Results 1 to 8 of 8

Thread: Engine dieseling??

  1. #1
    Senior Member
    Join Date
    Jun 2013
    Location
    lynchburg, Va
    Posts
    543

    Engine dieseling??

    The last two times I drove my car the engine dieseled for several seconds when I turned off the key. What is the likely cause?? Nothing has been changed otherwise. Always ran very well without issues.
    1969 911S Targa
    1970 911S Coupe
    1973 911T w 3.2
    1972 Alfa GTV 2000

  2. #2
    Member
    Join Date
    May 2013
    Location
    Victoria BC Canada
    Posts
    58
    You didn't say what car you have the trouble with, but typically dieseling, or run-on can be caused by an idle speed that is set too high on a carbureted engine or by low octane fuel, (fuel vapours continue to burn from heat in the cylinders). Higher octane is less volatile.
    Cheers,

    Jones...
    early S # 2626
    '71 911T
    '68 Peugeot 204
    '65 Mustang (sold after 32 years)
    1922 Wills Sainte Claire

  3. #3
    Senior Member
    Join Date
    Jun 2013
    Location
    lynchburg, Va
    Posts
    543
    Quote Originally Posted by Jones View Post
    You didn't say what car you have the trouble with, but typically dieseling, or run-on can be caused by an idle speed that is set too high on a carbureted engine or by low octane fuel, (fuel vapours continue to burn from heat in the cylinders). Higher octane is less volatile.
    Sorry--1970 911S Coupe
    1969 911S Targa
    1970 911S Coupe
    1973 911T w 3.2
    1972 Alfa GTV 2000

  4. #4
    Serial old car rescuer Arne's Avatar
    Join Date
    Aug 2011
    Location
    Eugene, OR
    Posts
    1,565
    I'm betting on a bad tank of gas. Too much ethanol, or lower than advertised octane.
    - Arne

    Mostly done
    - 1972 911T coupe, Silver Metallic, Fuchs, Appearance Group, F&R sway bars, factory installed Frankfurt. Soon to regain factory A/C.
    Sold - 1984 911 Carrera coupe, Chiffon white; 1973 914 2.0, Saturn Yellow; 1984 944, Silver Metallic

  5. #5
    Senior Member majordad's Avatar
    Join Date
    Dec 2012
    Location
    Cork , Ireland
    Posts
    418
    Same often happens to my 1972 S, and I’ve been told it’s due to the engine running rich.

  6. #6
    Senior Member 72targa's Avatar
    Join Date
    Feb 2004
    Location
    SF/Bay Area, CA
    Posts
    11,316
    Would love to hear from Ed on this interesting topic...

    Here’s a generic article...

    https://axleaddict.com/auto-repair/W...-Keeps-Running
    Peter Kane

    '72 911S Targa
    Message Board Co-Moderator - Early 911S Registry #100

  7. #7
    Senior Member
    Join Date
    Jun 2013
    Location
    lynchburg, Va
    Posts
    543
    Quote Originally Posted by Arne View Post
    I'm betting on a bad tank of gas. Too much ethanol, or lower than advertised octane.
    I think we have a winner. Filled up with fresh tank of Shell premium and no more issues--not even a hint of run-on. Added a can of Seafoam to remove any excess carbon from cold weather driving, etc. Took a long drive. Runs great again.
    1969 911S Targa
    1970 911S Coupe
    1973 911T w 3.2
    1972 Alfa GTV 2000

  8. #8
    Moderator Chuck Miller's Avatar
    Join Date
    Oct 2002
    Location
    Reseda, CA.
    Posts
    11,445
    Great advice, great outcome.... congrats Frank !!!
    Chuck Miller
    Creative Advisor/Message Board Moderator - Early 911S Registry #109
    R Gruppe #88

    TYP901 #62
    '73S cpe #1099 - Matched # 2.7/9.5 RS spec rebuild
    '67 Malibu 327 spt cpe - Period 350 Rebuild

    98 Chevy S-10 Utility
    15 GTI Commuter

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Message Board Disclaimer and Terms of Use
This is a public forum. Messages posted here can be viewed by the public. The Early 911S Registry is not responsible for messages posted in its online forums, and any message will express the views of the author and not the Early 911S Registry. Use of online forums shall constitute the agreement of the user not to post anything of religious or political content, false and defamatory, inaccurate, abusive, vulgar, hateful, harassing, obscene, profane, sexually oriented, threatening, invasive of a person's privacy, or otherwise to violate the law and the further agreement of the user to be solely responsible for and hold the Early 911S Registry harmless in the event of any claim based on their message. Any viewer who finds a message objectionable should contact us immediately by email. The Early 911S Registry has the ability to remove objectionable messages and we will make every effort to do so, within a reasonable time frame, if we determine that removal is necessary.