Help needed with fuel system cutout.

Hi all,

I have asked this question before in a different way, and thankyou for the assistance received at the time.

I am installing a 2 point immobiliser into a 1996 Nissan 200sx - I think you call them 240sx or Sentras in the US, Have connected the Primary point to the starter motor - used the diagrams off this site, and verified same :-) For some bizzare resason, the engine still starts when the unit is armed?? When I cut the wire initially, the key was turned and nothing, I hooked it all up and bang, she fires even when the system is armed????

The second point was to go to the fuel system - I wanted to go to the main ignition but the installation instructions say to NEVER use this point? Any reason why?

I finally got a reliable ECU diagram which shows me the pin out for the fuel pump relay - It is titled fuel pump ground wire. Is this the wire I am looking for for the 2nd cutout point?? I'm assuiming that if I cut this, the fuel pump won't work, hence immobilising the vehicle.

Any help much appreciated.

Remember that anything you do, you must test first and you do at your own risk.

That said, it sounds like that wire would work for your fuel pump kill switch. You should remember that once these relays lose power, they no longer function, so if a thief were to unplug the alarm or cut the power wire to it, they would bypass any kill switches, unless of course they are normally open, but then you really dont want to be using a normally open fuel kill switch because that would be putting a lot of confidence in a single relay since it would be working the entire time the car would be running. I am not necessarily trying to convince you that you dont need a fuel pump kill relay, but I dont view them as any more beneficial than a starter kill relay or an igntion kill relay since they are disabled by taking power away from the alarm, which can be done quite easily by a good thief (I am not speaking from experience, But being an installer I certainly do have to think about how I would steal a car if I wanted to). The thing I have the most confidence in is my 2 way alarm, because as long as I am in range, I will get a fair warning that someone is messing with my car. I dont even use my siren unless I know I am going out of range (I have a switch on it to turn it off).    

Nevertheless, you should fix your starter kill feature first. Are you aware that you have 2 starter wires? You should test all of the heavy gauge wires in your ignition harness to make sure of the function it serves, especially since there are typically slight differences when comparing vehicle wire databases.

For the 200sx and for the Sentra as well, I show the 2 starter wires are BLACK / YELLOW, and BLACK/ Blue.

For the 240SX I show they are BLACK / YELLOW and BLACK/ White.

Both wires need to be cut and relays installed for the starter kill feature to work. I have also not seen any notes that say Not to use an Ignition kill switch on that vehicle, but that doesn't mean that the source you used that mentioned that was wrong.

Keep us posted if you have any questions.


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J Rilla

Owner/Installer