Inertia Switch. Anybody?

MileHighMan · Post by **MileHighMan** » Fri Sep 15, 2006 9:45 pm

Hi again guys. I have a question about an inertia switch in a race-car. Does anyone sell one? I know I can buy one from the ford dealer, but ,does anyone know if an aftermarket company makes it? We had a racer crash, and burn, and die, in the last 2 weeks. I talked to a guy that was there, and he said that the guys car flipped, and windshield popped out, and the carb broke off, and fuel sprayed all over the racer. Burned bad. I have a electric pump in my car, and in case of emergency, I want it to shut it off. Anybody? Thanks, Dan.

Bad95Gts · Post by **Bad95Gts** » Fri Sep 15, 2006 10:14 pm

A better solution may be too have the fuel pump relay rpm activated.
The engine stops and the pump stops.

Mark Workman · Post by **Mark Workman** » Fri Sep 15, 2006 10:43 pm

The last electric pump I used (street car), I ran the power to it thru an oil pressure switch, bypassed when key was in 'start' position. Engine stops...fuel pump shuts off. To simplify the wiring, I mounted it under the dash and teed off the oil pressure gage. It was a Holley item. Here's a link:

http://www.holley.com/data/Products/Tec ... R10367.pdf

SupStk · Post by **SupStk** » Sat Sep 16, 2006 8:31 pm

Another vote for the relay off the oil pressure switch. Do you remember when some of the Mustangs would trigger the inertia switch when closing the back hatch too hard? Just thinking they might be too touchy for a race car environment.

Ed-vancedEngines · Post by **Ed-vancedEngines** » Sun Sep 17, 2006 1:28 am

I am guessing that a launch at a force of approaching or even surpassing 3G's just might trigger the Inertia Switch to shut off right after launch.

Even a force of 1 G could do it maybe.
Most cars now days will pull that 1 G or more.

Ed

wheelsup · Post by **wheelsup** » Tue Sep 19, 2006 8:18 pm

Two thoughts about this:

1 Just because a car flips on it's lid doesn't mean the engine will shut off. A well placed big red master cutoff switch feeding your fuse/switch panel is a good idea that will work as long as your concious.

2 When a fuel cell is upside down, there is no fuel present at the sump to draw from, leaving only the fuel in the line and fuel bowls. That in itself is plenty to cause a nasty fire, and if your windshield is gone, the only thing that will protect you is a helmet, visor and firesuit.

MileHighMan · Post by **MileHighMan** » Tue Sep 19, 2006 10:43 pm

I Thank you for your suggestions everybody!

CFD_Man · Post by **CFD_Man** » Fri Sep 22, 2006 12:27 am

Here is a link to where you can buy a very good one:

http://www.mossmotors.com/Shop/ViewProd ... exID=30823

I have purchased two from them.

I would highly recommend one. With a fuel injected car, nothing says it is going to stop running. I, would in addition, make the fuel pump running dependent on oil pressure.

dwilliams · Post by **dwilliams** » Fri Nov 03, 2006 8:50 am

I'm using a Ford inertia switch. It came from some sort of small truck at the junkyard; it was mounted under the dash. I have a late model Crown Vic main power relay; came off the passenger side fender. It looks like a starter relay.

I'm using a GM fuel injection system on my car. GM has wired the fuel pump relay in various ways over the years. In most setups, the oil pressure switch is only used during the start-up sequence. The engine can lose oil pressure afterward and the computer doesn't care. As long as the pickup can get fuel, the engine will happily run inverted.

I snagged the inertia switch during the conversion because in my advancing age, I can visualize a whole bunch of crash scenarios where I'd be, if not badly hurt, at least knocked stupid by the impact. The side windows on my car (first generation RX7) lean in so sharply that my helmet touches the side of the roof when I sit upright; I've had a few good wallops from that when hitting rough spots on the track.

I asked around some of the places where Ford trackies hang out, and nobody could recall ever having had one of the Ford inertia switches pop at a track event. There's a red reset button on the top. I mounted mine on the transmission hump, where I can reach it while belted in.