High idle on 340

Discussion in 'Volvo 340' started by C.M.F., Sep 17, 2005.

  1. C.M.F.

    C.M.F. Guest

    Only when engine is hot, idle up to almost 1000 rpm (very hot) since 400
    when is cold. Why could it is?, Engine is 1.7 with solex carb. Trothle is
    adjust at min.

    How can I adjust mixture?

    thanks
     
    C.M.F., Sep 17, 2005
    #1
  2. Warped base of carb. I'll put money (and lots of it) on that being your
    problem.

    Tim..
     
    Tim \(remove obvious\), Sep 17, 2005
    #2
  3. C.M.F.

    C.M.F. Guest

    I have just tighened screws of the carb to base and it improves. So you are
    right. Thanks.

    What about adjust mixture?
     
    C.M.F., Sep 17, 2005
    #3
  4. C.M.F.

    Andy Guest

    Do NOT overtighten because all you will do is warp the carb base even more
    than it is.

    This is a very common issue with the Solex and Weber carbs, cost cutting by
    Renault is my guess. At the base of the carb is a 1/2 inch thick (or
    thereabouts) gasket that was supposedly designed to get around the carb base
    bowing, it was never particularly successful. This gasket costs something
    stupid like £80 and must be replaced each time the carb is removed.

    If the problem returns (and I hate to be the forbearer of bad tidings) but
    it could well do so then retightening the bolts is likely to make the matter
    worse. You may get away with a replacement gasket, it depends on how badly
    warped the carb base is.

    The carb base is already on the thin side which does not help the bowing
    issue so having the bottom of the base milled is also likely only to be a
    temporary fix (and you will still need a new base gasket.

    Unless someone knows of a fix (PLEASE LET ME KNOW) you mare heading for a
    replacement carb.

    A possible alternative is to get a carb AND inlet manifold TOGETHER from a
    breakers like CP Motors 01827 331 402, NorthWest Motor TRading 01942 322 880
    or Braydon Motors 0208 985 2266, there are probably others but these guys
    specialise in breaking up Volvos (CP Motors I found out recently also do
    servicing). Cricial that the carb and manifold are NOT seperated and then
    all you will need is a manifold to block gasket which will set you back
    around a tenner.

    If you try and seal the carb base with some sort of gunge I was told by a
    Volvo techie that this should be an absolute last resort only job as the
    petrol vapoyr usually breaks down whatever sealer you yse and bits of the
    sealer end up inside the carbs jets.

    We went down the replacement manifold/carb route and with a manifold and
    carb from NWMotor Trading for about £80 all up. It came of a good running
    1.7 but even that is after 4 years presenting the same problem. We have
    come to live with it.

    Andy
     
    Andy, Sep 18, 2005
    #4
  5. Hi all,

    Further to my previous post, and Andy's lengthy reply, it is possible to use
    the carb and manifold from a Renault 1.7 from either the R19 or 21 with some
    modication. You need the 1.7 energy engine though, which has a much better
    twin barrel Weber carb.

    It will need re-routing of vacuum pipes, and some blanking off for it to
    work though, but once fitted and working is warpy-base free.

    Tim..
     
    Tim \(remove obvious\), Sep 18, 2005
    #5
  6. Hi all,

    Further to my previous post, and Andy's lengthy reply, it is possible to use
    the carb and manifold from a Renault 1.7 from either the R19 or 21 with some
    modication. You need the 1.7 energy engine though, which has a much better
    twin barrel Weber carb.

    It will need re-routing of vacuum pipes, and some blanking off for it to
    work though, but once fitted and working is warpy-base free.

    Tim..
     
    Tim \(remove obvious\), Sep 18, 2005
    #6
  7. C.M.F.

    Andy Guest

    We have the Weber carb. Usually Weber are a good name in carbs. The ones
    fitted to the 1.7 volvo/Renaylt engine has this weakness. Pity cos the
    engine (107k miles) goes like a steam train.

    Andy
     
    Andy, Sep 18, 2005
    #7
  8. C.M.F.

    C.M.F. Guest

    Thanks at all for yours advices, they are very interestings and useful.
     
    C.M.F., Sep 18, 2005
    #8
  9. C.M.F.

    Randy G. Guest

    mind you, I have not worked on these specific carbs but do have some
    Solex experience.

    Is it actually a gasket, or is it a hard, lastic spacer. usually the
    "thick" gaskets are a heat speacer made to insulate the carbh from teh
    heat of the intake manifold when the car is turned off after a hot
    drive. If that is the case, I would find some gasket material to make
    gaskets for both sides.

    Another alternative- thoroughly clean the carb base and manifold. Wrap
    the bottom of the carb in some stretchy plastic or shrink wrap and do
    the same on the intake manifold. Use some JB Weld, put a thin coat on
    the gasket and assemble with the least amount of torque possible. Wait
    until it hardens, then disassemble, remove the plastic wrap, and
    reassemble.

    Are there no gas-resistant sealnts? I seem to rmember some epoxy made
    to seal gas tanks and such, or even use something like Kreem or other
    tank liner material to build up a gasket to form fit the warpage.

    Just brainstorming... maybe more the later than the former....


    __ __
    Randy & \ \/ /alerie's
    \__/olvos
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
     
    Randy G., Sep 18, 2005
    #9
  10. C.M.F.

    Pi Guest

    I had an opel kadett long time ago. Wasn't running well. I wanted to
    look in the carb, lifted the airfilter and the whole carb came with
    it! Was standing completely loose!

    Pi
     
    Pi, Sep 19, 2005
    #10
  11. C.M.F.

    Andy Coles Guest

    Storming Brains are good.

    You are probably right about it being a heat insulant (as well) but Volvo
    told me it was there because of the bowing carb base issues. I do not
    actually remember there being a paper thin gasket on each side of the thick
    thingy, there may have been it is just that I can not remember.

    I do remember putting a straight edge across the carb base and noticing it
    bow upwards in the centre. The carb base has 4 fixing bolts (studs/nuts)
    one on each corner and either the base of the carb needed to be thicker ot
    it needed another 2 fixing studs in the middle to help stop the bowing.. It
    seems that the more the 4 corner bolts are tightened the greater the chance
    of the carb base bowing.

    I like the idea of making and trying a thicker paper/thin card gasket and
    fit this between the thick spacer and the carb base, it could just work.
    WHAT DO YOU HAVE TO LOOSE.

    I spoke at length with people about using some form of liquid gasket
    including a techi who builds F1 racing engines and to a core they were NOT
    in favour for bits being effected by the petrol vapour and getting stuck
    somewhere inside the carb/jet etc.

    We also discussed having the carb base skimmed but keeping swarf out of the
    carb was close to an impossibility so would have needed a complete carm
    strip and clean, and for what, at best a temporily flat but even weaker carb
    base.

    Andy
     
    Andy Coles, Sep 27, 2005
    #11
  12. C.M.F.

    Randy G. Guest

    How about this: make a thin metal gasket to match the outside
    perimeter of the carb. Run a thin bead of JB Weld along the base of
    the carb- mostly near the center where it is bowed up, then place the
    carb on the gasket on a sheet of glass so that the JB Weld fills the
    gap between the metal gasket and the base of the carb. In essence, you
    are making a new carb base a few tenths thick, but not making the carb
    any taller than it has to be.
    I agree.



    __ __
    Randy & \ \/ /alerie's
    \__/olvos
    '90 245 Estate - '93 965 Estate
    "Shelby" & "Kate"
     
    Randy G., Sep 27, 2005
    #12
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