Non Start

Evening All

Just wanting to pick some brains really, Ive got a 98 v70r auto which this morning decided not to start.

Drove the car last night fine and went to its this morning and it just cranks and cranks. I noticed as soon as the ignition is put on the rad fan kicks in. Left the car for a couple of hours and tried again still the same. Rad fan kicks in, car cranks but doesnt start.

Came home from work with 2 code reader and some tools to check spark and fuel, but no faults stored in the ecu and now the car starts! fan doesnt kick in untill upto to temp but i cant get my head round what happened. Any suggestions or thought would be great as i have 2 small children and dont want to get caught out

Thanks in advance

Has the ecu in it been remapped?

Only reason I ask is when remapping mine, there was an issue with the chip not connecting properly inside the ecu which caused the rad fan to kick in when turning the ignition on.

Hi Dave thanks for the reply, not that i know of but with the fan comming on it would seem like its in fail safe mode

Another item could be the engine temperature sensor. If it was intermittently faulty and falsely showing a high engine temp it may be possible the ecu would start the fan immediately upon the ignition stage. The only thing with this is i'm not sure a false high engine temp (or hot start) would be enough to reduce the fuelling amount to not be able to start the engine.

Thanks again dave yeah that was my initial thought but like you say couldnt see why it would stop the car starting! Just started it again and runs but sounds like its going to cut out, ive noticed the service light is on, can i confirm this is just a service light and not a engine warning light like some renaults have

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Originally Posted by Dangerous Dave

Another item could be the engine temperature sensor. If it was intermittently faulty and falsely showing a high engine temp it may be possible the ecu would start the fan immediately upon the ignition stage. The only thing with this is i'm not sure a false high engine temp (or hot start) would be enough to reduce the fuelling amount to not be able to start the engine.

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Most Engine Temp. sensors 'fail safe' to a negative reading, ie,-40*C. This is if the sensor is open circuit. In these conditions, the ECU may be mapped to put the Rad fans on as a form of self preservation and protection. Citroen and Peugeots all do it!

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Originally Posted by Robbin Houses

Thanks again dave yeah that was my initial thought but like you say couldn't see why it would stop the car starting! Just started it again and runs but sounds like its going to cut out, i've noticed the service light is on, can i confirm this is just a service light and not a engine warning light like some renaults have

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Then you have either an ignition fault, ie Crank shaft sensor or a fuel pressure sensor / Regulator fault.

On a P1 V70, the service light is exactly that....an orange light with SERV in it. It does not mean the same as what Renaults do and is not a Engine light, as per some Renaults and Vauxhalls.


To diagnose a crank sensor you need 'live readings' or a fault code. Crank sensors, generally, give up when they are hot and build up static.
The good news is, if it IS the crank sensor, you'll know because you won't have switching at the injectors nor will you have a spark! SO, NO spark and NO switching but 12v and 5v present at the MAF normally means...Dead Crank sensor.

Quote:

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Originally Posted by LeeT5

Most Engine Temp. sensors 'fail safe' to a negative reading, ie,-40*C. This is if the sensor is open circuit. In these conditions, the ECU may be mapped to put the Rad fans on as a form of self preservation and protection. Citroen and Peugeots all do it!

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My inlet temp sensor is currently not connected (wires have snapped off at the connector) and using the Torque app it shows -40c. I find it quite interesting that -40c would be a default for 'fail safe' purposes, as to my mind wouldn't it be safer for the engine to assume a 'hot' temp instead? I suppose it depends what it's measuring though. I was pondering this very thing this morning and wondered if - because the ECM is rather clever - it knows that the temp is not actually -40c because a} that's excessively cold and b} it's a constant and consistent reading and so it recognises that it's being fed a duff signal and so defaults to certain fail safe parameters.

From looking at the M4.4 maps it seems the air intake temp only affects the turbo control system, it shouldn't have any effect on fuelling or ignition. Not sure how it affects ME7 variants

Thanks for the replys guys not had a chance to get back on the car l, going to have a tinker tomorrow and ill report back my findings! Thanks again