Cx aei
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Thread: Cx aei

  1. #1
    Tadpole
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    Default Cx aei

    Hi everybody,

    I've got four CXes here in UK (3x T2S2 + 1x GTi).

    I got the latest T2S2 a week ago but it is throwing a fit like I've not seen before with any of my previous CXes. It only starts after a lot of coaxing & then runs on only 2 or 3 cylinders. It was also just a bit flooded last week (which might be related to the fault or possibly, just the excessive attempts to start it) - fuel dripping from inlet by throttle & intercooler just a little bit full of petrol (glad that lot was spotted before it blew me up!)

    I've owned CX for around 30 years so I've done the obvious:-
    - checked for fuel & sparks
    - tested coils & capacitors
    - checked wiring integrity to injectors
    - replaced crank-sensor (mine has only one)
    - replaced Big Blue
    - pulled apart every connector in sight, cleaned & re-seated
    - polished the earth stud by the battery
    - measured continuity of connections through wiring loom wherever I can
    - used every swear word I know

    But the thing is still being very stubborn so tomorrow, I'm going to swap out the MAF sensor & the AEI.

    Here's the question - is it possible to disconnect the connectors to the AEI (LH wing by battery) without first having to unbolt the unit? (Problem is that the wire clips on the connectors are underneath..?) I'm rather hoping I don't have to disassemble the contents of the wing just to perform a five second yes/no test on one box...

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    As for the air-intake/MAF, I think I've just got to unbolt the whole lot but fortunately, there isn't much in the way on that side of the car. And yes, it'll inevitably be the last thing I look at so the MAF but if I do things the other way around, it'll be the AEI...

    With thanks.
    Last edited by eddief; 11th December 2018 at 01:45 PM. Reason: typo

  2. #2
    Real cars have hydraulics DoubleChevron's Avatar
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    Default

    check the fuel pressure regulator. I'm also betting you have dodgy connectors onto one of the coils. Running on 2 cylinders will always be a coil .... Generally wiggling the wiring connector will bring the cylinders back to life temporarily (until you fix the wiring connectors)

    The only way I can think fuel would get into the inlet tract down near the intercooler is if the cold start injector was leaking/spraying. However I'm pretty sure a Turbo II doesn't have a cold start injector (only turbo 1's had them).
    'Cit' homepage:
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  3. #3
    Tadpole
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    Thanks for the quick reply - much appreciated.

    You are correct (no cold-start injector on this one) but I'm still not completely happy about all the fuel that collected on the intake side because it shouldn't be possible to get fuel any further back in the system than the cylinders (I'll do a quick compression test just to check I haven't got a stuck inlet valve).

    And I'll certainly double/triple-check the coil wiring plus the pressure regulator (mainly, because that's a lot easier than messing with the AEI & MAF!)

    Thanks again.

  4. #4
    Tadpole
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    A quick update... Tested for sparks (again) but this time around, #3 wasn't sparking even though #2 was. Since they form a series circuit (via the coil) that should not be possible - the circuit is earth-plug-lead-coil-lead-plug-earth; break that at any point & it should stop working completely - not just for one plug. Swapped plugs & leads - same result.

    The only conclusion I could reach was that the secondary side of the coil has to be shorting to earth (although continuity test of secondary to case showed the expected open circuit). It's probably insulation breaking down at high voltages?

    Anyway, a new set of coils is now on its way from CX-Basis (unfortunately, the spares I have all have a different connector for the primary side).

  5. #5
    Fellow Frogger! marc61's Avatar
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    If the car hasn’t been used for a long while and the fuel is old, ignition can be plain difficult with modern fuels and old plugs. New plugs are worth fitting. Then don’t let it idle for too long without putting it under load and going for a drive.
    JohnW likes this.
    Cheers, Marc.

    1987 CX GTi T2 Maikonics
    1972 SM 2.7 carb
    1972 DS21 EFI

  6. #6
    Tadpole
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    Thanks marc61 but I've already headed that one off - almost all of the fuel is new (as are the plugs). I'm 99% confident that the misfire is down to the #2/#3 coil failing internally. Hopefully, the new coil will fix this snag (although there may be more lurking of course) & I'll then be able to focus on getting it ready for the road.

  7. #7
    Too many posts! JohnW's Avatar
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    Guildford eh? I was born there!

    Good luck with the nonsense problem. These things are sent to try us.

    Cheers
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  8. #8
    Tadpole
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    Hi JohnW - actually Cranleigh (but nobody outside of Surrey knows where that is!) Can't wait for those coils to arrive so I can get the beast firing on all cylinders again..!

  9. #9
    Too many posts! JohnW's Avatar
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    Cranleigh is where my parents lived!! Small world. I lived there too, until I was 2 anyway.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  10. #10
    Tadpole
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    Reckon I might have figured out how petrol has been getting into the intake manifold & intercooler. If the diaphragm in the pressure regulator had perished then that would allow (pressurised) petrol straight into these areas via the vacuum pipes. I will test this theory & let you all know the results (assuming I don't blow myself up in the process...)

  11. #11
    Tadpole
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    Uncanny that DoubleChevron's original advice has ended up being exactly where I seem to be at this moment (coils & fuel regulator) - hats off to you sir! Just a bit annoyed that the courier didn't bother delivering my coils on Friday (when it gets busy around Xmas, they have a habit of skipping the more remote addresses to stay on schedule...) Hopefully, I'll be able to move things forward early next week.

  12. #12
    Fellow Frogger
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    Yes, the vacuum pipe on a failing regulator or damper can draw a fair bit of fuel into the manifold, yet still work well enough for the engine to run OK. I had that problem with an XM and it was hard to start and smoked a lot on startup. Different system, but same idea. If that is a problem it should be obviously wet after a little cranking. It should be easy to test it with compressed air or by substitution in your case.

    If your oil level has risen obviously, change the oil as it is likely to have been topped up with raw fuel. That's always a risk with a non-starter, but it also happened on a C5 V6 with a blocked catalyst.

    What is the state of the battery and alternator? CX electricals can be quite marginal and a failing battery can see electronic injectors randomly deciding not to inject etc.. A battery can seem OK with a multimeter, but in fact only have a very weak surface charge.

    30+ yo AEI is probably now well beyond the design life of many of the components used to make it.

  13. #13
    Too many posts! JohnW's Avatar
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    Quote Originally Posted by eddief View Post
    Uncanny that DoubleChevron's original advice has ended up being exactly where I seem to be at this moment (coils & fuel regulator) - hats off to you sir! Just a bit annoyed that the courier didn't bother delivering my coils on Friday (when it gets busy around Xmas, they have a habit of skipping the more remote addresses to stay on schedule...) Hopefully, I'll be able to move things forward early next week.
    Not uncanny really. He has huge experience with these cars.
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Renault Scenic 2006 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

  14. #14
    Tadpole
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    And the car lives!

    Main fault was a failed fuel-pressure regulator that was leaking (injecting!) fuel directly into the intake via the vacuum hoses.

    Secondary fault was a dodgy coil (which only failed occasionally).

    The beast is now tucked away in the barn with her three sisters.

    Thanks to everybody who chipped in with advice - much appreciated!

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