Motor sounds like crap with cold start on | FerrariChat

Motor sounds like crap with cold start on

Discussion in 'Mondial' started by Russ Gould, Apr 12, 2014.

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  1. Russ Gould

    Russ Gould Formula 3
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    Nov 8, 2004
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    #1 Russ Gould, Apr 12, 2014
    Last edited: Apr 12, 2014
    My engine runs/idles beautifully when warm but of late, for the first cold run (with the cold start engaged) it's rough and sounds like someone tapping on a piece of sheet metal with a hammer. I found one of my header tank mounts gave up allowing the header tank to rub on the air pump pulley. But I don't think this is the source of the noise, as it would be the same at temp. Any ideas? It's an 82 Mondial 8 Coupe
     
  2. 365boxer

    365boxer Formula Junior

    Sep 30, 2004
    389
    La Drova, Spain
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    Nick
    Hi. It's static discharge from the belts. Quite normal and as you say quite loud.
     
  3. ME308

    ME308 Formula 3

    Nov 5, 2003
    1,542
    Munich, Germany
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    Michael
    take some silicon spray and spray continously on to the ac belt/pulley while the engine is running

    you will most probably hear the noise vanishing quickly ;)
    usually your good to go for a couple of starts and if your lucky the noise won`t return for a while
     
  4. peterdavid911

    peterdavid911 Formula 3

    Apr 9, 2012
    1,339
    London, UK
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    Peter
    Hi, mine does exactly the same and was told its very normal. It's the a.c. belts slapping when they're cold.

    Nothing to worry about. It's worse in the winter and the noise goes after a few minutes.
     
  5. ronfrohock

    ronfrohock F1 Rookie
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    Does anyone know of a permanent solution?
     
  6. MvT

    MvT F1 Rookie

    May 25, 2013
    4,248
    The Netherlands - NH
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    Tijn
    I have a new AC belt and the sound is gone. :) Not surel if it is a old rubber thing/behavior or the right tension on the belt. Now I had this sound and when I get a car I replace all the belts and notice it was gone. It is not as easy to replace as the waterpump belt I need to say.
     
  7. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,039
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    About the most you can do (besides installing a fresh belt and using a belt dressing occasionally) is to:

    1. ensure that the AC idler pulley V-groove is coplanar with the "average" plane formed by the crankshaft pulley V-groove and the AC clutch pulley V-groove (a sign that things aren't good here would be unequal wear on the two sides of the AC idler pulley V-groove), and

    2. move the AC compressor axis as close as possible to the crankshaft axis -- this increases the belt wrap angle around the AC idler pulley and helps prevent the V-belt riding up one side of the V-groove and then "snapping" back down into place.

    Are you having the problem even with a fresh belt that is properly tensioned?

    Does spraying a little V-belt dressing on the AC V-belt give you instant temporary relief?
     
  8. ronfrohock

    ronfrohock F1 Rookie
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    Steve,
    I have had new belts installed and properly tensioned and pulleys aligned. This solved the problem for a while but it always comes back with time.
    I have been hesitant to use dressing. Maybe I shouldn't be....
    I understand its a nuisance and not harmful but I sure would like to find a permeant solution.
     
  9. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
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    Steve Magnusson
    Then you are left with doing something to increase the belt wrap angle on the idler pulley or using a belt dressing. You can't use a belt dressing daily, but once every 3-6 months wouldn't be crazy IMO.
     
  10. ronfrohock

    ronfrohock F1 Rookie
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    Thanks Steve,
    As always, I truly appreciate your advise. I will get a can.
     
  11. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    Jan 11, 2001
    25,039
    30°30'40" N 97°35'41" W (Texas)
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    Steve Magnusson
    I've liked using the Permatex brand (which I think you can find in an inexpensive, small 5oz spray can size for a test) -- but please post your result if you try something (regardless of brand).
     
  12. Russ Gould

    Russ Gould Formula 3
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    Nov 8, 2004
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    Well it's not the belts, it's just very rough idle, engine bucking and farting. When I bypass the temp switch on the header tank (effectively disabling cold start) it smooths right out albeit at 900 rpm. Separately, when I disconnect the wires to the auxiliary fuel line on the plenum (blue thingie) it makes no difference. So while I have solved the problem (didn't like cold start anyway) I still don't know what was causing the rough idle. Something in the cold idle mechanism is not working as it should ... maybe it's getting the extra air but not getting the extra rich fuel? Or getting too much fuel and not enough air (doesn't smell rich).
     
  13. Russ Gould

    Russ Gould Formula 3
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    Nov 8, 2004
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    Well I checked the function of the thermo-time switch by measuring cold resistance from plenum electrovalve connector plug to ground, and I do get a very low (one ohm) resistance on one of the connectors with the cold motor. In other words, the circuit that operates the aux fuel electrovalve is grounded when the motor is cold, so the valve should be getting current while the motor is cold. That doesn't mean it's letting fuel through though. But in any case, as I understand it this extra fuel is only injected (81 model year) while the starter is cranking, so it can't be the cause of rough idle for the duration of the cold start circuit being active.

    Since the only other function of the cold start system is to admit extra air into the plenum via the aux air valve, and that is clearly doing something for the duration of cold start (and all it can do is open), I am flummoxed.
     
  14. moysiuan

    moysiuan F1 Rookie
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    How did this get resolved, sounds like my issue.
     
  15. Russ Gould

    Russ Gould Formula 3
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    I disabled the cold start, something that is advisable anyway unless you drive in winter and live in the northern states. Still don't know why the cold start was causing the engine to run so roughly. I no longer own the car ...
     
  16. moysiuan

    moysiuan F1 Rookie
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    Thank you for the update.
     

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