Coil problem (not the normal one) laguna 2 V6
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  1. #1
    Tadpole
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    Default Coil problem (not the normal one) laguna 2 V6

    Hi all , I have a non functional cylinder #2 on my 2002 laguna v6. I have worked out (as have a couple of renault shops) that the issue is not the coil or the spark plug so assuming I'm left with an ECU or wiring fault somewhere.

    I'm in the process of unwrapping and following the 2 x cables from the coil to....?
    My assumption is that 1 wire goes to a power source? and the other to the ECU (under the battery)?

    Could someone help guide me to effectively testing the 2 wires at the coil plug to determine which wire is which? I have a multimeter but unsure what I should be seeing to confirm OK or not.

    Has anyone else come across a similar issue?

    Also need to confirm the following;
    - If there is a fault with the coil, does the ECU shut this cylinder down until fault cleared (meaning I'm not going to know if I do find the issue?)
    - If it is something in the ECU, can they be swapped for one removed from another car? or can they be repaired?

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    Bit stuck on this, happy to do the labour intensive investigation work but need to rule out the easy stuff first.

    Any help as always really appreciated.

  2. #2
    1000+ Posts robmac's Avatar
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    Can't you unplug the ECU and tackle the fault with an ohm meter?

    Before doing anything major I would unplug and re-plug all wiring involved with coil circuits.

    Cutting the loom open sounds very drastic fault finding.

    You do need a decent wiring diagram before you start 'tho.

    EDIT: Some ECUs use an external transistor (pack?) to trigger the coils so you may look there. I believe a wiring diagram and connector legend is the first step.

  3. #3
    Tadpole
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    Hi Robmac, mate I'm too familiar with multimeters and testing. Assume ohms is measuring quality of the wires or similar. What should I be looking at, do I just put probes on each end of each wire?

    By cutting the loom open I mean unwrapping the screeds of insulation tape to see if there are any breaks etc.

    I have been trying to source workshop manuals re wiring diagrams but not having much luck. Well nothing specific to engine bay wiring anyway. Can you recommend anything?

    Cheers

  4. #4
    Fellow Frogger!
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    You would need a wiring diagram to know where to check from/to.
    Unwrapping looms looking for breaks (without measuring) could waste a lot of time, as the conductor may be broken inside the insulation.

    I read this recently (re the Laguna V6 no spark at a coil):
    Check the engine-flywheel target (warpage or formation of cracks).
    Repair if necessary.


    It appears that the coils are triggered via 6 points on the flywheel.
    Maybe look into that first?

    Cheers
    spiz

  5. #5
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by joshnzl View Post
    Hi Robmac, mate I'm too familiar with multimeters and testing. Assume ohms is measuring quality of the wires or similar. What should I be looking at, do I just put probes on each end of each wire?

    By cutting the loom open I mean unwrapping the screeds of insulation tape to see if there are any breaks etc.

    I have been trying to source workshop manuals re wiring diagrams but not having much luck. Well nothing specific to engine bay wiring anyway. Can you recommend anything?

    Cheers
    Yes an "ohm meter" is meter in series with a battery and a few resistors in concept.

    The reading on the meter is a measurement of the resistance between the meter probes. Low resistance is good. The restance of wires from the ECU to the coils should be low, a few ohms or less.

    Ohms is the unit of resistance measurement is the ratio voltage divided by current (amps).

    Read up on some basic electronic courses on the net. An ohm meter/ multimeter is a very useful too.


    CALLING RENAULT LAG OWNERS WE NEED A WIRING DIAGRAM IN PDF FORMAT PLEASE

  6. #6
    1000+ Posts renault8&10's Avatar
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    Would there not be one on the site bob posted recently (A Czech site I think)?

    I'll look to see if I have a laguna manual but it would be a UK Haynes one and may not be that useful for the V6 diagram.
    KB


  7. #7
    1000+ Posts Fordman's Avatar
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    Quote Originally Posted by Spiz View Post
    I read this recently (re the Laguna V6 no spark at a coil):
    Check the engine-flywheel target (warpage or formation of cracks).
    Repair if necessary.


    It appears that the coils are triggered via 6 points on the flywheel.
    Maybe look into that first?

    Cheers
    I would think this is a very good thing to check. I have only seen single (TDC) sensor operation - if they have 6 (or would it be 3?) pickups it would knock out the one cylinder. Possibly answering my own question there, it would probably knock out 2 cylinders unless they have cleverly devised to pick up every second revolution. Another thought is that with 6 pickups it fires the plug every revolution even if not required - this has been the case on other engines (First V6 Commodores were one).

    Definitely worth looking into.
    2004 Scenic I 2.0 auto (Hers)
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  8. #8
    Tadpole
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    Just an update, have checked all the wiring and seems to be ok. Zero resistance from cable going to ECU and volts match what is going to the other 'working coils'.

    Will start to investigate what is creating spark from the firewall (thanks spiz and fordman). If anyone can help with what these sensors look like and where they are located that would be great. Otherwise will start searching the Internet. Does anyone know if Haynes actually did a manual for the Laguna 2 v6?

    Will keep you posted

  9. #9
    1000+ Posts renault8&10's Avatar
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    I did have a look at the Manual I have (Haynes), it only covers the 1.9 diesel and 1.8 petrol motors and the wiring diagrams it does have are less than pathetic. I couldn't find a Haynes manual for the V6 when I went looking previously but I wouldn't discount those online sources Bob quoted on another thread.
    KB


  10. #10
    VIP Sponsor David Cavanagh's Avatar
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    Quote Originally Posted by joshnzl View Post
    Just an update, have checked all the wiring and seems to be ok. Zero resistance from cable going to ECU and volts match what is going to the other 'working coils'.

    Will start to investigate what is creating spark from the firewall (thanks spiz and fordman). If anyone can help with what these sensors look like and where they are located that would be great. Otherwise will start searching the Internet. Does anyone know if Haynes actually did a manual for the Laguna 2 v6?

    Will keep you posted
    I have a factory manual for them. Its about 3 times the thickness of a Haynes manual and it only does the electrics. I think its exactly what you need.
    Your welcome to come look at it, take notes, photocopy but it doesn't leave the building.
    David Cavanagh

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  11. #11
    Tadpole
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    Default not happy

    Hi all, well after many hours of personal investigation I gave up and took to Renault dealer to diagnose. They are confident it is the computer that is causing the issue. Right now they are investigating testing and potentially repairing this computer? Has anyone had or done this in Melbourne?

    2nd option is investigating replacing with a 2nd hand unit. Has anyone gone down this track and know whats involved i.e. replacing card readers and other computers as well as reprogramming to car? Is this feasible or possible.

    3rd and final option is either replacing with new one quoted $2600 plus programming!!! or regretfully passing an 80,000km car in otherwise great condition to the wreckers and investing in something else.

    Anyone with any suggestions/help?
    Josh
    Last edited by joshnzl; 1st August 2012 at 05:24 PM.

  12. #12
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by Fordman View Post
    Another thought is that with 6 pickups it fires the plug every revolution even if not required - this has been the case on other engines (First V6 Commodores were one).

    Definitely worth looking into.
    So if its a wasted spark arrangement can you just bum a ride off the paired cylinder's signal ??


    Jo

  13. #13
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by jo proffi View Post
    So if its a wasted spark arrangement can you just bum a ride off the paired cylinder's signal ??


    Jo
    The output Zistor might not like it

  14. #14
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by robmac View Post
    The output Zistor might not like it
    Rob, I'm sure some one like you with trickery knowledge could make up some gizmo.

    Jo

  15. #15
    1000+ Posts robmac's Avatar
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    Quote Originally Posted by jo proffi View Post
    Rob, I'm sure some one like you with trickery knowledge could make up some gizmo.

    Jo
    Jo,

    I probably could but whether others can follow the how-to instructions, I'm not sure.

    I posted the Estima remote hack (on another forum), documented enough for anyone suitably capable to make it. I even gave the arduino micro source code.

    So far I've got dozens of PMs asking questions which indicate the senders haven't got a clue.

    In, fact I'm thinking of deleting the post

    So I'm going to be careful of detailed "technical" advice in future.

    I'd fix the output transistor in the ECU anyway. Doing anything else is trap for others later on.

    cheers

    Rob

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