Inertia Switch Installation

[Lynn Miner]

This “How To” provides for the installation of a fuel shutoff inertia switch. Steve Cioffi (P2125) deserves the credit for the research in finding the parts from Pegasus Racing.

In the event of an accident, this switch opens due to the force of impact and deactivates the fuel pump electrical circuit so that the flow will stop. This is of obvious importance in the event of a crash. However, in racing applications a significant bump can actuate the switch knocking you out of the race. This has been discussed on the forum at length debating the pros and cons. I'm a poser (and not ashamed of it). I also know how difficult it would be to exit the car in a fire not to mention my wife or other passenger who would likely freak out at getting smacked let alone the potential for a fire. I view this device as a required piece of equipment on a car like this.

There are a number of possible locations to mount the switch. I chose to mount it on the driver’s side of the rear bulkhead just in front of where the fuel pumps mount. This location provides easy access and service. In this location, I have yet to have a false trip due to bumps etc with 1200 miles logged to date. What ever location you select, the switch MUST be located vertically on a solid panel as shown.

In the photos shown below, one can see that dielectric grease has been applied to the connector. This prevents corrosion of the contacts from water. Further details are found elsewhere on this site discussing techniques associated with electrical wiring and preventative measures.

I made a label to indicate the location because the switch is not obvious when the pumps are installed.

The wires could be connected to the pumps at this location but I prefer to run the wires to the source. This complicates things a bit but it is a technique I prefer from an engineering standpoint. Do as you feel appropriate. The wires were shrink tubed and run along the floor pan and wire tied to the brake line.

The wires are then run up under the dash and connected to the fuel pump switch.
The supplied label is then placed to the left of the fuel pump switch as below. Make sure you reset the switch.

Scott Calabro from Tornado sent me some additional thoughts on this How To that are something else to consider.

It would be infinitely better in an accident to stop all electrical power than just fuel flow from the pumps. Taking away the potential ignition source as well as fuel is a better solution. his can be done the same as your pump shut off. The difference being that the g switch would control a relay capable of carrying the entire electrical load of the vehicle, including starting loads. When activated the entire elec. system would be shut down. This relay could also have a manual on/off switch. It is very simple to do.