Fuel shutoff

dmcdlrn · 03-19-2006, 11:02 PM

Ok, this may have been discussed before or even done, but I couldn't find it. I was thinking the other day that it would be really awesome if instead of stevieg's access control I made something that demanded a password "ignition code" and if it didn't get it within 30 seconds it would kill the fuel pump or injector electrical circuit or something necessary but not crippling to the handling of the vehicle so that they wouldn't crash... just not be able to get away. You could have it either ask for it imediately or delay 10 seconds or something.. but then progressively get more emphatic and warn of vehicle disabling at the expiry time.

It would require a simple application that I could code with a few helps from people on board here that have better coding skill than I (or would want to do it for me

) , a usb i/o interface... phidget or vellman ect. with atleast 2 digital outs, and a latching relay. The application would send a pulse to the relay which would effectively switch the power off to the pump... it will remain off until thrown back... this would keep crafty theves (whom at this point probably are running cause they are still too close to the crime scene and won't want to pop the hood for a better look) from shutting the car off... wating for the pc to go off then starting it again and making it farther... or ripping the pc out so that it won't hold the relay open. The other "optional" but really recommended item would be a bypass... we love our computers, but lets face it... they are untrustworthy at best. I would go with either a hidden switch or, my preference... a key switch in the glove box... you would have to open the glove box and insert a key ( which I would keep in my wallet or locked in the trunk or something seperate from the key ring) to get it to run again.

The software could be really indepth or simple... but you could add like service mode which would allow a simple code to access it for limited time, or just limited time with countdown on screen letting them know that they better not try any crap. A limited number of tries... logging... different passwords for family members (lol, not usefull for me

) shutdown after a period of time after code failure... so that if they run the battery doesn't crap out with the key on...

I'm sure there are bugs, but it seems like a great idea, and given my poor creativity skills... I figure somebody must have atleast thought of this... but I couldn't find anything in searches... there has to be some obvious problem I'm overlooking

dmcdlrn · 03-19-2006, 11:03 PM

by the way... this isn't replacing the key or starting... the car would start and run like normal and only stop if you didn't put the code in.

walky_talky20 · 03-19-2006, 11:27 PM

It seems like a simple hidden switch or key-switch would do the trick without the complications associated with hooking it to the computer. Although you would lose that "The Transporter" effect

It also seems like the 30 second delay-before-cutoff could be potentially dangerous. Cutting the fuel pump while the car is in motion is probably not a good idea. What if it quit in the middle of an intersection or something? It would probably be safer if this killing the fuel pump business stayed in the parking lot.

Good Luck.

dmcdlrn · 03-19-2006, 11:53 PM

if it does... they can't say they weren't warned... and you plan on disabling and reenabling the fuel pump everytime you get in... thats basically like turning the key... this would do it only if it detects un authorized entry.. I put a code in every time I get in my car anyways... so now it just would shut off the fuel pump.

TheLlama · 03-20-2006, 12:16 AM

I wouldn't trust software to control my fuel pump. There is a big difference between the embedded industrial computer that controls your car where all the software has undergone tremendous testing to something hooked up through the parallel port to a computer running Windows. I would be weary of doing this even if I wrote the code myself.

adaminc · 03-20-2006, 12:33 AM

I'd use a microcontroller to do it

Chris31 · 03-20-2006, 02:14 AM

Use one of those electronic "combination lock" kit.

kiltjim · 03-20-2006, 07:47 AM

Quote: Originally Posted by adaminc

I'd use a microcontroller to do it

This seems like the best alternative. You can have it display the keypad, or run off of one, and they are going to be much more reliable if you know what you are doing, and they also have a nearly instant boot time.

dmcdlrn · 03-20-2006, 08:29 AM

ok, so basically people just don't trust their computers. Worst case the thing would screw up and shut off the fuel pump while driving. The car would coast to a stop and the bypass would be initiated and I would be on my way again.

Any other reasons then just not trusting their computers?

walky_talky20 · 03-20-2006, 10:29 AM

I don't think coasting to stop is really the worst case. If you lose the fuel pump you also lose a lot of other stuff. Power Steering and Power Brakes to start with. And imagine the fuel pump cutting out while making a left turn into McDonalds (across traffic). The car stalls in the path of oncoming traffic. The point is, it could potentially be a lot more dangerous than "The car would coast to a stop".

greenman100 · 03-20-2006, 10:38 AM

Quote: Originally Posted by walky_talky20

I don't think coasting to stop is really the worst case. If you lose the fuel pump you also lose a lot of other stuff. Power Steering and Power Brakes to start with. And imagine the fuel pump cutting out while making a left turn into McDonalds (across traffic). The car stalls in the path of oncoming traffic. The point is, it could potentially be a lot more dangerous than "The car would coast to a stop".

Actually, it would.

Have you ever turned your key off at 65 MPH?

Same effect as closing the throttle plate. If fact, on my Explorer, the fuel injectors are shut off when the throttle is closed and engine RPM > idle

dmcdlrn · 03-20-2006, 10:39 AM

Well first off.. power brakes and power steering are minimal... I have drivin several cars in my life without steering, and brakes I have had completely fail on me before at an intersection and I still stopped... I have a light weight manual with a good ebrake. In order to get this to fail the computer would have to somehow throw a pulse with the application shut down and the card uninitialized to the proper output. Thats about as likely as your cd tray ejecting on its own... the computer would have to inadvertently send a pulse to the release latch.

dmcdlrn · 03-20-2006, 10:41 AM

Quote: Originally Posted by greenman100

Actually, it would.

Have you ever turned your key off at 65 MPH?

Same effect as closing the throttle plate. If fact, on my Explorer, the fuel injectors are shut off when the throttle is closed and engine RPM > idle

what about speed limiter... ever hit that... my z did that at 138... alittle violent, but if your not a crappy driver your passengers wouldn't even say anything more then... what was that?

haha, except... what the heck are we doing 138 for!!!! then they soil themselves.

I'm not just trying to argue or be an idiot... I'm just trying to gather some valid reasons why not to do this. To this point I'm not super convinced with well there is the remote chance that it could somehow shut the fuel off while your driving it... and thats unsafe... common guys... we all have touch screens in our dash... really, is that safe?!

Oh, and I'm not sure exactly what your saying green... it could go either way... sounds like your saying it would be bad, but then your saying that your truck does it stock... I'm sure I'm just not reading it well.

kiltjim · 03-20-2006, 11:42 PM

Quote: Originally Posted by greenman100

Have you ever turned your key off at 65 MPH?

Actually, I think the result would differ from car to car. I had a '92 Pontiac Grand Am, and for whatever reason, the car would act really weird everyonce and a while. I would have to shift to nuetral, and restart the car. It was an electrical problem, but the car wouldn't stall, so I would have to shut off the car first, before restarting.

I tried the same thing in a Kia, just to see what would happen, and it made a loud bad noise. I was young, and it wasn't my car, so I wasn't concerned about what the loud noise was (wasn't the starter if that's what you are thinking).

But it is your car. All these projects are completely custom, so if it works in your car, go for it. I really think that you should use a dedicated controller though. I'm not worried about the effects on the car, just the repetitive problems you might have. Its fine if it happens once, and nothing happens. It is going to be a pain in the *** if it happens all the time because you run low on ram, and the computer crashes.

dmcdlrn · 03-20-2006, 11:50 PM

Well thats the thing... the application would be triggered by hibernation... when it reboots from hibernation the application comes up... if you don't put in the password then the application stays and ultimately shuts off the fuel... if you put in the password... the application exits completely. There is no ram issues... no crashing... it would have to initialize the card and send the code to it to send 12 volts to the relay in order to open it... remember that its a latching relay... so it would stay closed unless told to open... then it would stay open until told to close...

If it happened once I would take it out... but I don't expect it to ever happen let alone repeatedly.