motor needs.
Glow plugs - there is a light weight relay that activates the heavy weight glowplug controller.
Fuel cut off - this is on the end of the pump - low current device which is what is used to stop the engine normally. It is this device that is used to immobilise the later cars that are factory fitted - but they have a tamperproof cover over the solenoid.
It is all too easy to start one of these diesels:
+ve wire to the solenoid to activate it, jump lead onto the glow plugs for 10s, then jump lead onto starter terminal and away you go. If any one wants to be away with your ZX and they know what they are doing, they will be, immobiliser or not!

Guru Meditation · Post by **Guru Meditation** » 05 Feb 2004, 22:24

I had never thought of it like that, never realised how easy it was to nick the thing. Need to get a lock on the bonnet.

wheeler · Post by **wheeler** » 05 Feb 2004, 23:55

you would be lucky if this stopped a reasonably good theif for more than 3 minutes,for a diesel with no ECU you really need a diesel imobiliser with a solenoid valve that cuts off the fuel in the pipe,if you can get a seperate valve you could use the imobiliser to pilot a relay to control it.

sooty · Post by **sooty** » 06 Feb 2004, 00:46

Good idea about the solenoid, but where would you get such a valve and to be diesel proof, ie: not perish.

alan s · Post by **alan s** » 06 Feb 2004, 02:59

The second solenoid's a great idea; just a thought, but if you fitted such a thing, if fitted at the rear of the car near the fuel tank with a key type switch in the boot should make life pretty hard. I knew a guy who had a similar system in a petrol car worked off an electric fuel pump.
Option #2 :- Do a Mr Bean & take the steering wheel with you; that fools 'em. [:D][:o)]
Alan S [:p]

nick · Post by **nick** » 06 Feb 2004, 03:16

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by alans</i>

Option #2 :- Do a Mr Bean & take the steering wheel with you; that fools 'em. [:D][:o)]
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I was going to suggest removing the battery and timing belt whenever you leave it parked anywhere [:o)]
Nick

Guru Meditation · Post by **Guru Meditation** » 06 Feb 2004, 04:43

Sounds like you're right on to something with that idea about fitting an inline solenoid operated valve, you could use the two circuit immobiliser to immobilise the starter motor circuit and the inline valve. The valve would be tucked away near the bulkhead, possibly only accessible from underneath. Question of finding a suitable valve-surely wouldn't have to be anything too elaborate just spliced into the fuel line with all it's associated electrics all waterproofed up etc.
Where would you get a solenoid operated valve of sufficient spec for constant diesel immersion?

alan s · Post by **alan s** » 06 Feb 2004, 05:13

They used to use a very simple one on the early Mazda E2200. That was the one that they reckoned had a copy of an old Perkins Diesel fitted to it.
Alan S

AndersDK · Post by **AndersDK** » 06 Feb 2004, 12:18

I like the idea with this extra elektrovalve fitted in the fuel line. Must be fitted as close as feasable to the rotopump - to have as small as possible fuel supply resting in the fuel lines AFTER the valve.
As suggested fitted out of sight when bonnet first opened - i.e. down on the footwell sheeting where the fuel lines bends up from under the car.
First place to look for a suitable valve would be at diesel specialist garages.
Anyone knows about these "mysterious" cap covers for the battery + pole seen on more recent cars ?
Have noticed these caps makes it impossible to reach a feed point from the battery + pole ?