504 over revving
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  1. #1
    Tadpole
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    Default 504 over revving

    my 72 504 is rarely used but in pristine condition and generally starts and runs fine
    the last time I went to start it, it immediately started to over rev so I immediately turned it off
    tried again and the same thing happened

    Any ideas of where to start?

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    Gavin

  2. #2
    1000+ Posts jo proffi's Avatar
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    Start with the easy stuff.
    Check the physical parts from the pedal to the throttle, that they are returning and that the throttle is fully closed.
    If thats all good, use your ears and find out where the air is getting in. It is air getting in that is the issue. Sometimes a cracked hose can let in air. Sometimes a backfire can blow off a larger hose and cause these issues.


    Dont be too precious about a few revs at start up when trying to suss out the issue. Assuming it is not screaming up to +5000rpm the motor will cope fine as there is no load on it.


    Jo

  3. #3
    1000+ Posts Beano's Avatar
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    My '72 504 accelerator pedal stuck in the 'down' position once. It was because of the little plastic gate behind the pedal.
    I changed to a later style pedal which hangs down and does not touch the floor at the bottom.

    If by "over rev" you mean quite high, then you can damage the engine. But if you just mean it is revving higher than normal, try (apart from what others suggested) spraying some WD40 on the carby linkages. Use a fair bit.

  4. #4
    Fellow Frogger! julian b's Avatar
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    There should be a bit of slack in the inner cable at the carby when idling. If it is tight there may be something stopping it from returning properly like the outer cable not seated properly .

  5. #5
    1000+ Posts Beano's Avatar
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    Quote Originally Posted by jo proffi View Post
    It is air getting in that is the issue.
    Correct. If it is revving a little high, that is the usual prob.

    For REALLY high revving, a stuck pedal or cable is the most likely problem

  6. #6
    Fellow Frogger!
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    All of the above with a sticking accelerator cable [or a broken one] the prime suspect. When you find it put a second spring onto the accel. linkages on the carby to ensure that the throttle stays off unless pushed. It doesn't have to be a very strong spring to help. Neil

  7. #7
    1000+ Posts bluey504's Avatar
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    Quote Originally Posted by Beano View Post
    Correct. If it is revving a little high, that is the usual prob.

    For REALLY high revving, a stuck pedal or cable is the most likely problem
    And then the FUN really starts! Had it happen on my first 504, a Ti. Ended up in a ditch as the throttle had jammed down at 100 km/h when the late braking for the 50 km/h Esses didn't go to plan. I was but a callow youf of 20 and had a proper Euro not the POS Holden I had worn out/broken and got thoroughly sick of fixing. "Holden's are so reliable, nothing ever goes wrong." Brendan.

  8. #8
    1000+ Posts jo proffi's Avatar
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    Quote Originally Posted by neil s View Post
    All of the above with a sticking accelerator cable [or a broken one] the prime suspect. When you find it put a second spring onto the accel. linkages on the carby to ensure that the throttle stays off unless pushed. It doesn't have to be a very strong spring to help. Neil
    Can you have too many springs pulling the throttle closed??

    My car has a clock spring on the throttle axle, a coil spring on the throttle spindle and another on the linkage between the throttle and the cable receiver cam plate.
    It makes the go pedal a little heavier ( not a bad thing on a short travel pedal) which occasionally helps economy.

    Jo

  9. #9
    1000+ Posts Peter Chisholm's Avatar
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    I'd rather fit a new accelerator cable than install extra springs.

  10. #10
    1000+ Posts Wildebeest's Avatar
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    A possibility that the cable has jumped off the carb drum and it's now pulling tighter?

    Is it an automatic ? The kick-down cable may have siezed or something.

  11. #11
    Member pugperson's Avatar
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    Unlikely in this instance, but I've had countless experiences with various cars where rubber mats or extra carpet in the driver's footwell has bunched up and either depressed the pedal or wedged in such a way to interfere with the cable or linkage. So much so that it's something I check every time I get in any of my cars, and from time to time on a long drive.
    Neil

    1977 504 GL

    (see it at http://www.grouseguitars.com.au/peugeot )

  12. #12
    Fellow Frogger! julian b's Avatar
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    Another possibility is fraying of the inner cable at the firewall where it leaves the outer cable . Mine was frayed because it was being pulled sideways because of RHD conversion when new .The solution was to drill a new hole in the right place in the firewall and fit a new cable

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