Crank sensor

[sawood12]

Well guess what, my car wouldn't start this morning!! The engine was turning fine but no sign of firing at all. I swapped out the DME relay but no improvement so called out the RAC. The chap from the RAC gave the engine a turn then attached a tester to the dizzy cap. Upon turning the enigne the tester confirmed there was no signal coming from the coul but just as he stopped turning the enigne over there was a flash from the tester. He turned the engine over again and the engine burst into life!! Typical. Anyway he gave the car a good look over and couldn't find anything else amis so concluded it was probably the crank sensor as the crank sensor will tell the ECU the enigne is turning so the ECU can swith on the ignition system. Does this sound right?

Also he thought the crank sensor was on top of the bell housing right behind the enigne and looked like a metal block with two leads coming from it. Is this it? It looks a real bugger to replace unless you've got small hands and arms like Mr Tickle!!

On a positive note he commented that in all his years of being an RAC man (over twenty) he had not been called out to 944's!!

 

[sawood12]

Just taking a look in the PET. Can anyone confirm that the "timing mark sender for top dead centre" part number 911.606.108.00 is the crank snsor or the RPM sensor as described in the workshop manual?

 

[zcacogp]

Scott,

Can't help specifically with your question, but if it was the CAS, why would it not work and then work - i.e. what made it decide to suddenly start playing ball?


Oli.

 

[Indi9xx]

Do you have an immobiliser fitted? This almost sounds like the classic "Old cruddy immobiliser syndrome" that I see so often

The other thing it sounds like is the ignition switch, which would be getting dodgy in the cranking position, which would explain why the coil burst into life as he let off the key.

Another option is a dodgy earth strap.. but less likely from your symptoms.

The crank sensors can go bad and can become intermittant... this is also the weather for them being a problem...

To test them you have 3 pins on each sensor, one of the pins is just for the shielding of the sensor.. the other two are for a coil winding inside the sensor, the coil winding should have a resistant of about 500 ohms to 1000 ohms... I think it should ideally be 750 ohms to 950 ohms, but I am at home at the moment so I cant check the workshop library.

So, in effect, of the 3 pins you will find that if you do a resistance check from say the middle pin to the left pin, you may find its infinate resistance (open circuit) and between the middle pin and the right pin you find its also infinate resistance however between the two outer pins (left and right), you may notice you have a resistance of say 750 ohms.. this would mean that the coil is wired to the two outer pins and the middle pin is a shielding pin.... the resistance of the coil being 750 ohms would be a sign that the coil is of good resistance.

However, if both the sensors are 750 ohms, thats not the end of the story, it could be that the leads running from the connector to the sensor is breaking down (all too common)... so if they test as ok, test them again while you wiggle the leads, you may find that if you move them about the resistance will go open circuit occasionally... this would mean the sensor needs to be replaced.

The official test is to see if you get a waveform generated by the sensor using a scope.. however, from experience, if you have a good coil resistance, you also have a waveform... unless somehow the sensor has moved away from the flywheel or unless the teeth on the flywheel have vanished.... either is unlikely.

Anyway.. I hope this rambling post on testing the sensors has been of some help

 

[sawood12]

Cheers, I do have a Cat 2 immobiliser but it appears to be functioning fine but I've also noticed that my ignition switch doesnt seem to click at the 1 and 2 positions so it is smooth and not notched when you turn the key so i've suspected that the ignition switch is a bit worn anyway. They are fairly cheap so I will probably replace anyway. I will also check the resistance on the crank sensor, but just so i'm sure i've got the sensor located - what I think is the crank sensor is positioned on top of the clutch housing behind the engine block. It has two leads - like small HT leads that bend through 90degrees and a few inches from the lead plugs there are two rectangular connectors that connect through a metal bracket. If this is the right thing then to I check the resistance from the end of the lead that looks like HT lead or the end that is a square connector?

 

[maverick996]

I've just had the crank sensor in mine replaced, as while my mechanic was having a check of all the sensors etc he moved the cable and the engine cut out! I think where the cable was held, the protective coating had worn away.

 

[Indi9xx]

Scott,

Yes, the crank sensors are behind the engine in the top of the bell housing.

You check the resistance at the plug on the lead leading to the sensor. (two sensors all in all), normally the plugs are mounted to the back of the intake manifold... black connectors on black leads.. you want to be testing the connector with the pins which lead to the sensor, not the connector with holes for the pins that leads into the main loom.

But having said all that... it seems like it is indeed your ignition switch which is at fault!

 

[sawood12]

I'll be replacing the ignition switch as a matter of course but I do get all the lights on the dash illuminated when I turn the key and everything else electrical works so does that indicate that although the switch is worn it is still making the electrical circuit?

Aparently you can also get a multimeter across the terminals to measure voltage while the engine is cranked over, you should be getting around 3.5v ac so that'll be a little job over the christmas period!!

Has anyone replaced the crank sensor? It looks like a real pig to get to and with the weather as it is I'm not sure I have the patients or the intention to get under the car!! - Boy i'm really getting lazy with my DIY car mechanics these days. It was so much easier when I had access to a large heated double garage with all the tools I could ever need at my disposal. I'm getting soft in my old age!!

 

[charles.y]

I had the same problem 12 months ago while I was accelerating hard on a slip road leading into the M25 and the engine just suddenly stop revving.

Tried all the usual tests incl. DME relay, immobilizer etc but no luck. Called RAC and they tested that there is no elec. current comes out of the coil. Dartford Tunning has finally verified the cause was by a loose crank sensor.

Charles

 

[sawood12]

Charles - I decided to do a pre-emptive strike and bought a new crank sensor. Given that the symptoms I am suffering are classic for a dodgy crank sensor I thought best to replace the ageing sensor and be done with it. I went to replace the sensor earlier this evening and guess what..... my crank sensor was also loose!! I never thought to check it. I've tightened it and will see how I get on. How on earth does the bolt loosen - is it though engine vibration? I'm pretty sure that during the cars previous ownership the sensors have been removed or replaced at some stage because the speed sensor plug is not attached through the mounting bracket and is connected above the bracket so the speed sensor has definately been disturbed or replaced at some stage in the cars past.

Oh well i'll have to see how I get on over the next few weeks or so to get my confidence back in the cars starting reliability. I've also got a new ignition switch to replace my worn current one. Hope I can draw a line under this little debarcle, but as a word of warning to all 944 drivers, if you get intermittent starting problems check your crank and speed sensor bolts!!

 

[peanut]

I have a no start problem too. Had it for weeks. It would appear to be no fuel delivery.
I am suspecting my crank sensor now too. I aim to try trace the wiring from it today so I can test the resistance hopefully . I believe it is just a magnet and the distance from the magnet to the flywheel is quite critical. The further the gap the weaker the signal to the DME apparently
The only thing stopping me sending mine to the local garage is they will wreck the spoilers getting it on and off their trailer.[]

My starter has always been a bit aggressive and the engine gets shook about a lot I'm wondering if that has effected the gap on the sensor ? maybe loosened the bolt ?

glad you got yours sorted and not too expensive neither[]

 

[Bridge944]

My car died with a crank sensor problem yesterday afternoon in Morrison's car park Bridgwater, the car is in Honiton being repaired as we speak. My wife (who was with me at the time was very impressed - not!!).
We were happily fielding questions about the car from shoppers until the tow truck arrived and then they left with knowing looks and smirks on their faces.
Hope you car is running well now - I should get my car back this afternoon.
Incidentally my previous Lux had the same issue during my ownership

 

[924nutter]

Re signature, unless you happen to have a Turbo Cab!

 

[peanut]

ORIGINAL: Bridge944

[FONT=arial"]My car died with a crank sensor problem yesterday afternoon in Morrison's car park Bridgwater, the car is in Honiton being repaired as we speak. My wife (who was with me at the time was very impressed - not!!).
[FONT=arial"]We were happily fielding questions about the car from shoppers until the tow truck arrived and then they left with knowing looks and smirks on their faces.
[FONT=arial"]Hope you car is running well now - I should get my car back this afternoon.
[FONT=arial"]Incidentally my previous Lux had the same issue during my ownership

I don't believe it ! I was working in Bridgewater yesterday and went past Morrisons several times . small world isn't it. I saw your 944 last week going down the Taunton road and forgot to mention it.
Sorry to hear you had to get recovered.
Any verdict on the fault yet ? I'm psyching myself up to go out and start checking mine over.
When I get the chance I'm going to collate all the various threads and guides and schematics relating to non starting and construct a flochart checklist to help other owners with this problem.

Time and again It appears to be lack of regular use that is the problem.

Incidentally I also saw a gorgeous black speedster broken down in the MRI layby the other evening on my way home. Apparently the owner also lives locally. perhaps you may have seen it around?

 

[944Turbo]

ORIGINAL: peanut

I have a no start problem too. Had it for weeks. It would appear to be no fuel delivery.
I am suspecting my crank sensor now too. I aim to try trace the wiring from it today so I can test the resistance hopefully . I believe it is just a magnet and the distance from the magnet to the flywheel is quite critical. The further the gap the weaker the signal to the DME apparently
The only thing stopping me sending mine to the local garage is they will wreck the spoilers getting it on and off their trailer.[]

My starter has always been a bit aggressive and the engine gets shook about a lot I'm wondering if that has effected the gap on the sensor ? maybe loosened the bolt ?

glad you got yours sorted and not too expensive neither[]

I think if you have spark but no fuel it wont be the crank sensors,
Tony

 

[Panzer944]

Just looked under bonnet and noticed that there appears to be a sensor dangling loose on a cable near the clutch bellhousing (right side of engine as you look at it from the front - ie 'nearside' side) ... car still starts ok and runs ok ... but have noticed lumpy idle with a tad more vibration recently.

New cylinder head/gasket/belts/pulleys/engine mounts/air metering unit/distributor/injectors about 10,000 miles ago (ouch!) - unlikely they are causes of idle lumpiness (idle set at 750-800 rpm - is that about right?).

Obviously, I'll get it seen too - just wondered if it was a common failing and, in terms of 'cause and effect' could its dangling around the engine bay have anything to do with the lumpy idle. Off to find my Haynes manual and see where it goes - any ideas?

 

[charles.y]

I had a loose crank sensor happened to me 2 years ago while I was driving at about 50 mph - not quite a good experience. I think other owners in this forum also had experienced this. Is it common?

 

[Panzer944]

ORIGINAL: Panzer944

Just looked under bonnet and noticed that there appears to be a sensor dangling loose on a cable near the clutch bellhousing (right side of engine as you look at it from the front - ie 'nearside' side) ... car still starts ok and runs ok ... but have noticed lumpy idle with a tad more vibration recently.

New cylinder head/gasket/belts/pulleys/engine mounts/air metering unit/distributor/injectors about 10,000 miles ago (ouch!) - unlikely they are causes of idle lumpiness (idle set at 750-800 rpm - is that about right?).

Obviously, I'll get it seen too - just wondered if it was a common failing and, in terms of 'cause and effect' could its dangling around the engine bay have anything to do with the lumpy idle. Off to find my Haynes manual and see where it goes - any ideas?

Just checked with torch and Haynes manual and both flywheel sensors are in their place - so this dangly sensor is obviously not one of them ... it's about one and a quarter inches long about half an inch in diameter with apparently dissimilar materials (metals?) both circular in section, one insde the other (ie annular) when looked at 'end-on' ... there is a black plastic casing about 5/8" diameter at the other end with the connection wire(s) - this plastic has had some damage to it - no evidence of mounting hole or screw thread etc etc (although that may have been on the broken bit?). The connecting wire(s) is/are covered in a light grey plastic conduit about quarter of inch diameter and seems to disappear round the back of the cylinder head towards the off-side of the engine. Sorry to be so vague ... anyone got a clue? I will try to upload a photo but being a newbie I don't (yet) know how to do that! Any help/suggestions gratefully received - car now running fine to be honest - ho hum.

 

[peanut]

if its anything like my S2 that cylinder should clip into a plastic clip bracket at the top rear of the head on top of the connector for the other sensor.
Follow the cable for both the sensors and they should end up at the same place, clipped on a bracket together one on top of the other.
Can you get a picture of yours ?
If you go to the photoshop website and join you can upload your pictures there for free and they host them for you free.
Its a simple matter of copy pasting the url to your post on here.

 

[edh]

02 sensor?