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I noticed someone mentioned a fuel injector kill switch mod and wondered who had done it and how it was used?

I don't mind keying the car off and then back to AC position with a 2 second delay (to avoid dieseling) but I can't do it when it's dark because my car kills the headlights on key off. They also cut out during start up -- I'm not sure if that is by design or due to current draw.

Does anyone have any ideas around improving this behavior?

Hi Sean:

___The way I believe Randall setup his Insight and Larry his Saturn was to ground the injector wires w/ a latching relay on FAS-switch initiation which caused an instant Fuel cut and no key needed ;) Hopefully they will respond to your plea for information shortly.

___Good Luck

___Wayne

Thanks for the info, Wayne! Do you happen to know how they light the engine again? It sounds like a simple mod with low equipment cost.

Hi Right Lane Cruiser:

___In the case of Randall’s Insight, they are already wired to spin up the ICE when shifted back into gear via IMA so that one is automatic. With Larry’s Saturn, I believe he has to take the key from IG-II to IG-III and let it spring back to IG-II just like normal once the Fuel cut relays are evoked but bypasses IG-I (off) altogether. I have no idea how your Elantra is wired for the final key forward to reignite the ICE as well as letting the injectors loose to re-supply fuel.

___I think you should wait for Larry to join this conversation as I am speaking for him and may be passing on incorrect information. With enough relays, you can make your car do anything but its reliability begins to wane the more HW you add. Injectors are possibly the most important item in your ICE and you wouldn’t want your mod to take you out in the middle of nowhere at 02:00 AM for example …

___Good Luck

___Wayne

Sean, Wayne is correct, I used a relay to cut the power to the injectors. I'm not sure how your car is wired but I suspect that most cars are wired the same. Here's how I did mine:
There are 2 wires going to each injector. One is the power wire and the other is the ground. The cars computer(ECU) switches the ground to determine pulse width/rate.

I got a 5-terminal relay and cut all of the power wires going to the injectors. On my car they were all the same color-pink. Then, strip the insulation off the wires coming from the wiring harness and tie them all together.

Then, strip the insulation on the wires that are still connected to the injectors and tie them together.

Next, take the bundle of wires from the injectors and connect them to the terminals on the relay that are normally closed(on).

Next, take the bundle of wires from the harness(hot) and connect it to the input terminal of the relay.

Next, take the wire that supplies juice to the relay and connect it to the hot(harness side) of the power wires.

Next, connect a wire to the ground side of the power relay and run that into the cabin to a switch.

Find a suitable ground and coonect a wire from there to the other side of the switch.

What happens when you flip the switch is, the relay switches the wires going to the injectors to the set of contacts that aren't being used so the injector won't operate. When you flip the switch back, the relay loses power and it switches back to the normally closed set of contacts and the injectors are again ready to operate when the engine is re-started. On my car, I just put the car in gear and quickly let the clutch out just enough to light the ICE then back in untill the rpm's stabilize then continue with the next pulse. Occasionally, I have to turn the key from run to accessory then back to run before the ICE will start. According to the owner's manual it's supposed to do this all the time for safety purposes but the majority of the time it doesn't. The nice thing is that on my Saturn, the accessory posistion is the next position down from run and the power to the radio, electonics, etc. is never interupted and I don't have to worry about accidentally locking the steering column; not good.:eek: This also means that there is no distance lost on the odometer while the key is off and you're waiting for the engine to completely stop. I hope this helps. If there are any questions I'd be glad to do my best to answer them.
By the way, if you are using the key to re-start, most cars will disengage all accesories to provide as much current as possible to the starter.

Wayne -- thanks for the warning. I like reliability!!

diamondlarry -- That was quite detailed -- thank you!

Sounds like you manually flip the switch back and forth? Have you ever thought of wiring into the ignition switch with a latching flip-flop so that alternating flips from run to start either engage the starter motor or cut out the fuel injectors?

I think my car probably behaves the way yours does based on my experience with killing the engine with not enough throttle. :embarassed: I don't have to switch back one position to get it to start.

If I implemented this I'm sure the headlights wouldn't go off when I cut the fuel injectors out, but do you have any ideas about preventing them from going out when I start again? The turn signals don't quit and the parking lights don't go out... though they do dim a bit. I can live with dimming but don't like being mistaken for one of those guys who flashes people when they don't get going fast enough.

Wayne -- thanks for the warning. I like reliability!!

diamondlarry -- That was quite detailed -- thank you!

Sounds like you manually flip the switch back and forth? Have you ever thought of wiring into the ignition switch with a latching flip-flop so that alternating flips from run to start either engage the starter motor or cut out the fuel injectors?

I think my car probably behaves the way yours does based on my experience with killing the engine with not enough throttle. :embarassed: I don't have to switch back one position to get it to start.

If I implemented this I'm sure the headlights wouldn't go off when I cut the fuel injectors out, but do you have any ideas about preventing them from going out when I start again? The turn signals don't quit and the parking lights don't go out... though they do dim a bit. I can live with dimming but don't like being mistaken for one of those guys who flashes people when they don't get going fast enough.

I forgot to mention that I actually have two switches. One, which I use most of the time, is a momentary/spring loaded push switch. I also have a toggle switch which I could use for going down long, steep grades. The reason for doing it the way I do is to cut down on the amount of time that the key is off and the odometer not counting mileage.

I think the only way to keep them from going out would be to bump start by popping the clutch while you're rolling.

diamondlarry -- Do you just hold in the pushbutton for a couple of second?

Maybe I should learn how to bump start, huh? I've been driving a stick for 9 years now and still have never tried it... I presume that the wear due to this procedure would be rather severe unless performed at very low speeds?

Sorry for asking so many questions -- this place is like a candy store to a small child!

diamondlarry -- Do you just hold in the pushbutton for a couple of second?

Maybe I should learn how to bump start, huh? I've been driving a stick for 9 years now and still have never tried it... I presume that the wear due to this procedure would be rather severe unless performed at very low speeds?

Sorry for asking so many questions -- this place is like a candy store to a small child!

I've only started bump starting in the last week and it's a piece of cake. Best results are using the gear higher than you would drive at the speed your going for a very smooth start. This kicks you over at around 1000rpm. If clutch wear is a concern, my impression is it's no more harsh than downshifting, less so possibly.

Try it a couple times and you'll be hooked.

worthywads -- Last week?? What's the highest speed you've done this? Do you just drop the clutch and give it some gas or do you need to double clutch it?

Does this method use less fuel to restart (do you know)?

worthywads -- Last week?? What's the highest speed you've done this? Do you just drop the clutch and give it some gas or do you need to double clutch it?

Does this method use less fuel to restart (do you know)?

Don't know for sure on which uses less fuel. Either method seems to produce some unexpected open loop mode immediately after start up while gently accelerating though?

The highest speed I've done it is 45-50 in 5th gear, but I'd use 5th at 35 too, which is where I would normally shift into 4th.

Higher speeds haven't come up, I suppose at 75 I'd start with starter then tach up.

I'm a newbie just like you, but I'm predicting you'll be fasing and bump starting like a pro by the end of the week.

worthywads -- Last week?? What's the highest speed you've done this? Do you just drop the clutch and give it some gas or do you need to double clutch it?

Does this method use less fuel to restart (do you know)?

I think that doing the double-clutch method would give the smoothest restart. I've already done it so smoothly that one of my passengers never knew that I was doing it. As for top speed, I've bump-started as high as 60-65 mph. The smoother you can get, the less wear on the drivetrain and the battery too for that matter.

Well, I tried it out on the way to work this morning... I didn't try the double clutch and the car felt like it hit a good sized pothole. :rolleyes: I'll definitely be trying to smooth that out!!

diamondlarry -- if a passenger couldn't tell that is MIGHTY smooth! Hopefully I can get to that level myself. I shoot for maximum smoothness in all my driving figuring that will mean less wear and less wasted energy. By the way, you were right about the lights staying on during bump start (I guess there isn't a reason for them to cut out in that mode anyway...) so if I can smooth it out I'm down to one headlight blink in the dark.

Since all the (+) sides of the injectors are tied together, there
is probably ONE wire that needs to be interrupted rather than
all four. The wire in question may even conveniently pass through
the inside of the cabin somewhere, such as where the ECM is,
allowing easier and cleaner access than messing around with
the injector harness.
.
Also keep in mind that if an injector happens to be open just
when the relay opens, it's going to generate a bit of a voltage
spike across the contacts. A small capacitor across the relay
contacts may help mitigate that.
.
_H*

Here's the link to the Insight F_A_S mod.
Looks like Larry may have you going on your vehicle.
Might get some ideas though.

http://www.cleanmpg.com/forums/showthread.php?t=2563

Randall

highwater -- Wow. That's quite a mod! How long did it take you to figure out all that stuff??

Since all the (+) sides of the injectors are tied together, there
is probably ONE wire that needs to be interrupted rather than
all four. The wire in question may even conveniently pass through
the inside of the cabin somewhere, such as where the ECM is,
allowing easier and cleaner access than messing around with
the injector harness.
.
Also keep in mind that if an injector happens to be open just
when the relay opens, it's going to generate a bit of a voltage
spike across the contacts. A small capacitor across the relay
contacts may help mitigate that.
.
_H*

That's what we thought when we installed this on my first Saturn. But, when we started tracing the wires back throught the harness, we realized that Saturn, in their infinite wisdom:rolleyes: , ran a separate wire for each injector. When you figure how many cars they did this on you can't help but wonder how much cash they could have saved by running one wire and branching off for each injector.

So that's *eight* wires coming out of the ECU? Four
positives and four [switched] negatives? Very weird. Bet
that if you ohmed out all the positives you'd simply find
them all tied together. Unless they're trying to H-bridge
each injector in some fancy way to get it close faster..
.
_H*

To answer the above question... most likely, the PCM does not supply the power to the injectors... the PCM only does the switching to ground, so you'd find only the 4 ground wires going back to the PCM. The 4 power wires likely can be traced back to a single point (a relay, junction box, fuse panel...). Sometimes there are splices made inside the harness itself.

Question to you Hobbit... I had the same concern about the inductance of the injector causing a spike when you suddenly open the circuit with the FAS switch, with nowhere for that energy to dissipate. Your previous post suggested a capacitor wired across the relay. I like this idea. This would give a current path when the relay is opened, until the capacitor is charged, and then it would behave like an open circuit... no sudden change in current. However, what will happen when the relay is closed again (after releasing the FAS switch)? That capacitor across the relay is charged up, and when closing the relay, wouldn't we be essentially shorting out that capacitor, causing a sudden discharge into the low resistance relay? It seems that the circuit would also need a small resistor to prevent this sudden discharge. I don't want to introduce a "time constant" into the system though (RC circuit), which would change the timing of the PWM pulse going to the injector during normal operation. If we put this added resistor in series with the capacitor across the relay, then there should be no current through this leg of the circuit during normal engine operation, right? So that would mean we would not be changing the time constant of the system, right?

Has anyone experienced damage to either your injectors or PCM after using a FAS switch (without this sort of circuit protection)? Anybody happen to know if the injector itself typically has a protection diode or something inside?

Either method seems to produce some unexpected open loop mode immediately after start up while gently accelerating though?

I noticed this as well and I believe that it is normal operation. The CPU thinks it needs to warm up the cat converter all over again.

I have gotten to the point where a friend of mine was riding with me, and while he knew that I had shut off the engine, he couldn't tell how I had restarted it. He had to ask since he had been watching to see when I would reach for the key. The restart was at 18 mph in 5th gear.