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Old 8th March 2020, 08:28   #1
Steve42
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Default crankshaft sensor

hi all.
would a crankshaft sensor behave the same way as a camshaft sensor.
that is when hot will stop the car from starting but when cold runs fine.
had problems yesterday with the zt not starting after been run for about 10 miles.stopped to put petrol in and would not restart. after turning over loads it did fire up. but after a few yards cut out.restarted and drove away fine. but again cut out after around 500 yards. got it started and had to rev it up to 4 thousand to keep it running. after around half a mile got home and it was starting up fine and tick over was spot on.
just put the snapon code reader on and the error was crankshaft sensor but zt started first turn. i thought if the crankshaft sensor was faulty car would not start.

thanks
steve
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Old 8th March 2020, 10:11   #2
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Sounds like a crank sensor issue, but there's an easy test.
This sensor drives the rev counter, so when cranking the needle should rise a little from the off position. It should react to each pulse from the flywheel's rotation. If there's no rev counter movement, the crank sensor is faulty.

The crank and cam sensors operate through the Hall Effect, which relies on a magnetic field from a permanent magnet on the sensor's tip. Failing magnets lose some magnetic flux when hot and regain it on cooling. They'll eventually lose enough flux to stop working.. This is reflected in the way these sensors respond to engine temperature as they deteriorate.


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Last edited by T-Cut; 8th March 2020 at 10:13..
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Old 8th March 2020, 14:32   #3
Yorkshire GOC
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I think the Cam Sensor failing will cause only non starts - a failing crank sensor will cause both non starts and cut outs - as T-Cut says a simple test is does the Rev Counter move on cranking.
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Old 8th March 2020, 22:20   #4
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My V6 failed to start when hot, and it had logged fault codes relating to the camshaft position sensor. I replaced it, and there are no more codes, nor failure to start when hot.

I've always wondered about the rev counter. Mine just sits at the bottom when I crank - it only jumps up as the engine actually catches and I can let go of the key. Never seen this movement on cranking...
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Old 9th March 2020, 00:04   #5
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Thanks all,
Have had a cam sensor go a couple of times now .and was ok once cold.
Didnt know if the crank sensor was the same.
Didnt look at the rev counter at the time as to busy trying to start up and move out of the way of the traffic lights.
But my snap on ethos diagnostic comes back as crank sensor fault. Now on order so guess what job I am doing this week.

Thanks all for the info

Steve
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