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Thread: 69S won’t idle

  1. #1

    69S won’t idle

    Help! For the life of me I can’t get my 69S to idle. If I close the throttle it just dies cold or warm. If I shorten the linkage to where it will idle it won’t drop the RPM’s When you shift. It will hang up for a couple of seconds at whatever RPM you were at when you let off the throttle and push the clutch in. Not good!
    I have messed with all the air screws to no avail and now have them all set at 2&1/2 out. All six stacks are drawing the same 10 KG/h on my air flow meter. Primary linkage rod off of pump is set to 114mm and the accelerator rod is adjusted to coincide with the pump linkage. Nothing is physically hanging up. The throttle bodies were rebuilt about 20 or 30 thousand miles ago, the fuel injection pump and electric fuel Pump were just rebuilt. New gas tank and lines etc. engine just received new rings and valve job. Timing is set between 30-35* at 6,000 rpm’s, new plugs and dwell on points just set.
    Other than that the car runs like a scalded cat and has excellent throttle response. sure wish it didn’t try to die at every stop. Well at least I’m getting better at my heal and toeing!
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  2. #2
    Senior Member frederik's Avatar
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    Maybe it needs a richer idle mixture via the idle mixture screw?
    1970 2.2S Elfenbeinweiss
    1972 2.4T Targa Aubergine (MFI) [For sale]
    2002 996 TT Midnight Blue
    Member #3833

  3. #3
    There is a Small spring loaded bolt on the bottom front of the injection pump. There is a corresponding hole in the shroud that looks like you could get to it from the front of the engine With a long extension. Does this adjustment change the idle? I don’t want to be adjusting things until I know what I am doing.
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  4. #4
    Moderator Chuck Miller's Avatar
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    Chuck Miller
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  5. #5
    Senior Member frederik's Avatar
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    ^^^ This also has a link to the Check Measure Adjust manual which is the MFI "bible".
    1970 2.2S Elfenbeinweiss
    1972 2.4T Targa Aubergine (MFI) [For sale]
    2002 996 TT Midnight Blue
    Member #3833

  6. #6
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    You are right to be cautious about adjusting the pump. Especially if it was only just rebuilt by a reputable rebuilder. Make sure to check all of the basic stuff like loose screws and ignition as per the CMA. Is your govenor control lever being pushed off the stop too far by your "primary linkage rod"? This will cause it too run too rich and slow. Try running it disconnected and moving it forward slightly by hand. This should tell you if its a mixture problem without having to adjust the govenor spring tension.

  7. #7
    Thanks for all the advice. I had already read all CMA info, but felt like my problem was in the linkage adjustment. Tonight I played with the main throttle linkage and the throttle body stops and found a workable compromise. Still idles a little low but doesn’t die at stop signs now and doesn’t hang up when I shift. Maybe a little more adjustment on the air mixture screws will improve it, but for now I think I’ll just enjoy driving it for awhile
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  8. #8
    Quote Originally Posted by Theunz View Post
    Thanks for all the advice. I had already read all CMA info, but felt like my problem was in the linkage adjustment. Tonight I played with the main throttle linkage and the throttle body stops and found a workable compromise. Still idles a little low but doesn’t die at stop signs now and doesn’t hang up when I shift. Maybe a little more adjustment on the air mixture screws will improve it, but for now I think I’ll just enjoy driving it for awhile
    Yes that spring loaded screw is the idle adjustment, turning it clockwise richens the mixture (WITH ENGINE OFF) A rebuilt pump comes to you with basic adjustments to start the engine, they always require final tuning by the installer. Yes, I can get pretty close seat of the pants, it would best if you used a air/fuel ratio meter.
    Early S Registry member #90
    R Gruppe member #138
    Fort Worth Tx.

  9. #9
    Thank you Ed. As usual helpful information. Looks like a good excuse to buy a new tool!
    1969 911S
    1969 Datsun 2000...worth less, but more valuable

  10. #10
    Senior Member frederik's Avatar
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    You did disconnect the microswitch to check that the RPM transducer isn’t failing and causing this problem? It is possible that it cuts fuel to the engine when you release the throttle.
    1970 2.2S Elfenbeinweiss
    1972 2.4T Targa Aubergine (MFI) [For sale]
    2002 996 TT Midnight Blue
    Member #3833

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