Ron Francis sells a crash relay to shut off the electric fuel pump, but like most things they sell it's gold plated, plus I'm a little torqued at them right now anyway but that's a different story.

For less than half price I can go to O'Reilly and get crash relay for a Taurus.

Can I use any old crash relay? Seems like you should be able to.

 

Sure you can, but it depens on what "sets it off"
I have no idea how they are worked/wired.
My first thought is it could be spliced into the airbag system. I don't think so though.

It may have a sensor that measures accel/decelleration. When it see's a real sudden change it sets off.

Of course it could be in the relay somehow. Do a little more research I don't see any reason why you couldn't do it, so long as it's a stand alone system.

 

Don't get too concerned about names...a relay is a relay. The way that this relay works is that the system senses the engine running and activates the relay to allow the pump to function. If the engine stops running then the relay deactivates. Depending on the engine/ignition setup that you are running there will be various methods of detecting that the engine is running, I would think that any tach drive output should work. I would do a little research and see what is available on the market before spending time on designing a circuit from scratch.

I just got to thinking a little more on this subject and I recall using an oil pressure switch to control the relay. Take a look at this link: http://www.how-to-build-hotrods.com/...fuel-pump.html

 

I guess I assumed that is was an impact that triggered the crash relay, I hadn't thought about them being part of the other safety systems but it makes sense.

Hmm, no I'm going to have to figure this out.

 

I believe the unit you're talking about is an inertia switch, not a relay, per se. It is designed to shut off power to the high pressure fuel pump in the event of a collision and triggered by a high force impact. You can get one from a wrecking yard for dirt cheap. Any of them would do the trick.

 

Holley also sells one that is simply an oil pressure activated switch. If the engine loses pressure (which can be in a crash or because a fuel line splits, etc) the pump is shut down.
http://www.holley.com/data/Products/...R9680-1rev.pdf

 

I had a 94 ranger that had an " inertia " switch. It was mounted inside the cab below the heater. It was set off once and there was a reset button on it. Should be cheap in wrecking yards. Just do a Google search for " inertia switch 94 ranger" and you should bring something up.

 

Low oil pressure would be in case of engine problems with the oil and nothing more. The way it works is you must crank the engine to get oil pressure before the fuel pump would turn on if in the fuel pump circuit. If that is your goal then use the oil pressure switch in the ignition circuit.

An inertia switch detects the impact of a crash above a certain level. This opens a circuit that is mechanically held in the closed position (by closed I mean conducting electricity). You have to reset the switch manually to get the pump to run again.

Marty S

 

Lots of fuel injected fords have that relay, and they're readily available in the junk yard.

 

In any decent crash, the engine will die, oil pressure goes to zero, pump shuts off. If you're just driving and a fuel line starts leaking, spraying gas on the engine compartment, the engine will run out of gas and stop, but the pump will still be running unless you have an oil pressure switch. No impact to set off the inertia switch. EFI systems have a similar function built into the computer that generally uses pulses from the ignition system to determine if the engine is running, not oil pressure, to decide whether to keep the pump on.

Two different scenarios, you have to decide whether you only want to shut off the pump because of a major accident, or because any of several other problems have occured. Maybe you need both? The gov't thinks so.

 

Wavetrain; I'm not sure what system you are using from Ron F. But the one I used for a 96 4.6 DOHC from a Mark VIII calls for an inertia switch so I went to the junk yard and took one from the trunk area (D/S fender)of a Lincoln and it works just fine. The system I have doesn't use the low oil pressure switch.
I'm not to pleased with their flash of the ECU, had them do it twice now and it still throws codes for the EGR which was eliminated.
Good luck in your quest!

 

I hate to be the nay-sayer, but I gotta ask and throw my 2 cents in....
I have had (ignoring the ancient pre inertia switch models):
tempo, tracer, pontiac g6
My mom has had:
taurus, sable, contour, pontiac g6
my sister has had:
tracer, honda pilot
my other sister has had:
pontiac sunbird
my girlfriend has had:
subaru legacy, honda civic

Every single one of the american made has had the inertia switch start acting funny - doing stupid SH** like tripping for no reason at all. Almost always it has been after parking the car, but twice it has been while going down the road. Generally starting around 80k miles.

The two g6's haven't hit 80k yet but I expect problems of them eventually.

One time the contour (last weekend in fact) left my mother stranded 3 hours away from me. As I was preparing for a 6 hour rescue trip I walked her through every diagnostic I could think of and barely managed to save my butt the drive.

I'll give you a huge piece of advice. Do NOT scavenge an inertia switch from an american made car of any sort. Now that said, the american and chinese / korean made cars share parts in china. The Jap cars so far have had zero hiccup and I suspect their inertia switches are Jap made (dunno, never had a problem, never looked at them).

I'm going to emphasize this. There is absolutely no good reason (in my opinion) to add one of these. If you get in a wreck in these old classics with no crumple zones one of two things is going to happen. 1) you'll stay concious (minor accident) and turn the key off yourself 2) you'll die (medium+ accident) - then who cares let the firefighters sort it out. There's not much middle ground for survivability here. I know this is a bit sharp and will almost certainly get some "feedback" but ignoring the emotional response these bloody inertia switches have caused absolutely nothing but headache (and a lot of it) and I have never seen any proof that they are a good idea, it seems to me they are just a politically mandated "sounds like a good idea".

Now if you want to spend money improving the safety in your vehicle I would really strongly suggest things like airbags for the before mentioned crash #2 scenerio.

It's your money and time do as you wish, but I'll just warn you - be prepared to "fiddle" with yet another system as it constantly gives you headaches in the future.

 

I tend to agree with you there.

 

Boy, Brian, you must have the worst luck. I have never owned anything but an American car since 1962 and have never had a problem with one. Plus I am part of a Christian ministry that repairs cars for single parents, those on a fixed income and other deserving people for the last 20 years and have never seen this kind of failure.

I plan on using an electric fuel pump on my '52 and I damn sure want some sort of device to shut the fuel off in the event of an accident that renders me unconscious such as a T-Bone where I'm the T.

 

Oh ford trucks have by far been the most reliable things I've ever driven. Unfortunately those were all hard worked trucks on the farm - not anything I owned, just drove. You'd, think I was some 60 year old codger all bent outta shape from my earlier post I know, but I'm not even 40 yet... and a dodge truck I drove for work was the WORST vehicle I've ever diven... but I wont digress on that too deeply.

Here's a comparative... my girlfriend flipped her subaru legacy upside down one snowy day (single vehicle accident - hit black ice and lost it). when it came to a rest, the pump was pumpin out fuel and tank was leaking out the top (into the passenger cabin)... so I wouldn't spend "like gold" dollars on something that in my experience has had 90% false positive failure rates and 25% false negative rates - the bloody things just don't work.