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Discussion Starter · #1 ·
I'm thinking about installing a kill switch and interrupting the crank position signal as the way to do it. Just wondering what pin/wire of the comp/harness is the crank position sensor's on an 07 2.0 duratec? I'll run a relay in line for the sensor and control it's ground through the kill switch. Also, other than throwing a code, are there other problems that this could create? Like, does the sensor need to be recalibrated or anything when the switch is used? Or does everything go back to normal once the wire is "reconnected"?
 

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C2H5OH
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You mean that needing a coded key isn't safe enough?


I don't know what you think you're going to accomplish, but it won't be much other than another headache for us when your shit breaks and you ask us for help to fix it.
Leave wellenough alone and just drive it.
 

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Discussion Starter · #3 ·
My shit doesn't break very often and I know well enough to fix it on my own most times. I join forums because I know how to search and look for characteristic problems and address them before they arise. Luckily these cars seem to mostly have non-critical problems like hatch wiring which I already fixed and trunk buttons that I don't care about. I want to know the wire and possible issue so I can shut the engine down on long coasts and at red lights to save gas. Using a momentary switch to control the relay for the sensor should kill the engine quickly without me having to cycle the key a million times. Let's not get into whether or not what I am doing is dangerous or worth it, I'm doing it already using my key, I'm trying to not wear out the ignition and accomplish the same thing.
 

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C2H5OH
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Hmmm,
but how will you restart the car?

Do you see where you'll save no ware on the cylinder? You're still going to be turning it.


And I'm not concerned with your safety in the least. It's those you share the road with that I am. Perhaps you may want to think of them just a bit. Please.
 

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OK, I so answered before you posted the reasons for wanting to do this. The only remark I will make is that you must never switch off engine when the car is moving. I'm assuming that coasting is the same as cruising, the term we use over here.

CKP re-sync is done automatically with a notch on the crank pulley or the flywheel, depending where the CKP is mounted.

I also believe you have a 3-wire CKP, the digital variant. In this case, the outer pins are the V-Ref and V-Gnd while the middle pin is the V-Out. All wires terminate on the PCM but the actual pin-outs may vary, depending on the engine code and the PCM version. But you should be able to trace them with a continuity tester.

Good Luck.
 

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Discussion Starter · #7 ·
Thanks polygon, so what you are saying is that once the wire of choice is "reconnected" everything will function like normal? I would normally not be concerned but in searching for crank sensor stuff on here I found the how-to on replacing the sensor and since it's the most complicated sensor replacement I've ever seen, thought I should make sure there wouldn't be a problem with essentially creating a broken wire in the system many times per drive. I'll probably break the ground wire, snow coming so I won't be doing anything too soon but wanted to get my ducks in row ahead of time.

In reference to the inertia switch: the engine won't die immediately when the fuel pump is stopped and can make for long crank restarts if the pump doesn't build up enough pressure on the reprime. I don't like to be a nuisance on the road while hyperming so I need things to get back to normal quickly so I don't get shot while not racing away immediately after the light turns green...
 

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...so what you are saying is that once the wire of choice is "reconnected" everything will function like normal?
Although shutting off an engine in that manner is uncharted territory for me, I'm certain that the engine will find its reference position once the CKP is reconnected and you start cranking. There is no default crank position when an engine stops and it's no different from turning the crank pulley by hand and then start - the CKP uses the notch or missing tooth to handshake the reference point with the PCM.

As far as I can determine, the only drawback with your method is that you're going to drive the PCM crazy. Test extensively and keep the additional wiring and relay contacts to minimum resistance as you're dealing with low and fast changing voltages (9-12V) if you plan to use the V-Out. Like you said, the Gnd seems to be a better choice.

You might also find helpful the detailed wiring schematics that I uploaded here -

http://s000.tinyupload.com/?file_id=49933290919440442592
http://s000.tinyupload.com/?file_id=54866455401029449204
http://s000.tinyupload.com/?file_id=44404984803623753334

They basically cover everything electrical for a wide range of Focus engines and I hope that your specific model is somewhere in there.

And you are absolutely right about the inertia switch and the only reason I mentioned it was because I thought you're doing this for additional security. Anyways, good luck with your project and let us know how it goes once it's set up.

Cheers
 

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Crank sensor wiring doesn't seem like a wonderful way to shut it down, how about power to the PCM as used to turn it on & off with the key?
 

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Discussion Starter · #10 ·
Thanks polygon, I'll have to download them when I get off work and can get on my computer.

Sailer: I'm open to all options but will interrupting PCM power cause my dome light to come on and headlamps go off? Trying to maintain good visibility while driving (another issue with using the key). The usual way to do this on an older car is to replace the injector fuse with spades, inline fuse and your switch. Thus stalling the engine when the injectors lose power. But we don't have that on the Focus as far as I can tell from the owners manual so I'm looking into other options and one person on a different site said that interrupting the crank sensor has been working perfectly on his Subaru so I thought I'd explore that avenue on these cars.

I'm open to any and all suggestions.

Thanks.
 

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Discussion Starter · #11 ·
Looking through the wiring diagrams I think I may be more confused than when I started. I need to poke around under the car and dash and see what wires are there and where the correspond to the computer. Also, looking at parts websites show that the crank sensor for the car is a 2 wire unit. Once I figure out what wires they are, I think I'll be able to trace back and figure everything out. Polygon's schematics are intimidating but for MOST of the engines listed it looks like Ford used the same wire colors and PCM pins. Not sure when I'll get to this, but at least I've make a step forward.
 

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You'll get nothing on coastdown doing that, the injectors already cut off at decel.

Also, crank sensor will most likely register a dtc in memory every time you kill it.

As well, using crank sensor and extra circuitry is a mistake there, the voltage signal there is very low volt (maybe 1/20th volt) and adding more resistance and especially a relay only adds to trouble in the future with signal quality. You always make low volt sensor paths as short as possible if you want no trouble out of them. The signal if two wire is an A/C one with volts both + and - so BOTH sides of the circuit may have to be opened up to kill since both signals go to PCM if wired like most mag impulse sensors.

Bad idea doing it that way.

Cut primary power to your coils, but will probably get a dtc from that too.
 

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Discussion Starter · #13 ·
I'm still not sure my injectors cut off on decel, using my scangauge reading instant MPG I never see better than 90ish MPG compared to 120ish while coasting in neutral above 50MPH or 9999 (infinite) while coasting with the engine off. I'm wondering if being a PZEV engine means no injector shut off (DFCO) because maybe there is a weird boost in emissions while in that mode. Also, I can coast farther in neutral and even with the engine on get better MPG than if I used DFCO due to the fact that the engine is slowing the car down and reducing my coasting distance, thus, requiring me to accelerate more often in order to coast less. Living in the crowded suburbs, I wish I could make better use of DFCO for slowing the car down when a traffic light changes unexpectedly.

Do the coils share a common power wire? I thought when I looked that they all were different like the injectors but I'll look again. I'm also worried that shutting off the coils could lead to a flooded situation if the injectors fire a half a second longer than coils before the computer notices the problem as more than just 1 random misfire.

Thanks for all the insight, like I said, I talked with a guy who is doing it on his Subaru using the crank sensor wire so that is just where I'm starting to look. It's beginning to look more and more like that is not the way to go on this car so I'll have to explore other avenues.
 

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As stated by amc49, the 2-wire CKP is an analogue variable reluctance sensor that unlike the 3-wire version, does not require a power source (and it's good to see amc back BTW !) Isolating both wires is a good strategy as the wave shaping circuitry inside the PCM could still pick up induced currents on a single wire. What I'm not sure is whether you should have a load resistor between the CKP terminals when disconnected to protect the CKP from energy buildup (a 2-wire CKP would remain active with engine off and car in motion).

As for the option of using the ignition coil, I guess one needs to see how it behaves when it detects a voltage drop on the primary coil that is not in line with the timing cycle. Would it still energise the HT coil and cause an early spark ? Or would the energy result in back EMF once you close the circuit again ?

It's all theoretical for me at this stage but maybe someone else has done it before and can help you further.
 

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You may indeed get a random pop misfire here or there when power is interrupted to coil, cutting power induces a spark every time it's done.

Really should just ditch the whole idea altogether..............not gonna gain much of anything there.
 

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Discussion Starter · #16 ·
Really should just ditch the whole idea altogether..............not gonna gain much of anything there.
Have to agree to disagree with you on that one. Many on ecomodder.com are using "pulse and glige" driving technique with the engine off during the coasts and are pushing 50+ mpgs. Not killing starters because they bump start the engine.

Thanks much for the technical insight, it's not falling on deaf ears but I've made up my mind on a kill switch; just need to find the best way to do it.
 

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PCM power supply diode might be the easiest place to tap in & kill power, what I don't know is if that's the ONLY power supply to the unit without a diagram. And it would still need to be in the circuit when connected, can't just get rid of it.
 

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Cut injector power itself.............
 

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Discussion Starter · #19 ·
I don't think there is a wire that powers all the injectors. Last I looked, they are kind of wired in pairs, unless farther down the line different wires merge together and supply power. I really need to get a wiring diagram for my specific car so I can know all this for sure. If I have to I guess I can wire in 2 relays and control both grounds through the switch.
 

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C2H5OH
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I'm still not sure my injectors cut off on decel, using my scangauge reading instant MPG I never see better than 90ish MPG compared to 120ish while coasting in neutral above 50MPH or 9999 (infinite) while coasting with the engine off. I'm wondering if being a PZEV engine means no injector shut off (DFCO) because maybe there is a weird boost in emissions while in that mode. Also, I can coast farther in neutral and even with the engine on get better MPG than if I used DFCO due to the fact that the engine is slowing the car down and reducing my coasting distance, thus, requiring me to accelerate more often in order to coast less. Living in the crowded suburbs, I wish I could make better use of DFCO for slowing the car down when a traffic light changes unexpectedly.

Do the coils share a common power wire? I thought when I looked that they all were different like the injectors but I'll look again. I'm also worried that shutting off the coils could lead to a flooded situation if the injectors fire a half a second longer than coils before the computer notices the problem as more than just 1 random misfire.

Thanks for all the insight, like I said, I talked with a guy who is doing it on his Subaru using the crank sensor wire so that is just where I'm starting to look. It's beginning to look more and more like that is not the way to go on this car so I'll have to explore other avenues.

Maybe understanding what your car is actually doing is the first part of the battle?
Maybe ask if you don't know?


It's called 'pumping loss'. Read about it.



I don't think there is a wire that powers all the injectors. Last I looked, they are kind of wired in pairs, unless farther down the line different wires merge together and supply power. I really need to get a wiring diagram for my specific car so I can know all this for sure. If I have to I guess I can wire in 2 relays and control both grounds through the switch.
Good idea. I've heard they can be had really cheap on ebay.



OTOH, How much are you spending on trying to accomplish this mod?
For how much of a gain?
Does that equate in an actual savings?
Or is it simply like most, a bragging right? (I get 50mpg, but spent $800 to get there)
 
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