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Discussion Starter · #4 ·
I had a couple of members asking for the instructions for the cut off switch.

Here are the instructions I used:

Parts Required:
15A, 30VDC DPDT relay, Radio Shack part number 275-218c, or equivalent. The relay should be able to handle 6 amps or so at 12VDC.
There is a matching socket: Radio Shack part number 275-220.
Misc electrical connectors and wire.

Procedure (from Steve Das ):
1. Fabricate a bracket for the socket and mount it behind the glove box, on the upper right corner of the AC plenum. There is a hole already there and the bracket should bolt right to that hole. This position is close to the fuel pump wire (which runs behind the right kick panel just below this location) and is very accessible. Mounting the relay here resulted in very short wires to the fuel pump wire.

2. Before starting this modification, pull the Air Bag fuse and separate the TWO yellow Air Bag connectors under the steering column just to be safe.

3. Locating the fuel pump wire: There is a large, black connector behind the right kick panel. The connector you are looking for is "bolted together". It has a bolt running through it to hold it together. The wire you want is a large gray wire in the center of the connector. Rather than try to describe it. The numbers on the connector are duplicated and make no sense, locate it with a test light. The wire you are looking for has 12 volts applied for 2 seconds when you turn the key on but don't start the engine. Once the wire has been located, you are ready to start.

4. You can either cut this wire or pull it from the connector. I cut mine. The wire from the engine compartment will have 12 volts on it as described above. The other wire will now be dead.

5. Layout of Radio Shack # 275-218c Relay terminals:
1. Normally closed fixed contact #1
2. Normally closed fixed contact #2
3. Normally open fixed contact #1
4. Normally open fixed contact #2
5. Movable contact #1
6. Movable contact #2
7. Relay Coil

6. Using wire of sufficient size for the current required, connect the wire from the engine compartment to pins 3 & 4 (normally open stationary contacts) of the relay.

7. The wire from the pump (the other cut end) goes to pin 6 (one moving contact).

8. Connect a wire from pin 5 (other moving contact) to pin 8 (one side of the coil).

9. Connect a wire from pin 7 (other side of the coil) to a good ground: there is a ground lug just in front of the door opening at the bottom.

10. Now determine where you want to mount the hidden push button switch. It should be some place not too obvious but easy to get to. Let your imagination be your guide.

11. Run wires from the Normally Open contacts on the push button switch to pins 3 & 8 on the relay.

12. In addition, you can put a hidden toggle switch (a "valet switch") across pins 4 & 6 of the relay. This allows you to defeat the relay should you need to leave the car with a parking attendant, take it in for service, or drive it if the relay fails.

13. Keep in mind that the wires you splice to the fuel pump wire must be large enough to carry the fuel pump current of about 6 amps. If you use a hidden toggle switch as a "valet switch", those wires as well must be large enough for 6 amps. If you wire this correctly, the wires to the hidden push button need only carry relay coil current (about .075 amp) so they can be smaller. Be sure you know what you are doing with your wire size.

14. What all this does is this; when current is supplied to the relay by turning on the key, and the push button is closed, current flows through the push button and powers the relay coil. The relay closes and one set of the relay contacts supplies current to the pump and the other set supplies current to the relay coil, holding the relay closed. When the current disappears as a result of shutting off the engine, the relay opens and current is prevented from getting to the pump until the cycle is repeated.

15. Remember that there is a switch in the oil pressure switch that supplies current to the pump as well (in the event that the fuel pump relay under the hood fails) but that connection is ahead of this point so this system still works.
I hope this hasn't been too confusing. I can, of course, assume no responsibility for your installation but if you are careful with your wiring, insulate everything, use heat shrink tubing on your wire splices etc., you should have no trouble.
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