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Discussion Starter #1
Hi All,

Got a 1998 Clio II, 1.2. When ignition turned on the dashboard lights come on as normal and go off as usual. However when I try to start it -nothing (apart from the sound of the fuel pump priming).

Thought it was the starter, so replaced it. Still no joy. Tested it with jump cables of my Safrane's battery and off it went, which made me think there was a problem with the earth lead. So used a jump lead to earth the engine block, and the engine started. Problem is that when I apply throttle the RPM increases and stays there and from the smell of the exhaust its running rich!!

Anyone out there technically minded who can advise me. I'm thinking its probably an expensive ECU problem, but would like to think it might be something simpler.

Would appreciate any thoughts, help or advice. If its an ECU then I think it will be the great scrap yard in the sky for this one.
 

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Hello and welcome to the forum.:)

Have you had the battery tested at all?.If not,that would be the place to start.

If all's well with that,then trace the earth connections from the battery to the engine and make sure they are all clean.

From the way you describe it,it sounds like either the battery is past it's sell by date or there is a corroded earth connection somewhere which has upset the ECU.Remedy the fault,and the ECU should be back to it's full health.ECU's can be sensitive to voltage drop and can do all manner of strange things under these circumsatances.In some cases the ECU earths via the engine,so if the engine isn't earthed properly,this can cause the same faults.
 

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Discussion Starter #4
Hi Guys,

Many thanks for the quick responses.

The battery is new, but I also tried it with my Safrane battery which is new and fully charged. Nothing unless I use the jumper cable to the engine block.

What puzzles me is I can't find any earth connection between the chassis and the engine block. When I checked my wife's megane coupe there is a plastic coated braided wire earthing lead coming off the chassis to the block, so I kinda expected to find the same on the Clio, but no sign of one anywhere, or of there ever having been one.

I put a continuity meter on it and it shows a connection between the chassis and block, but clearly there is a lot of resistance there, which explains why the jumper cable makes the difference. I've replaced the earth lead from the battery and cleaned the chassis connection down to shiny metal, as well as the battery terminal.

I don't have the first idea how the ECU/Immobiliser on these things work, but I wondered if the earth was somehow controlled by the immobiliser, so if immobilised the earth connection is disabled, and if not by the immobiliser, by the ECU. Having said that, it would be a pretty lousy system which could be so easily bypassed by something as simple as jumper cable.

My other and last thought on it, is that when I started the car with the jumper cable earthing the engine block the throttle misbehaved, and I wondered if that indicated a fault with the ECU, or that by using the jumper I had somehow isolated the ECU. (Oh for the days of a normally aspirated engine, with an ignition coil and NO computer).

Obviously, I have been disconnecting and reconnecting the battery more than a few times whilst working on the car, so possibly that has effected it?

Anyway, thanks again for the suggestions and help.

Boeingpete
 

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Looking at my '94 Clio I can't see an earth between engine and body either so I guess it's normal. I had similar problems with the screw type battery connector, and where the earth from the battery connects to the bodywork, ncle cleaned and tightened all ok.

Last thought. Check the connectors on the starter, I had problems once and the connectors were loose / dirty. A quick clean and refit did the trick. If yours is like mine it's tucked behind the engine.
 

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Discussion Starter #6
Hi Chris M,

Thanks for checking your own car, but have cleaned battery and chassis terminals, and even bypassed with jumper cable, still no go. As for starter, fitted it myself, and fires up no problem when the engine block is earthed.

Its all very strange, and I'm now at a complete loss as what to do. Although the car is is great shape otherwise (I've spent a fair bit on it over the years) I'd rather scrap it than spend £450 on a new ECU. Its turning into a money pit.

Thanks again. As and when I get an answer/solution I'll post it here, as I ssupect its a common problem.

Cheers,

Boeingpete
 

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you could try fitting another earth strap from engine to chasis see if that gives a complete cure hav had to do this on a car cannot remember which one.
tinker2
 

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Discussion Starter #8
Hi Tinker2,

Thanks, but as I mentioned in my earlier post, when I do that the RPM accelerate but don't come down when my foot comes off the gas, even though the throttle has closed, which is what makes me think the ECU is cream crackered.

Thanks for the suggestion all the same.
 

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You need to sort out the earthing problem primarily,as it could the cause of the apparent ECU fault.If the engine isn't earthed properly,then the engine sensors won't be working properly and this will cause the ECU to appear to be faulty when really it's reacting to the incorrect information it's getting.

Even a small resistance in the earth system can cause mayhem,so I'd get this sorted first and go from there.:)
 

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Discussion Starter #10
Hi Lagdti,

Just been out with the jumper cable again, earthing the block directly to the battery, and while the car starts the RPM just slowly creeps up, and I have to switch off the ignition. Had hoped I might be able to get it going well enough to be able to drive it to the garage, but not going to happen. Spoke to a mechanic over the phone who says that the bloke must be earthed and that if the ECU was not working it simply wouldn't start. So don't know whats going on with it now.
 

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Hello, joined yesterday, some great technical advice btw, unlike some other forums.:)
I am having the same problem with my girlfriends Clio 1.2
The has ran sweet for almost twelve months until two days ago.
The starter motor had gone and would not turn, just a clicking sound, replaced the starter motor but then nothing not even a click, so after reading many posts on hear i cleaned the TDC sensor, still no luck, so i have tried what this guy has tried and earthed the block with a jump cable, the car fierd up but went straight round to 3000 rpm and stayed there.
Thinking it was and earth issue, i cleaned all the earth connections and battery terminals, still wont start unless the block is earthed via jump cable?
Did you manage to find the cause of the problem?
Any help appreciated
 

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Hi Donny - there are a number of earth connections to the block - there should be one fairly heavy cable running from the engine to the bodywork. Check it is clean and tight.:)
 

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Although i have just thought, there is still the question of why the engine is revving at 3000 rpm when the engine is started?
But will try the earth lead to the block first.
 

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Yeh Dony there are quite a number of sensors on the engine which rely on having a good earth - it's the only way they can make a proper electrical circuit - think about it. As far as I know the fuel pump relay is one of them - never mind the various temperature sensors:)
 

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Cheers for all your help guys, ive managed to sort it out.
After failing to find the earth cable that connects the block to the chassis, i decided to make my own from some thick electrical wire and wired the block to the chassis.
Car fierd up but still revved at 3000rpm, next i removed the throttle body cleaned it aswell as all electrical connectors and ICV.
Now fires up first time every time and idle speed is now around 800rpm.:)
Once again thanks for the help.
:)
 

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Well done Donny - what thickness of cable did you use - remember it may need to carry up to 50 amps plus especially when the starter is fired up - poor earth supply can lead to a starter geting overloaded and burning out - most decent motor factors sell heavy duty earth cables of varying length and the longer the cable - the thicker it needs to be.:)
 

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Yes the cable is quite thick, its as thick as the one from the negative terminal of the battery.
I have a huge reel of 3 core industrial cable in the garage, stripped it down and used one of the cores.
But thanks for the advice, much appreciated.
:d
 

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Discussion Starter #20 (Edited)
Hi Guys,

Don't want to be a wet blanket here but though I was able to start my Clio with the jump lead, there was no sign of the car ever having been fitted with an earth lead from chassis/battery to block. Obviously there is a means by which this is achieved, but by bypassing it permanently it may be causing damage elsewhere, i.e. the CAT, if the fuel control is not being properly metered.

I have booked my car in for a diagnostic with a local garage (not Renaults) and will let you know what it turns up. But I would strongly advise against a quick fix, given how expensive Renault can be for parts.

Incidentally, Donnyshep, after cleaning the throttle control unit, did you try starting it without the additional earth. Just wondering if it could have been the throttle control that was causing the problem all along?
 
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