Fuel Pump cut off

[trikkonceptz]

I know this may sound lazy and overkill for some, but is there a way to wire up your fuel pump to shut off when your car hits 0mph?

Yes it's easier to just turn off your key, but for that instant for example @ night, you would shut off your headlights/tail lights and such and could get in trouble for doing so. This way, when you come to a stop, your car shuts off in like 10 seconds and all you have to do is turn your key to the start position or hit your auto start button, to get the car back on without really interrupting power.

Or is there a quicker way to kill your engine other than turing the key?

This would also help newbies to remember to shut off their cars, like me .. LOL

[diesel_john]

I have switch in the wire that supplies 12v to the fuel injectors and it works great. ON most cars all the fuel injectors are supplied 12v by one wire and then the ECU grounds the other injector wires individually to open them.



edited to spell out that the ECU grounds the other injector wire, not the 12v one.

[LostCause]

I know of three different ways that people have created kill switches: ignition cut-off, fuel pump cut-off, and injector cut-off.

Ignition cut-off is less then ideal because the injectors fire before the engine finally stops. In a sport that seeks to save fuel, running even a cycle longer then needed seems wasteful.

Fuel pump cut-off is definately doable. I believe it has been done by members on this site, but there is usually a delay from when the fuel pump is cut and when the engine finally stops.

Injector cut-off is the most graceful solution in my mind as it instantly stops the engine without wasting fuel. Hopefully someone with some expertise can suggest how a cut-off could be built.

I'd consider performing a search on this forum as I believe the question has come up before. It's been awhile, though.

- LostCause

[trikkonceptz]

Originally Posted by diesel_john

I have switch in the wire that supplies 12v to the fuel injectors and it works great. See, on most cars all the fuel injectors are supplied 12v by one wire and then the ECU grounds them individually to open them.

That sounds like the most efficient way to shut off the engine, pardon the pun ...

Now is there anyway for this to happen automatically when the vehicle hits 0mph, isn't this what the hybrids do?

Does the scangauge read speed? If it does there has to be a way.

[Joe_Bloe]

Originally Posted by diesel_john

I have switch in the wire that supplies 12v to the fuel injectors and it works great. See, on most cars all the fuel injectors are supplied 12v by one wire and then the ECU grounds them individually to open them.

John, do you have any pictures or a write-up of this mod? I am really getting into Engine-off Coast in my PT Cruiser, I've taken my mostly-city-driving MPG from about 26 to almost 30. But I don't like turning the key -- I want a kill button that doesn't kill the ignition. Killing the fuel injectors would be perfect.

[Daox]

Originally Posted by trikkonceptz

That sounds like the most efficient way to shut off the engine, pardon the pun ...

Now is there anyway for this to happen automatically when the vehicle hits 0mph, isn't this what the hybrids do?

Does the scangauge read speed? If it does there has to be a way.

This is more complicated than it seems. You would need to build a circuit with some built in logic otherwise you'd never be able to start your car again (speed @ 0 = no fuel, startup = 0 mph).

Its much easier and more efficient to manually kill the engine. Sensors can't see the yellow/red light up ahead, you can.

An engine kill switch is fairly easy to impliment. The best way (IMO) is to use wire a the switch to control normally closed relays that are in line with the injector signal wires. This way, if anything fails your car will still run. DiamondLarry had this done on one of his Saturns. I think he even did a write up somewhere. Hopefully he'll chime in.

[JohnnyGrey]

I have switch in the wire that supplies 12v to the fuel injectors and it works great. See, on most cars all the fuel injectors are supplied 12v by one wire and then the ECU grounds them individually to open them.

So then your ECU is trying to ground 12v? That can't be good.

One option you can consider is realigning your idle air control valve, then unplugging it. Then your engine will die unless you feather the throttle. It's easy to do for most cars.

1. Pull your brake booster hose and put your thumb over 90% of it.
2. Once your IAC closes, while trying to bring down the elevated idle, unplug it.
3. Put the booster hose back on and your engine will die.

[tasdrouille]

My Hyundai has an inj fuse, so it's really easy to kill the injectors. IIRC some saturns have that too, probably others also.

[trikkonceptz]

For those with 12v supply to the injectors, how about a momentary switch that once you press (and hold) would kill the power, once you release it, you should be able to restart the car no problems.

I'm going for a certain cool factor here, 1 touch shuts off car, push button restarts it. Yeah sounds silly, but if I'm gonna do it, I might as well enjoy it ...

[Who]

If the switch were a toggle rather than a push button it might also serve as a theft deterrent.