Featured Technical Cheap $5 junkyard part could save your life.

If you are running an electric fuel pump on any of your vehicles, it is critically important that you have an inline inertia switch that will cut the power to the fuel pump if you are in a wreck. Ford uses a simple, easy to wire inertia switch that you can grab off any Ford vehicle made in the last 30 years that has an electric fuel pump. This one came off a '99 Mercury Grand Marquis. This switch is easiest to get to on Crown Vics, Grand Marquis, and Lincoln Town Cars, inside the trunk on the left quarter panel. One screw that takes an 8 mm wrench, and cut off the plug from the wiring harness and a couple of inches of wire to make it easy to wire into the electric fuel pump circuit. It has a red reset button on top. Once with a '90 Ranger many years ago, I hit a patch of ice and slid into a curb, no damage, but it activated the safety switch and cut the power to the fuel pump. All I had to do was press the red button to reset.

 

Would a hard launch or coming down from a wheelie trip it?

 

They’re in the right kick panels on the pickups. I would pop it with a screw driver while running to depressurization the fuel system when I changed the fuel filters on my pickups.

 

That is a smart idea, easy to hide away and can be used as a anti theft device. thanks

 

Don't know if coming down from a wheelie would trip it or not. The car I took it off of was wrecked in the front with airbags deployed, and the fuel pump inertia switch was tripped by the accident. Just had to press the reset button. Don't think it would work as an anti-theft device, as it takes an impact to trigger it. But you could put a hidden toggle switch in the power feed to the fuel pump as an anti-theft device.

 

You could also wire a pump to only run when there is oil pressure or the starter is in use. Not fool proof (nothing is), but it's a good step up from having the pump active all the time the ignition is on.

 

^^I have a hidden switch in the pump feed...it works.
Inertia switch is a good idea. I've always run the pump feed through a normally open, 10 lb. pressure switch plumbed into an engine oil port. Doubles as an engine shut down in case of lose of oil pressure when the engine is running also. An inertia switch wired up in series with the the press. switch would be an added safety feature.

 

Ford cutoff inertia switches are in the trunk of all EFI cars. The Foxbody Mustang switch is very small. Also a 2 wire setup.

 

I mounted an inertia switch in my rod, but was hoping I wouldn't get inadvertently trips in normal driving. A few thousand miles later, no trips.

I run a mechanical fuel pump, and use the electric pump with a toggle switch to prime the carb, as the fuel bowl evaporates in a week or so.

The problem with the oil pressure switch connecting the electric pump is you loose the ability to prime the carb.

 

Looks like a trip to Pull a Part!!

 

With a mechanical fuel pump you could make the inertia switch kill the ignition so that in the event of an accident the ignition would shut down stopping the engine and thus the mechanical fuel pump.

 

Similar thing found on propane powered forklifts, but relies on an ignition pulse to operate.

 

Back many moons ago, I worked at Lincoln Mercury store in an area of lots of golf courses. I can't tell you, aĺ the times that Lincolns and big Mercs were towed in for a no start condition because the owner or passenger threw a loaded golf bag into the trunk and banged the flybrace, tripping the switch. Of course the car. Was towed it under warranty for a no start condition. The owners weren't happy about paying for a tow and servicer department charges because Ford didn't cover banging a golf bag into the rollover switch while loading their clubs! We rarely ever had one tripped otherwise unless it was a real traffic collision. Lots of unhappy golfers though.

 

Are you pulling fuel through the electric pump with the mechanical pump?

 

Perhaps. There have been plenty of people with Ford trucks and SUVs who've tripped them doing off road stuff.

If some cargo (I can attest that a couple HP electric motor is sufficient) falls off the passenger seat under braking or the passenger stomps on the floor of your Ford Ranger, Explorer or Aerostar (the switch is mounted where the firewall, tunnel and floor meet just above the passenger's left toe in those) it will fairly reliably kill the fuel.

And as deucmac said, the ones with trunk mounted ones are pretty susceptible to cargo being tossed around.

99.9% of the benefit of a cutoff switch can be had by wiring the fuel pump relay to run with either oil pressure or starter. If you're driving your car so infrequently as to need to prime the carb a simple momentary switch can be added.

If anyone is dead set on using an inertia switch the right side kick panel mount on 80s Ford trucks and vans seems to be the best mounting configuration to prevent being inadvertently tripped.

 

Hard launch, no. Soft wheelie landing, no. Hard wheelie landing, yes.

I've owned several Fords with the same switch, never tripped one, and I've done hard launches, soft wheelies, and off roading.

For a stock replacement version, an easy way to remember what to get is just grab one for a 2000 Ford, any model. They're less than $40 and you can get a pigtail for them as well. You can put this wherever you like for ease of access and it just wires inline for the power wire to your fuel pump. You can also wire this into ignition module or coil wire power. Hopefully you'll never need it.

 

Yes. I have the Carter GP4070 mounted on the frame rail near the tank.
I use it to prime the carb. Also, if I get a vapor lock, I click it on and continue down the road.
Normal driving is on the GM mechanical pump.

 

I have an '06 Grand Marquis daily driver, have had two Mercury Sables ('92 and '97), an '00 Focus, and a '90 Ranger, all with the same inertia switch. Only time I ever tripped the inertia switch on any of them was when I hit a patch of ice in the Ranger and slid to a stop against a curb. Never tripped it throwing stuff in the trunk.

 

Or a lady in a Taurus wagon going over a speed bump in the mall parking lot.

 

What's the labor charge at a dealership to mash the little red reset button? (I'm in Georgia--we don't "press" buttons, we mash them.)

 

Excellent idea! Good info! Thanks!





Bones

 

Great idea and an easily procured solution. Thanks!

 

I never tripped the one in my ‘87 Escort terrace jumping but I did once trip it bumping over the curb into my drive way.

 

Years ago our 1986 Taurus would trip periodically for no reason. Have seen the same scenario on other Ford products. May be wiser to go with a new switch to avoid this eventuality.

 

This kinda seems like a solution looking for a problem to me, but I don’t run electric pumps on anything.

 

With an electric fuel pump, there is a fire risk if you're in an accident, the engine stops, and the fuel pump is still running. If you have a fire, you don't want the fuel pump feeding it gasoline.

 

Oh I understand what they are and why ford uses them. I just don’t know that it’s a big concern for our cars

 

The inertia switch is only present on EFI models. Ford EEC-IV and later primes the pump at initial key on and then doesn't run it again until it sees a signal from the distributor or crank sensor. Any crash that breaches the fuel system will stop the engine which itself will stop the fuel system because once the engine is no longer getting fuel it will stop running and then the pump will stop too. The switch mostly just turns minor accidents into problems that require a tow truck. There's a reason other OEMs don't use them.

 

efi systems run significantly higher pressures than what it takes to feed a couple of strombergs.
certainly not needed in all electric fuel pump applications.
keep it simple

 

I use these switches in anything with an electric pump. They work well and are cheap and reliable.

they are designed to trip when hit horizontally, not when you go over a bump. The switch needs to be mounted with the button on top.

my dad mounted one on its side and it would trip on speed bumps. Turning it 90° so the button pointed up fixed that problem.