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 Post subject: Cam and crank position sensor operation
PostPosted: Mon Dec 26, 2011 10:15 pm 
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I need schooling on how the cam and crank position sensors operate and how they relate to coil pack operation. From what I've read, the ckp is a 5v sensor and the cmp is a 8v sensor correct? What is the output of these? They just send a 5v or 8v signal to the computer when triggered right? How does the computer know what coil to fire?

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Mon Dec 26, 2011 10:34 pm 
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Cam sensor is basically a magnet, the crank sensor is a toothed wheel with a gap. The gap signals 1 rotation. Each tooth is a specific amount of rotation from that gap, so it knows within a relatively high degree of accuracy where each piston is at all times.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Mon Dec 26, 2011 10:44 pm 
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Chris Barnett wrote:
Cam sensor is basically a magnet, the crank sensor is a toothed wheel with a gap. The gap signals 1 rotation. Each tooth is a specific amount of rotation from that gap, so it knows within a relatively high degree of accuracy where each piston is at all times.


So it sends a signal every time it sees a gap?

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I'm trying to figure out how to use the stock sensors and coil pack in an older car is why I'm asking. Trying to figure out how the sensors work and trigger the coils so I can figure out a way to get the older computer to read them.

Cam sensor sends a signal every time it sees a magnet?

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 2:28 am 
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Are you swapping to a neon engine, or converting a different engine to a neon PCM?

Makes a HUGE difference. If converting, the engine you're using needs the exact same crank orientation. And then you'd have to adapt the OEM neon crank trigger wheel to that crank. Seems 10,000 times easier to go with a megasquirt.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 2:43 am 
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Force Fed Mopar wrote:
I'm trying to figure out how to use the stock sensors and coil pack in an older car is why I'm asking. Trying to figure out how the sensors work and trigger the coils so I can figure out a way to get the older computer to read them.
No need to get your old computer to read them.

How does your old computer work - how does it know where the crank and cam are and when to fire the plug - and pulse the fuel if you are not carbed or using a constant flow throttle body injector. I am assuming it does not use a distributor..


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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 3:05 am 
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Better yet: What EXACTLY are you trying to do?

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 6:16 am 
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The PCM interprets the signals and then triggers the coil/injectors. The crank/cam sensors don't directly do it.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 8:30 am 
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I'm putting a '97 2.4 Stratus engine into my '87 Daytona. The original 2.2 uses a HEP sensor in the distributor to determine cam and crank position.

chipdogg wrote:
The PCM interprets the signals and then triggers the coil/injectors. The crank/cam sensors don't directly do it.


Does it just count the crank trigger signals and fire each coil accordingly? Cam sensor have 2 or 4 magnets on it? I'm thinking 4 if it is sequential injection.

What I'm trying to figure out is whether or not the cam/crank position sensor signals can be read by my original computer, with some code changes if necessary. I'm working on it with a guy that knows the code and how to modify it, we just need to know exactly how it works. I'm going to have to add a coil driver I know, as the LM/PM setup only has one. The other guy wasn't sure if the sensors just sent a trigger signal or if they did something else.

If they simply put out a trigger signal every time they are activated, I'm pretty certain we can make it work.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 11:28 am 
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Get a 1995 thru 2002 Stratus / Breeze (or anything with a pre 2002 Dodge / Plymouth / Chrysler 2.4L DOHC engine in it) factory service manual and reference section 8D. That section tells all about the crank and cam position sensor and how they count pulses.

There also are diagrams of the pole position of the target magnet. The target magnet diagram may be important to you.


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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 11:30 am 
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The 2.2 and the 2.5 used Hall Effect sensors in the distributors. The crank sensor in the 2.0 and the 2.4 is a hall effect sensor. The one big gap in the crank trigger wheel is basically tdc, the rest of the notches are at certain degres to correspond to the relative pistons position. The cam sensor uses one magnet. It has north/south poles embedded into it, of varying lengths. One of them is bigger than the others, to differentiate tdc. The pcm sees the signals generated by these sensors, and makes the adjustments accordingly. Ohio's post that just appeared before i posted this has good info.

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Last edited by MichNeon on Tue Dec 27, 2011 11:53 am, edited 1 time in total.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 11:40 am 
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Thanks guys, I'll try and get a hold of the FSM. Maybe Mitchell-On-Demand has it too, I have access to it.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 1:16 pm 
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Thanks for the PM OhioHomesteader!

Have another question though, It seems that the FSM says the ckp and cmp sensors are 5v sensors. On Mitchell-On-Demand, it lists them as 8v (I looked them up under '97 Stratus 2.4). I'm more inclined to believe the FSM, can anybody verify that? I don't have a car handy to put a scanner on and see what it is.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 3:45 pm 
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I just looked on Techconnect, for the '97 Stratus 2.4, the pcm supplies 8 volts, the sensors switch from low (0.30 for the cam, .5 for the crank) to high (5.0 for both).
Techconnect is the Chrysler corporate website for dealer techs.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 6:29 pm 
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Ah, so it has a 8v power supply but puts out a 5v signal.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Tue Dec 27, 2011 6:47 pm 
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Force Fed Mopar wrote:
Ah, so it has a 8v power supply but puts out a 5v signal.


On the high end, yes.

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 Post subject: Re: Cam and crank position sensor operation
PostPosted: Fri Dec 30, 2011 9:31 pm 
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The cam/crank use an 8v reference meaning that the signal is either pulled to ground or 8 volts as the hall affect switch flips between a high and low signal.

The "5volts" is a test voltage put out by the PCM on the signal circuit to determine if the signal circuit is properly wired to the sensor. If the computer sees 5 volts on ANY signal wire whether it's TPS, CMP, or VSS regardless of the reference voltage, the computer will assume that the circuit is incomplete. This can mean unplugged, faulty sensor or incomplete path from the sensor to the PCM.

You will see 5 volts on most any "signal" circuit when testing at the sensor connector, unplugged. When you plug it back in with the key on then you should see the voltage drop down to a reading that accurately describes the condition of the sensor in question.

Force Fed, Do you have a 1987 FSM wiring diagram manual for your car? I've got one if you're interested, hit me up via PM.

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