Inertia Switch Integration

[JOP33]

The Holley Sniper EFI instructions state to go directly to the battery for power on the fuel pump and EFI computer for clean power (it has its own relay and fuse inline), if I do this doesn’t it bypass the inertia switch then? How should I keep the power clean & direct as suggested while integrating the inertia switch? Or am I missing something else here?

Thanks

[TexasAviator]

Wire the inertia switch between the fuel pump wire coming from the ground and the wire going to the pump itself. This way if it trips you don't lose power to your efi system but power is cut to the pump. I have a similar aftermarket efi system.

[Papa]

The Holley Sniper EFI instructions state to go directly to the battery for power on the fuel pump and EFI computer for clean power (it has its own relay and fuse inline), if I do this doesn’t it bypass the inertia switch then? How should I keep the power clean & direct as suggested while integrating the inertia switch? Or am I missing something else here?

Thanks

I'm not an expert, but I just spent a lot of time discussing a similar question for my FAST XFI Street EFI. What I learned is that the inertia switch wiring is a ground from the Ron Francis fuel pump relay. With the switch depressed, you complete the ground circuit and if the switch trips, continuity to ground is lost thereby turning off the fuel pump. The FAST XFI Street provides a fuel pump control wire that essentially establishes or breaks continuity to a ground circuit (negative control). For my system, I'll connect that negative control wire to the chassis ground side of the inertia switch. This way, the ECM is controlling when the pump runs by completing or breaking the ground continuity to the fuel pump relay and in the event the inertia switch ever gets tripped, it will do the same and shut off the fuel pump. I don't know how the Holley system works, but this may still offer you some useful information. I would think you could just take the relay-side wire from the inertia switch and connect it to the ground wire going into your EFI's fuel pump relay.

Dave

[JOP33]

I'm not an expert, but I just spent a lot of time discussing a similar question for my FAST XFI Street EFI. What I learned is that the inertia switch wiring is a ground from the Ron Francis fuel pump relay. With the switch depressed, you complete the ground circuit and if the switch trips, continuity to ground is lost thereby turning off the fuel pump. The FAST XFI Street provides a fuel pump control wire that essentially establishes or breaks continuity to a ground circuit (negative control). For my system, I'll connect that negative control wire to the chassis ground side of the inertia switch. This way, the ECM is controlling when the pump runs by completing or breaking the ground continuity to the fuel pump relay and in the event the inertia switch ever gets tripped, it will do the same and shut off the fuel pump. I don't know how the Holley system works, but this may still offer you some useful information. I would think you could just take the relay-side wire from the inertia switch and connect it to the ground wire going into your EFI's fuel pump relay.

Dave

Sounds very similar to the Holley set-up. Thanks guys for the input.

[kraftee]

On another note, make sure to mount your inertia switch somewhere that you can fairly easily get to it. When my in-tank fuel pump failed (due to bad connections in the pump itself), my first assumption was that somehow the inertia switch had tripped. Fortunately, I mounted mine just under the right side cowl access panel. So it was easy to check - and figure out that wasn't the problem.

[jimmish]

I saw here that the factory harness was wrong on the inertia switch, that you should use the center terminal instead of the 2 outside terminals?

[JimLev]

I saw here that the factory harness was wrong on the inertia switch, that you should use the center terminal instead of the 2 outside terminals?

My switch only has 3 terminals with the wires connected to the 2 outside pins, these are the correct pins to use.

[TexasAviator]

good follow up. I used a factory switch from a ford mustang and oriented it upright and wired it using the terminals specified by ford. I grounded one switch wire and the other wire went to the pump ground. Ii thank you all for setting me straight on the wiring.