Inertia shut off circuit ?

MartianBob

Registered User
I'd like to put a manual switch in to shut off my fuel pump for theft purposes.
Is the inertia switch in the trunk part of a relay circuit on 94/95 SC's?
Can I simply splice one of the wires going into the inertia shut off and wire a toggle to it?

Thanks for any advice
Bob
 
There should be a decal on the trunk liner material on the left inside of the trunk that mentions the fuel safety shut-off switch.

Pull the trunk liner away from the body until you can see the switch and the harness leading down and away. There will be a relay on the harness.

Disconnect the harness and probe the connector to locate a key-on hot.

Instead of cobbling in a toggle, why not just use the safety switch? All you have to do is open the trunk and smack it to shut off the circuit - then when you return to the car, simply do a reset.

Unless you hide it well, perhaps making more trouble for yourself, a thief can toggle a switch same as you...
 
I'm sick of popping the trunk and hitting the switch with my torque wrench for a variety of reasons. I was planning to conceal the switch.
 
KMT, the fuel pump relay is part of the IRCM on late models, it's not in the trunk. I'm guessing the pump is not being powered through the inertia switch (not positive though).
Has anyone else done this on a 94/95 car?

Thanks
Bob
 
KMT, the fuel pump relay is part of the IRCM on late models, it's not in the trunk. I'm guessing the pump is not being powered through the inertia switch (not positive though).
Has anyone else done this on a 94/95 car?

Thanks
Bob

I didn't say anything about a fuel pump relay as I recall.

Early models have an IRCM (behind the passenger side headlight) with relays for the EEC and fan.

Different relay at the inertia switch and all years have the same inertia switch to my knowledge.
 
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Bob,

You can splice into either wire going to the inertia switch and add a toggle switch and it will work just fine.

-Rod
 
>You can splice into either wire going to the inertia switch and add a toggle switch and it will work just fine.

Circuits that include relays do so for a purpose, which is to use a low current circuit to trigger a higher one, thus keeping the higher one as short as possible.

Casually tapping into either wire at the inertia switch, and then running that current further by adding more wire and another switch, risks ignoring the original intent of the relayed circuit and isn't recommended. Don't ask how I learned that :)
 
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Bob,

Sounds like it would be much easier to wire a switch into the ignition, but I can't help wondering why you just don't have an aftermarket alarm installed. A hidden switch like your talking about might stop the repo man, but it's not going to stop someone from breaking into the car.

David
 
Casually tapping into either wire at the inertia switch, and then running that current further by adding more wire and another switch, risks ignoring the original intent of the relayed circuit and isn't recommended. Don't ask how I learned that :)

Where is this relay in the circuit? On a 94 SC, I see circuit 787 come from the EEC and CCRM, spliced into one wire, which runs through a few connectors until it reaches the inertia switch. On the other side of the switch, circuit 238 goes directly to the fuel pump through two connectors.

Either way, that circuit is not carrying much load. As long as Bob seriously taps (as opposed to casually tapping :D ) into either wire and is smart about both the gauge wire he uses and his connections, it will work just fine.

-Rod
 
Where is this relay in the circuit? On a 94 SC, I see circuit 787 come from the EEC and CCRM, spliced into one wire, which runs through a few connectors until it reaches the inertia switch. On the other side of the switch, circuit 238 goes directly to the fuel pump through two connectors.

Either way, that circuit is not carrying much load.

If that circuit was 'not carrying much load', it wouldn't be designed to include a relay.

There are two wires at the inertia switch: Pnk/Blk & Drk-Grn/Yellow

The Pnk/Blk wire leads to the inertia switch, away from the adjacent relay. The Drk-Grn/Yellow wire carries power out of the inertia switch to the fuel pump. The fuel pump is then grounded via a black wire. The fuse before the relay is spec'd at 20A.

Hacking into either the Pnk/Blk wire or the Drk-Grn/Yellow wire will mean re-routing the electric fuel pump current load via additional wiring and a switch.

To use a lightly loaded circuit, it is best to interrupt the relay trigger feed and not the pump feed.

These cars have enough issues w/the electrics - why risk adding more?

As David says, why not just an alarm system, but hey, it's not my car and not my neighborhood. But there does seem to be humor in thinking about a car thief driving a car that's on fire...

Ken
 
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Couldnt ya do something like put a lock through the clutch arm....They then would have to find the lock and cut it.Or hot wire it in gear......Adjust the seat so far forward that the average theif would get ticked cause there wasnt enough room to work.....Remove the shifter or mod one that unscrews....Put a block out plate on the exhaust....Similiar to the potatoe in the exhaust.......I like to do the sneaky way myself....Removable racing steering wheel....

F1
 
Ken,

I agree that it's best to interrupt the trigger wire on a circuit with a relay, as the whole point of the trigger wire is to activate the relayed circuit. I just don't see a relay in that circuit on a 94 SC.

BTW, the Pink/Black wire is circuit 787 and the Dark Green/Yellow wire is circuit 238.

-Rod
 
I definetely don't want to put a switch into that part of the circuit that carries the service amperage to the pump, I thought the inertia switch was on the trigger side of a relay already integrated into the circuit.
Sounds like I'll have to add another relay to either wire of the inertia switch to do this properly.
A car alarm would be great were it not for false positives.

Thank you for the well researched responses.

Bob
 
>A car alarm would be great were it not for false positives.

Sounds like a valid concern to me - good luck w/your project.

Ken
 
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