Do you know what the actual failure mode is?
Testing it?
Or does it get dirt on it which can be cleaned off?
Ideas please. Renault Scenic 2002 16v petrol not starting.
- Thread starter Agile
- Start date
Do you know what the actual failure mode is?
Testing it?
Or does it get dirt on it which can be cleaned off?
Sponsored Links
Crank sensors are weakest point on modern engines, they do start playing up, effected by temperature, dirt and age, since they work on a magnetic reluctance principle, their operation depends on all of above parameters, gaps etc, strength of permanent magnet weaken with age and heat, so the signal they produce can fall off and signal is also proportional to speed, for example when engine is only at cranking speed, the signal is at its weakest, (same as in a principle of electromagnetic generator, the slower the RPM, the lower the output voltage, the faster the speed of the engine, stronger will be the signal, so this is why starting is always a problem on a weakened and aging sensor) I have had similar problem with my Vauxhall, where I found I needed to change these sensors around every 3 to 5 years inetervals, as well as the cam sensor, and yes this sensor would initiate firing sequence in modern cars, i.e. fuel pump relay , ignition circuit, etc.
Passive types: They usually have 3 wires, a shield and the pair going to the inductive coil.Often the shield wire is common so some only have two wires. Signal is processed in the ECU.
Active type: Uses a pre-amplification, and converts weak sine wave into a squared wave digital pulses of around 5v (TTL) and these are more reliable, and need a +5v and a ground and one output, so again it will have 3 wire lead.
For further information check this site where you can get more useful info from : http://www.motionsensors.com/speed-...dwQF5JnorXvyzDtdaFIEAdacB4W6agFjY2RoCsoTw_wcB
extract from above:
Variable Reluctance (VR) sensors offer a unique solution to many system measurement problems by providing an uncomplicated, accurate, reliable, versatile counting device.
A variable reluctance sensor is composed of a winding wound around a cylindrical magnetic material, typically made of some type of ferrous material that is referred to as a pole piece. A magnet is attached behind the pole piece, creating a magnetic field through the pole piece and winding. This magnetic field projects out from the pole piece front, also known as the sensor tip. When ferrous material passes through and disrupts this magnetic field, electricity (a sine wave) is generated. They are passive devices and do not require any external source of power to generate a signal.
Therefore, when the tip of the sensor is placed near a moving or rotating device made of ferrous metal such as a gear or rotor, a simple technique for measuring rotational speed is created. The frequency of the signal is directly proportional to the speed of rotation. The amplitude of the signal is affected by the speed of rotation, the material being sensed and the distance, known as the "air gap", between the sensor tip and the rotating object.
Most manufacturers of magnetic sensors base their design on having very small air gaps of .005" to .015". Increasing the size of this gap produces a fall-off of signal voltage. In practical application, such small gaps could be hazardous, especially if the object being sensed is not concentric or tends to have a loss of concentricity with increased speed or motion. MSI's Premium line of VR sensors employ a special "focusing tip" which enables the sensor to operate at larger gaps in excess of .060". The closer the sensor is to the object being sensed, the greater the amplitude. MSI sensors however, allow the sensor to be farther from the target without rapid signal deterioration as in other sensors.
Motion Sensors also manufactures a variation of variable reluctance sensors known as inductive magnetic sensors. These differ from standard VR sensors in that the magnet is not in the unit, but in the object being sensed. They are used when the rotating device sensed cannot be made of ferrous materials. For instance, if the target to be sensed is made of nonmagnetic stainless steel, brass, aluminum or plastic, a centerpole magnet may be placed in the center of the rotating device. Alternatively, magnets can be imbedded (equally spaced) into the target's outer rim or diameter. Inductive sensors will sense the magnetic fields and produce a signal. They are also designed to provide this capability at air gap distances substantially greater than standard VR sensors, as would be required for centerpole magnet locations.
In summary, variable reluctance sensors convert mechanical motion to electric energy without direct contact when positioned near a turning rotor, gear, shaft or other regularly moving device. The output signal can be fed into a digital counter, totalizer, analog converter, tachometer, overspeed or underspeed control, oscilloscope, or other monitoring and control device. The sensor provides a simple, reliable, inexpensive transducer for highly sophisticated control systems.
Passive types: They usually have 3 wires, a shield and the pair going to the inductive coil.Often the shield wire is common so some only have two wires. Signal is processed in the ECU.
Active type: Uses a pre-amplification, and converts weak sine wave into a squared wave digital pulses of around 5v (TTL) and these are more reliable, and need a +5v and a ground and one output, so again it will have 3 wire lead.
For further information check this site where you can get more useful info from : http://www.motionsensors.com/speed-...dwQF5JnorXvyzDtdaFIEAdacB4W6agFjY2RoCsoTw_wcB
extract from above:
Variable Reluctance (VR) sensors offer a unique solution to many system measurement problems by providing an uncomplicated, accurate, reliable, versatile counting device.
A variable reluctance sensor is composed of a winding wound around a cylindrical magnetic material, typically made of some type of ferrous material that is referred to as a pole piece. A magnet is attached behind the pole piece, creating a magnetic field through the pole piece and winding. This magnetic field projects out from the pole piece front, also known as the sensor tip. When ferrous material passes through and disrupts this magnetic field, electricity (a sine wave) is generated. They are passive devices and do not require any external source of power to generate a signal.
Therefore, when the tip of the sensor is placed near a moving or rotating device made of ferrous metal such as a gear or rotor, a simple technique for measuring rotational speed is created. The frequency of the signal is directly proportional to the speed of rotation. The amplitude of the signal is affected by the speed of rotation, the material being sensed and the distance, known as the "air gap", between the sensor tip and the rotating object.
Most manufacturers of magnetic sensors base their design on having very small air gaps of .005" to .015". Increasing the size of this gap produces a fall-off of signal voltage. In practical application, such small gaps could be hazardous, especially if the object being sensed is not concentric or tends to have a loss of concentricity with increased speed or motion. MSI's Premium line of VR sensors employ a special "focusing tip" which enables the sensor to operate at larger gaps in excess of .060". The closer the sensor is to the object being sensed, the greater the amplitude. MSI sensors however, allow the sensor to be farther from the target without rapid signal deterioration as in other sensors.
Motion Sensors also manufactures a variation of variable reluctance sensors known as inductive magnetic sensors. These differ from standard VR sensors in that the magnet is not in the unit, but in the object being sensed. They are used when the rotating device sensed cannot be made of ferrous materials. For instance, if the target to be sensed is made of nonmagnetic stainless steel, brass, aluminum or plastic, a centerpole magnet may be placed in the center of the rotating device. Alternatively, magnets can be imbedded (equally spaced) into the target's outer rim or diameter. Inductive sensors will sense the magnetic fields and produce a signal. They are also designed to provide this capability at air gap distances substantially greater than standard VR sensors, as would be required for centerpole magnet locations.
In summary, variable reluctance sensors convert mechanical motion to electric energy without direct contact when positioned near a turning rotor, gear, shaft or other regularly moving device. The output signal can be fed into a digital counter, totalizer, analog converter, tachometer, overspeed or underspeed control, oscilloscope, or other monitoring and control device. The sensor provides a simple, reliable, inexpensive transducer for highly sophisticated control systems.
Last edited:
Sorry, no. But if you can get it to someone with a code reader it may be stored in the memory. Definitely worth unplugging and cleaning the connector to it though.
Undo the sensor and see that it's not covered in clutch dust.....give it a wipe and try again. Unfortunately these things don't always throw up a fault code because the engine doesn't actually start 
. New crank sensors are around the £20 mark, genuine.
John
. New crank sensors are around the £20 mark, genuine.John
Sponsored Links
Over the last few days it has always started although not always immediately and so I have lost confidence in it and not used it for the clean journies that I bought it for.
Restarting after it has run usually but not always is immediate. Could I take that to eliminate the likelihood of petrol starvation?
Certainly I need to remove the crankshaft sensor and look at that.
Thanks for your suggestions.
Restarting after it has run usually but not always is immediate. Could I take that to eliminate the likelihood of petrol starvation?
Certainly I need to remove the crankshaft sensor and look at that.
Thanks for your suggestions.
We're all just guessing somewhat, Tony......typical crank sensor failure is to allow a cold start, but not a hot one until things have cooled down a bit. I've never had a faulty one that caused the vehicle to cut out though - once its running it tends to stay that way.
Unfortunately, nothing will happen if this sensor has called it a day as it is a primary player in providing information to the engine ECU.
Generally they are located on the top of the gearbox bell housing, close to the flywheel. If it was me I'd take a gamble and renew it - but there again, I'm very good at spending other folks' money
John
Unfortunately, nothing will happen if this sensor has called it a day as it is a primary player in providing information to the engine ECU.
Generally they are located on the top of the gearbox bell housing, close to the flywheel. If it was me I'd take a gamble and renew it - but there again, I'm very good at spending other folks' money
John
with modern cars (yours) stick a code reader on it. You'll be surprised, every man and his dog has one of these gizmos so ask around! You can buy basic ones for under £20 or better ones ( I paid £250 for mine) for more money. Once you have the code/s if any, they wont tell you whats wrong but will give you clues. Armed with the codes, start googling them and trawling owners forums and you'll likely arrive at whats wrong...
Certainly do that, but simple resistance tests do not always show other weaknesses within the sensor such as the magnetic strength, test may show OK, etc.
And you are right about using a car that can cut out any time in the middle of traffic whilst rolling or whilst stationary at traffic lights. Perhaps a proper way to test a crank sensor would be in a test jig with ideal engine operating conditions and bearing in mind the gaps between the crank sensor head and the cogged wheel.
All the senors that I had replaced on my car tested OK on a resistance range, as new sensors did.
My car put me in a very dangerous and compromised situation once, on Vauxhalls engines, crank sensor starts to play around intermittently, car starts ok from cold, once it has reached normal temperature, it is still kind of Ok when driving along, every now and then it may throw a tantrum, you might get an odd back-fire and jerk, (this is due to sensor missing pulses and sending a spark at a wrong time) but as the car is rolling it recovers from it and continue running, but problem occurs mostly when you have pulled at red lights as the engine is only idling, at this slow engine speed the crank signal is much weaker, and when the sensor misses detecting a pulse, tends to kick back, (incorrect timed spark, far too advance) and causes engine to cut out and there after no restart is possible until left to cool down sufficiently, that could take up to 5 minutes!
Once I was caught in a middle lane on a busy section of A4, I pulled at red lights, the engine decided to cut out on me, it wouldn't restart, lots of back fires! I waited and waited but it would not fire, I had to use my Emergency hazards to warn fellow driver stuck behind me, I was in a very awkward position, (middle lane) I had to wait there for at least 10 minutes for the engine to cool down sufficiently to allow it start again, however the danger came when lights went green, other traffic started to move on in the other two lanes, traffic stuck behind me realised I am not going anywhere, drivers behind me started to pull out, some into left lane and others into right lane to pass me, one driver didn't quite pull out safely, he nearly caused a bad accident, as he failed to see a fast approaching car, that had to screech to a halt to avoid a collision, nearly caused a massive crash! and would have left me guilty! then there were all these other drivers when the lights went red again, many in middle lane were still pulling behind my car, knowing that i am broken down and have my hazards on, some pulled right close behind me as if I would be moving away again when the lights go green! but my car was going no where! toots all over, drivers cursing and frustrated, you just pray that it never happens to you. No one has any patient these days, cause they are all driving new BMWs Mercs, and Audis, they have no time for vauxhall drivers! and for being a Renault driver, God help you!
With diagnostics equipment, it may not always tell if a crank sensor is faulty, or intermittent, since each time you plug one in, it always throws a crank sensor code since during diagnostic the engine isn't running so the diagnostic adaptor always throws a crank sensor fault, unless a more sophisticated diagnostic can do the check whilst engine is running.
Last edited:
I do actually have a code reader but have not used it yet. About £80 on Ebay.
When I started to try it asked me for a "garage number" and I did not know what to enter. Anyone have any ideas?
Now I have ordered an unbranded crankshaft sensor as it was only £5.45 Was that false economy? With two of these cars a spare would not go amiss.
I did consider just changing the sensors over but reluctant to disturb too much or might end up with two faulty cars!
Any comments please?
Tony
When I started to try it asked me for a "garage number" and I did not know what to enter. Anyone have any ideas?
Now I have ordered an unbranded crankshaft sensor as it was only £5.45 Was that false economy? With two of these cars a spare would not go amiss.
I did consider just changing the sensors over but reluctant to disturb too much or might end up with two faulty cars!
Any comments please?
Tony
As for getting stuck, at Archway North London they have redesigned the junction with only a SINGLE lane to handle all the traffic including a lot of busses. Very difficult if your car stalls or even runs out of petrol.
Hi Agile,
Just now signed up, actualy not only to offer advice about your car, but also to ask you about your old Potterton Diplomat 41-48 Boiler post.(That post appears retired)
But first about your car, here is my 2pence worth. (At a quick skim you seem to have got some spot-on advice so far.)
1. From past experience a 'test by substition' trumps all other tests as it leaves little room for doubt, even better than throwing in a part off shelf because you know 100% that the part works (provided you dident beak it of course). I also just ran this by my mechanic friend tonight and its also what he would do in your situation
2. If substitution test indicates it was the crankshaft sensor, then I would replace with genuine if cost is only 20 GBP, unless you were really pinched, because as you said you dont want to get stuck up one way North London ' Creek' without a padlle.
Lastly about your old Poterton, I have one too and propably last man standing? From your posts I think you may have decomissioned it? Do you still have it by any chance? or spares? I would like back up of gas control parts including solenoid,(or know where to source them) plus I will need to have a go at cracking those 'stud n nuts' this summer to stop a seeping gasket leak. I read with interest some unkind comments about the 'old Lady' on your thread, however, being as my boiler is situated in a double length underground garage, boiler 'inefficiencey' keeps the damp out which is a huge bonus for me (and cosy too for winter man cave! hords of mice used to think so too until they were evicted) Plus, as energy laws dictate, what goes in must come out and doesent just disappear, so some of that 'lost' heat rises to warm structures above garage... plus heat from the internal flue is partialy recaptured as it passes up 2 floors plus a 3rd if you count the attic.
There is potentail if I could figure it out, to have an improved heat exchange factor from that flue, just 'pipe' dreams I suppose?
Any way I hope you get your wheels 'a rollin' soon and hope you may still have some parts of your old Poterton Diplomat remaining and I would like to know what eventualy happend to it as that old thread seems to have died.
Just now signed up, actualy not only to offer advice about your car, but also to ask you about your old Potterton Diplomat 41-48 Boiler post.(That post appears retired)
But first about your car, here is my 2pence worth. (At a quick skim you seem to have got some spot-on advice so far.)
1. From past experience a 'test by substition' trumps all other tests as it leaves little room for doubt, even better than throwing in a part off shelf because you know 100% that the part works (provided you dident beak it of course). I also just ran this by my mechanic friend tonight and its also what he would do in your situation
2. If substitution test indicates it was the crankshaft sensor, then I would replace with genuine if cost is only 20 GBP, unless you were really pinched, because as you said you dont want to get stuck up one way North London ' Creek' without a padlle.
Lastly about your old Poterton, I have one too and propably last man standing? From your posts I think you may have decomissioned it? Do you still have it by any chance? or spares? I would like back up of gas control parts including solenoid,(or know where to source them) plus I will need to have a go at cracking those 'stud n nuts' this summer to stop a seeping gasket leak. I read with interest some unkind comments about the 'old Lady' on your thread, however, being as my boiler is situated in a double length underground garage, boiler 'inefficiencey' keeps the damp out which is a huge bonus for me (and cosy too for winter man cave! hords of mice used to think so too until they were evicted) Plus, as energy laws dictate, what goes in must come out and doesent just disappear, so some of that 'lost' heat rises to warm structures above garage... plus heat from the internal flue is partialy recaptured as it passes up 2 floors plus a 3rd if you count the attic.
There is potentail if I could figure it out, to have an improved heat exchange factor from that flue, just 'pipe' dreams I suppose?
Any way I hope you get your wheels 'a rollin' soon and hope you may still have some parts of your old Poterton Diplomat remaining and I would like to know what eventualy happend to it as that old thread seems to have died.
Sorry Agile, when I commented about your flywheel sensor I mixed up and thougt it was you who was also the OP on another thread (re 'Ancient but reliable Potterton Diplomat 41/48 kettling' Discussion in 'Plumbing and Central Heating' started by rissole, 7 May 2011.)
Anyhow, no point in me posting there because OP has not been here since 2011, but if you know of any boiler graveyard or anywhere where I can salvage some parts please let me know.
Thanks
Anyhow, no point in me posting there because OP has not been here since 2011, but if you know of any boiler graveyard or anywhere where I can salvage some parts please let me know.
Thanks
Thanks for suggestion Tony, being new to the forum I wasent sure if I could post links yet, Old Boiler link is below. Did you decide yet what to do re your Renault crankshaft sensor? If you have any other questions and post them up I can see what my mechanic friend suggests.
https://www.diynot.com/diy/threads/...diplomat-41-48-kettling.273721/#ixzz4ccBF5CgE
For my one I think the solonoid may be intermitently not fully closing and 'letting by' because very occasionaly water has overheated to extreme temperature. Its happened twice now in last 6 months. I have an old spare solenoid which I kept when I had it changed, because it was noisy, some 20 years ago (...the replacement was just as noisy.) I suppose I could have that re-fitted or better still if there was was a more 'silent' alternative solenoid with same spec? that would be just the ticket.
I found reference to 'obselete'parts here
https://www.baxiboilerparts.com/content/images/boilerdiagrams/diplomat_20-26_1.2.jpg
Potterton part number 40229201
OBSOLETE Solenoid Valve Kit 1/8in BSP 240v
Found 1 part:
OBSOLETE SOLENOID VALVE KIT 1/8IN BSP 240V
Manufacturer: Potterton
Part GC No.: 358-855
Manufacturer Code: 40229201
Part Type: SOLENOID
Fits Appliance(s) GC No.
DIPLOMAT 30/34 BASIC(SPERRYN)HW&SW - 41-590-20
DIPLOMAT 30/34 SB(SPERRYN) - 41-590-25
DIPLOMAT 35/40 BASIC (SPERRYN) - 41-590-21
DIPLOMAT 35/40 SB (SPERRYN) - 41-590-26
DIPLOMAT 41/48 BASIC (SPERRYN) - 41-590-22
DIPLOMAT 41/48 SB (SPERRYN CONTROL) BOILER - 41-590-27
Yes I might risk getting laughed at and start a thread as you suggested... in a few days when I will have more time to answer responses
Patrick
https://www.diynot.com/diy/threads/...diplomat-41-48-kettling.273721/#ixzz4ccBF5CgE
For my one I think the solonoid may be intermitently not fully closing and 'letting by' because very occasionaly water has overheated to extreme temperature. Its happened twice now in last 6 months. I have an old spare solenoid which I kept when I had it changed, because it was noisy, some 20 years ago (...the replacement was just as noisy.) I suppose I could have that re-fitted or better still if there was was a more 'silent' alternative solenoid with same spec? that would be just the ticket.
I found reference to 'obselete'parts here
https://www.baxiboilerparts.com/content/images/boilerdiagrams/diplomat_20-26_1.2.jpg
Potterton part number 40229201
OBSOLETE Solenoid Valve Kit 1/8in BSP 240v
Found 1 part:
OBSOLETE SOLENOID VALVE KIT 1/8IN BSP 240V
Manufacturer: Potterton
Part GC No.: 358-855
Manufacturer Code: 40229201
Part Type: SOLENOID
Fits Appliance(s) GC No.
DIPLOMAT 30/34 BASIC(SPERRYN)HW&SW - 41-590-20
DIPLOMAT 30/34 SB(SPERRYN) - 41-590-25
DIPLOMAT 35/40 BASIC (SPERRYN) - 41-590-21
DIPLOMAT 35/40 SB (SPERRYN) - 41-590-26
DIPLOMAT 41/48 BASIC (SPERRYN) - 41-590-22
DIPLOMAT 41/48 SB (SPERRYN CONTROL) BOILER - 41-590-27
Yes I might risk getting laughed at and start a thread as you suggested... in a few days when I will have more time to answer responses
Patrick
With regard to your boiler, you are suggesting that the gas solenoid is failing to turn off.
How do you know that is not a thermostat fault?
Regardless you need to add an overheat stat. Any modern boiler would always have one now.
Whilst anything could be happening, it seems very unlikely to me that the solenoid is sticking open. For safety reasons they are designed to be as reliable as possible. Nowadays all gas valves are two stage.
Very simple question, why not replace the boiler with a modern efficient unit?
Tony
How do you know that is not a thermostat fault?
Regardless you need to add an overheat stat. Any modern boiler would always have one now.
Whilst anything could be happening, it seems very unlikely to me that the solenoid is sticking open. For safety reasons they are designed to be as reliable as possible. Nowadays all gas valves are two stage.
Very simple question, why not replace the boiler with a modern efficient unit?
Tony
Last edited:
Sponsored Links