The intent
of this page is to provide ideas that you may use for your own alarm
system. It's not intended to give exacting instructions or to tell
exactly what has been done on my car.
The page will remain a "work-in-progress"
for quite some time.
A fuel pump "disconnect"
circuit;
I worked up a circuit using three standard Bosch
relays that can be used to disconnect the wire that goes to the fuel
pump. It could also be used to disconnect the wire that goes to the
distributor, among other possible areas. The relays are Bosch number
332-209-151.
I'm planning on hooking up the circuit to my
car alarm (yet to be installed) so that the "grounding" outputs
that work the door locks, also work the "disconnect" circuit.
Un-locking the car (using the alarm) allows the fuel pump to work. Locking
the car sets the circuit so that the fuel pump wouldn't work.
The "trick" thing about the circuit
(and what makes it worth doing) is that if power is removed, the circuit
defaults to "disconnect" mode. Even after the battery
is reconnected, the circuit remains in "disconnect" mode until
the alarm "unlocks" the car.

For the circuit to work, you have to splice into
the wire that goes from the ECU and to the fuel pump.
If you don't have an alarm, you could use two
momentary switches to "enable" and "disable" the
circuit. The switches should have ground on one side. Mount the switches
in different locations and even if somebody sees you using the switch
you use to activate the circuit, they don't know where the other switch
is located.
You could use the "disable" switch
as a "panic" button if you thought that you were going to
get "jacked" (a term that is hard for me to use due to my
age).
If you hooked up the circuit to a "switched
12 volts", the circuit would go to "disable" every time
that you turn off the car. You would then have to hit the "enable"
switch after turning on the ignition.
The circuit does not have to be mounted where
the main alarm unit is. This is helpful if the thief thinks that just
removing the alarm will help get the car to start.
When the circuit is in "disable" mode,
all relays are turned off and as a result, they don't consume any electricity
that could drain the battery. When in "enable" mode, only
two of the relays are energized.