I have the above vehicle with an intermittent problem when the engine has warmed up a bit.
Over the past 3 or 4 weeks the problem appears to be getting worse. I have already replaced the HT leads, spark plugs and air filter without success.
My renault dealership wants £40 for half an hour with one of their technicians to plug the diagnostic box into it - the thing is it will either start and no problem will be apparent or it won't start at all. If it starts then they won't find any problem and I'm £40 down and may just as well drive away.
The problem is at cold start the vehicle starts perfectly on the first turn of the engine and I have no running problems at all. Once it has been driven for half hour or so and I turn it off it won't fire up. The engine turns over fine but just won't kick or splutter at all until it's been left for an hour or so to cool down.
But this problem is intermittent.
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Not sure if the following threads are of any help or not?
www.honestjohn.co.uk/forum/post/index.htm?t=28360&...e
www.honestjohn.co.uk/forum/post/index.htm?t=27323
www.honestjohn.co.uk/forum/post/index.htm?t=24036
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I have read through the postings you gave me the links for and am planning to try to clean the flywheel sensor this morning. My haynes manual gives me a reading of 220ohms, is this a stationary reading or a moving reading from the sensor?
The other links that deal with the coolant temperature sensor confuse me, although I don't doubt the experience that leads you to suggest it. My question is what is the bearing of the coolant temperature to whether the engine fires up or not. The movement of the flywheel I can understand, no movement of the engine - no spark to the plugs.
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If you are reading resistance then it needs to be stationary. I am guessing here but with the engine running you would probably be reading a voltage change and an ac type sine wave.
The coolant temperature sensor will be read by the ecu and the amount of fuel injected will be modified by the value of it. Most manuals I have seen give a cold and hot resistance figure for this sensor. If the sensor has failed and is telling the ecu that the engine is cold, when in fact it is hot, the ecu will arrange for more fuel to be injected than the engine needs. This can lead to flooding and a hot start problem.
Hope this helps.
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I removed and cleaned the flywheel sensor this morning but admit it wasn't what I was expecting. The sensing head looked a little burred but the resistance was spot on the 220 ohm. The plug looked clean but still gave it a spray with solvent cleaner.
I can see what you're saying with the temperature sensor but wouldn't I get some spluttering if the engine was being flooded.
Obviously time will tell if the cleaning has had any effect or whether it's worth changing it or the coolant temperature sensor.
The vehicle is an 8v model.
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I can see what you're saying with the temperature sensor but wouldn't I get some spluttering if the engine was being flooded.
No, upon turning on the ignition the temp sensor would give the ECU a false reading so it would richen the mixture as though the engine were cold.
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First, I admit that I know nowt about Renaults (I avoid them where possible!), but, it is possible that the crankshaft sensor only goes open circuit when it is hot.
Was the sensor hot when you checked it with the Ohmeter?
I would expect a car to attempt to fire even if the coolant temperature circuit were open. It might run like a donkey, but it would fire.
number_cruncher
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I'm taking all your valuable advice on board and believe it would be cost effective to change both the sensors mentioned if the cleaning hasn't solved the starting problem but one other thing bugs me.
Surely if these sensors are breaking down when hot the engine management system must be taking information from them all the time and not just when the engine is started.
If the coolant temperature sensor was giving readings back for a cold engine despite it being hot would I not notice it in the fuel consumption, 41mpg on a good run, or very rough engine running or high tick over.
If the flywheel sensor was breaking down when hot would the engine management system not shut the engine down due to it not seeing the engine moving.
The engine was cold when I tested it yesterday with my meter.
Thank-you for all the help
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Wife's got a '98 Clio 1.6 RXE 8v, great car, had a problem where it would not idle when hot, faulty sensor on the throttle body diagnosed, potentially rather expensive, though cured by using better quality fuel, basically wife switched from Tesco to BP when we moved house, problem disappeared shortly afterwards.
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This really does sound like the crank sensors ("flywheel sensor") to me.
The output from this sensor (its a 'variable reluctance' sensor) is proportional to the rate of 'flux cutting' - i.e. its output rises with engine speed. The sensor is giving trouble when its warm. If the engine is running there is enough signal to trigger the ECU. If you stop the engine though, and then crank it over, there is insufficient output at cranking speed to trigger the ECU and the engine therefore doesn't start.
I would also change the coolant sensor because I've heard these are troublesome.
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Hi,
My niece had an almost identical problem and we were told the crank sensors were prone to trouble. I did what you did and even made sure the multiplug terminals were making good contact. Eventually we changed the sensor and it's been fine ever since. For what it costs just replace it.
Hope this helps
--
These are the views of Robin the Technician with 35 years in the trade. I fix, therefore I am...
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