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Discussion Starter #1
Over the last few days my Megane has been starting very poorly, turning over over for sometime and struggling to start. It would eventually start and then once warm drove fine. I went to start it this morning and this time it turned over but wouldn't start. I have given the crankshaft sensor a clean, but no change. Also checked for codes and nothing.
Any ideas where to look next?

Cheers
Johnny
 

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Super Moderator Technical Supremo Platinum Member
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Cold mornings?
My suspicion would be coolant temp sensor, equivalent of no choke (or not enough)
A guess but relatively cheap and easy to swap to eliminate.
 

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Very cheap indeed, can be had for a tenner, so worth a try.

A failing coil pack, on this engine, can cause "cold" issues. Worth testing. Additionally, do you hear the fuel pump fire up when the ignition is on?
 

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Temp sensor, as said above. Coil pack is worth checking. Do you hear the pump prime when ignition is on?

An old battery can cause failure to start, or long crank cycles prior to an engine starting, even if it holds a healthy charge. I had this issue.
 

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Discussion Starter #6
Would a coolant temp sensor stop it from starting? Wouldn't it just splutter as if it's not getting enough fuel but sound like it's trying? Sorry grew up on aircooled VW engines, all these sensors spin my head!
 

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Usually a temp sensor causes rough running. Have you checked the coil pack? Checked all cables and terminals for breaks, loose connections or corrosion?

I understand you believe the pump is OK, but can you hear it engage the instant you turn ignition on?

Not so easy to check, but cambelt might be slipping. If timing is out enough, you'll have failure to start. Slipping can account for rough running prior to your failure to start. Not likely, so put at bottom of list for now, and test the more common things.
 

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Coolant sensor causing it not to start??
Simplistic explanation.
With carburetor cars, with petrol lawnmowers, hedge trimmers, first thing you do when starting is pull the choke out.
Don't do that and you can crank forever and they will not fire.
With cars, the cold start system has become more and more automated.
With carbs, auto chokes were developed. And often failed, anyone who had one that did will know that the thing would not fire when cold.
The modern equivalent is the coolant temp sensor.
It tells the ECU how cold or hot the engine is and the ECU uses that information to decide whether some "choke" is needed, not the butterfly in the carb anymore but adjustments to the mixture so the beasty fires.
Coolant temp sensors can fail in different ways and some will certainly allow starting but then cause rough running due to overfueling.
If one fails in a way that says the engine is warm enough for a lean mixture when the engine wants a rich one, bad start or no start.
If it does start, as the engine warms up, the lean mixture is actually what the engine wants so it runs smoothly.

As I said, a guess but one that has some basis and is cheap enough to throw parts darts at.
And as Brendan has pointed out, could be other things but at least one option will be crossed of the list
 

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take spark plugs out dry/clean or change them.
 

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Discussion Starter #10
Working my way through the list. Crank sensor cleaned, replacement coolant temp sensor put in. Fan comes on if not connected and then goes off as soon as its connected (with key in slot). I can hear a high pitched noise when the ignition is on which I'm guessing is the fuel pump.
Thought that I would take a quick look at the coil packs and the left hand one had oil on the bottom. Oil looked super clean so was obviously over spill from filling up. Other 3 are dry.
May just replace coil packs and spark plugs and see where we are at.
 

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Pull the plug on the dephaser solenoid next to the oil filler cap .................... starting now?

The high pitched noise with ignition on under the bonnet is the throttle body's stepper motor constantly adjusting the throttle - even if you dont touch the throttle pedal. Its always there and is nothing to worry about.

The fuel pump (in tank) runs at most for a few seconds if the engine is not running
 

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Still not firing?
Confirm immobiliser light doing what it should please.
I don't think it is that but would kick myself if didn't ask and it was
 

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Discussion Starter #14
Pulled dephaser out and no wouldn't start. Did come up with injector fault on the dash. Will need to put battery on charge as now running low, will re check the fuel pump. Whats the best way to do this?
 

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Pulled dephaser out and no wouldn't start. Did come up with injector fault on the dash. Will need to put battery on charge as now running low, will re check the fuel pump. Whats the best way to do this?
OK - quite normal that dash moan ................... its "injection" and not "injector" yes?

Check fuel pump operation - plumb a T-piece into the line coming from the pump to the fuel rail - you should be seeing around 2.5 to 3 Bar there soon after ignition is switched on - and if you switch off the ignition you should continue to see around that much for quite a few 10s of seconds if all is well.

You are not perhaps smelling a lot of fuel from the exhaust?

Battery flat in itself can cause untold miseries.....................

Remove negative terminal from battery ............... put charger on battery and allow to fully charge ............... switch on headlights with ignition off, NOW connect negative terminal of battery and tighten - switch off headlights - switch on ignition (dont start engine) and leave it sitting like that for a minute without touching throttle pedal ................. NOW try to start engine............

In theory you should have no engine related complaints on the dash now

Everything else works as it should.
Erm no :p .............. at least one item is not playing ball
 

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It is still not clear if you can hear the pump? It should activate for 2 seconds as soon as you put the key in. Noise comes from the rear.
 

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Discussion Starter #19
Ok. So swapped out the coolant sensor. Coolant went everywhere! But working. Have replaced the spark plugs (1 was covered in oil from overspill when filling) and coil packs and it started straight away. Only issue was a big plume of white smoke coming from the rear (I was sitting in the drivers seat so guessing from the exhaust). I turned the motor off in case something wasn't right. What could have caused this? It didn't smell like burning oil, in fact wasn't smelly really. Could this have built up from sitting there for the last 10 days or could it be linked to the coolant spillage?
 

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White with little smell could simply be condensation.
Could be oil from the overspill got into the one cylinder.
Can't see it being coolant (next time, seal the expansion bottle with a bit of plastic bag and screw the cap back on) unless some spilt on exhaust and the plume was being carried under the car... has a distinctive smell though.
Have you tried it again?
 
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