Steve
Posted a lot
Making progress in small, easy to handle chunks of awesome
Posts: 2,034
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Sept 1, 2010 19:34:32 GMT
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Evening peeps A silly question......asked by a silly person ;D but does it matter which wire goes where when wiring up a 2-pin hall effect crank sensor? Steve
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gn3dr
Part of things
Posts: 391
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Sept 1, 2010 22:45:48 GMT
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As far as I remember it does matter - I seem to remember it having an effect on how the ecu reads the teeth - leading or lagging edge...
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As far as I remember it does matter - I seem to remember it having an effect on how the ecu reads the teeth - leading or lagging edge... ^ Pretty much that. Yes, it does matter. The ECU will probably take up for the input wave being the wrong shape but technically yes, the ECU will read the rising "edge" of the pulse, ie the sharp change in voltage, rather than the presence of a certain voltage level. Similarly to a loudspeaker in reverse, the shape of the wave will be mirrored if you hook it up backwards- I.e. it'll pull where the ECU is expecting a push. Try to find a diagram, normally these sensors and wiring are prone to interference so the wire is normally a coaxial like a TV antenna wire, the outer shield being connected to vehicle/ECU ground and the centre core being the input signal to the ECU. If it's awkward and the wires from the sensor itself are seperate to the connector plug then I'd say if one wire has a stripe that'd be my gut instinct to be the signal line. --Phil
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Last Edit: Sept 2, 2010 4:15:13 GMT by PhilA
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Gilesy
Part of things
Posts: 229
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In general, wiring the crank sensor backwards will stop the engine from running. Of all an engine's sensors, the only one with the ability to stop the engine completely is the crank sensor, and being connected the right way around is essential. When I installed the megajolt to my Mini, I connected my loom to the Ford Crank sensor and coilpack with terminal blocks with the intention that if anything was the wrong way around it's easy to swap. As it was I got it right the first time, and once the engine had run, I was happy to solder the connectors into the loom. For what it's worth, I used shielded Microphone cable from Maplins for the noise-sensitive crank sensor wiring, with the shield braid earthed at one end.
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1991 Mini Neon - Gone 1991 Polo Coupe - Gone 1987 Scirocco Scala - Gone 1991 Scirocco GTII - Gone 1980 Mini 1000 - Gone 1998 Fiesta - in flux 1999 Saab 9-5 2.3t SE - the tidy, blown Swedish modern
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Steve
Posted a lot
Making progress in small, easy to handle chunks of awesome
Posts: 2,034
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Thanks for all the input gents.......had a bit of a dumb blonde moment ;D
Basically, the engine I'm using didnt come with a plug for the crank sensor so found one off another loom(from another make) that wasnt for the crank sensor so was ive obtained the correct coloured wire to make a lead from ECU to sensor.......if i was to gut some CB antenna coaxe and somehow either feed the two wires down the middle......or remove the earth braid and wrap the wires then either heatshrink or tape up.......would that be good enough?
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Sept 2, 2010 14:14:40 GMT
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As Gilesy said, microphone cable is probably better, it has a higher impedance. That and it tends to be thinner and easier to get into a loom and through holes etc.
You'll see co-ax labeled with things like 75 Ohm and 200 Ohm- a fairly low frequency signal will pass straight down the centre core, whereas RF bounces around in the plastic gubbins in the middle off the outer braid, the metal core is only there as a 'guide'. In your case stripping back the ends a centimetre or so from the end, soldering to it and taping it up should work fine- I like to daub the ends in hot glue or varnish once they're soldered to seal them up. The outer shielding acts just like a candle wick and will draw dampness up inside the cable and cause it to corrode into green powder. Seal it up on the engine end for sure.
In short, so long as it is shielded you should be ok, but you don't need to go as wild as CB co-ax. Heck, you could use shielded network cable, it'd work just as well. (USB cables are good for this, they have a tinfoil outer shield).
--Phil
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Last Edit: Sept 2, 2010 14:17:27 GMT by PhilA
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Sept 2, 2010 14:37:42 GMT
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Up until about 1998, Peugeot/Citroens don't even have it shielded, just twisted together and insulated, so it's not massively sensitive (just don't cable tie it to the side of a HT lead or wrap 10 turns of it round your ignition coil)
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Sept 2, 2010 14:55:15 GMT
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Twisted pair helps, true- shielded is more expensive, shielded twisted pair even more so but in a situation where the vehicle is subject to a lot of noise (failing sensor, bad alternator ground etc.) there may be added benefit?
The crank sensor for my '87 Renault is shielded, so like you say, keep with what the manufacturer has specified and you can't go much wrong?
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