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Crank signal question.

 
Old 04-23-2017, 04:01 PM
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Default Crank signal question.

I am helping a friend with his racecar and we cannot get the car to run correctly. I think it is a faulty crank sensor. I am attaching a screen shot of the sensor graph from the ECU diagnostics. I have never seen a curve shaped like this. Does this look normal at all?

Details about the car:
034 Motorsports ECU
1.5 Honda, non V-Tec motor
Jenvey Crank sensor

if this car had a Megasquirt I would know more about this, but it is not. Any thoughts on the graph(Ok, fixed the graph... why didn't anyone tell me it wasn't showing up, lol)?

Last edited by MX5RACER; 04-24-2017 at 11:26 AM. Reason: Just checked the post from another PC... no graph, re-attaching the graph.
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Old 04-24-2017, 11:29 AM
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Let try this one more time.
DAMN IT... I cannot get the picture attached...
Attached Thumbnails Crank signal question.-img_2312.jpg  
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Old 04-25-2017, 08:37 AM
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This does not look like any can signal I've ever seen. What type of crank sensor is this supposed to be? Hall, VR, other?
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Old 04-25-2017, 11:17 AM
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From what I can gather, I believe it is supposed to be a VR sensor. I would think the car would not run at all with a signal like that, but it runs, just not very well.
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Old 04-25-2017, 11:24 AM
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How certain are you that what we're looking at in this image is really the analog signal from the crank sensor? is this an external Oscilloscope hooked up, or is this output from the ECU? I assume the x-axis on the graph is time. The y-axis would be Volts, mV, what scale?
Afaik, most ECUs will just use some sort of IC or other circuitry to condition the CS signal, so all the ECU should see is a square wave, which leads me to assume that this is an external scope. On the other hand, the inserted red line looks like an ECU interpreting the signal. Dunno. Please provide links to information on the setup you're using here. Without knowing what we're looking at, diagnosing is going to be tricky.
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Old 04-25-2017, 11:35 AM
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This is the diagnostic section in the ECU software. I assumed the Yellow line was the sensor value data and the Red was the ECU square wave. This is with the car only cranking. The RPM's make sense in that they show ~260rpms or so. As soon as you stop, the RPM reading goes to 2209 as seen in the screen shot above.

The ECU is a very old 034Motorsports ECU.
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Old 04-25-2017, 01:22 PM
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Those oscillations are very weird and I'd guess that they may have to do with the "running like crap" issue you're experiencing. It does seem, however, that your sensor is working- a VR sensor is pretty hard to kill and since you are getting a signal that does seem to make some sense, my gut-reaction is that the oscillation is generated by some signal-conditioning circuitry in your ancient ECU.
Any chance you can remove the sensor and ECU and bench-test the setup? Why use an ECU that is no longer supported for a new setup?
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Old 04-25-2017, 01:42 PM
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Not a new set-up. This is what was existing in the car when he bought it. We are almost to the point of punting and putting a megasquirt in it etc.
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Old 04-25-2017, 02:20 PM
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Originally Posted by MX5RACER View Post
Not a new set-up. This is what was existing in the car when he bought it. We are almost to the point of punting and putting a megasquirt in it etc.
That sounds like a good plan... i.e. replacing an ecu that no one is really familiar with for one that has pretty good support both from the folks that make them and from the customer base.
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