Results 1 to 20 of 20

Thread: dieseling problem

Forum to discuss Austin Healey Sports Cars

  1. #1
    Freshman Member
    Join Date
    Jun 2015
    Location
    Savannah, Georgia
    Posts
    18
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    dieseling problem

    Dieseling on my BJ8 since we put in new electronic ignition. Same 91 octane non-ethanol gas, rebuilt tuned carbs before ignition install, supposedly properly adjusted timing.... What else could it be??

  2. #2
    Jedi Trainee
    Join Date
    Dec 2015
    Location
    Edgewood, NM
    Posts
    222
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    3
    Thanked in
    2 Posts

    Re: dieseling problem

    A few thoughts: Did the car diesel after rebuilding and tuning the carbs, but before the new ignition system was installed? Did you check the timing with a timing light? Could there be any vacuum/air leaks after rebuilding and installing the carbs? Are the float levels set correctly, and are the float valves in good condition? GL, Jim

  3. #3
    Yoda
    Join Date
    Feb 2007
    Location
    California USA
    Posts
    3,522
    Thanks Thanks Given 
    1
    Thanks Thanks Received 
    23
    Thanked in
    20 Posts

    Re: dieseling problem

    Idle speed? The most common cause of dieseling--assuming timing, etc. is correct--in my experience is idle speed set over 750RPM.

  4. #4
    Freshman Member
    Join Date
    Jun 2015
    Location
    Savannah, Georgia
    Posts
    18
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: dieseling problem

    No, did not diesel after carb rebuild. My man has supposedly checked the timing--with a light, I don't know. The rest i will run by him as I am not doing to work. Many thanks for you help.

  5. #5
    Jedi Warrior
    Join Date
    Nov 2011
    Location
    Martinsville NJ
    Posts
    467
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    1
    Thanked in
    1 Post

    Re: dieseling problem

    My idle went up after switching to Petronix without any other changes. Lower the idle, and, or, step on the clutch when you shut it off.

  6. #6
    Yoda John Turney's Avatar
    Join Date
    May 2002
    Location
    Concord, CA
    Posts
    3,080
    Thanks Thanks Given 
    19
    Thanks Thanks Received 
    9
    Thanked in
    8 Posts

    Re: dieseling problem

    I agree with Bob.
    John, BN4

  7. #7
    Yoda Michael Oritt's Avatar
    Join Date
    Jun 2001
    Location
    Lusby, MD, USA
    Posts
    3,000
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    8
    Thanked in
    8 Posts

    Re: dieseling problem

    I don't know why switching to an electronic ignition alone would cause running on but I would inspect and perhaps change the plugs to one grade colder. Also I think your car would benefit from better fuel.

    Best--Michael Oritt
    1954 Austin-Healey 100 Le Mans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

  8. #8
    Yoda HealeyRick's Avatar
    Join Date
    Apr 2004
    Location
    Massachusetts
    Posts
    5,479
    Thanks Thanks Given 
    8
    Thanks Thanks Received 
    15
    Thanked in
    13 Posts

    Re: dieseling problem

    First thing I'd do if it's not too difficult is to change the ignition back to what it was and if the dieseling stops you've isolated your problem. If it's ignition relate, I wonder if a hotter spark that's keeping the combustion chamber hotter and allowing the remaining fuel to ignite after shut off. Also possible there's some carbon buildup in the combustion chambers that stays glowing after shut down, causing the diesel. In order of what I'd do is check for raised idle speed, revert to regular ignition and try colder plugs.
    Rick

  9. #9
    Jedi Trainee
    Join Date
    Dec 2015
    Location
    Edgewood, NM
    Posts
    222
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    3
    Thanked in
    2 Posts

    Re: dieseling problem

    Michael and Rick make interesting suggestions. I now remember a problem back in the '70s. A friend had a similar issue with his Spitfire. He had changed the plugs and other ignition parts, but had not checked that the plugs were the correct heat range- or at least the same type that he had been using. The car dieseled badly, and he chased the problem for a couple of weekends, unfortunately messing up almost everything that he could adjust. An "old guy" (probably about 31) that we knew figured out the new plugs were two steps hotter. Replacing them with the original parts solved the problem.

    Were your plugs changed?

    As to the electronic ignition, I assume (and that can be bad!) that by replacing the points with the pick-up hardware for the electronic ignition, the timing could have advanced (like adjusting the points affects the timing). That could cause the car to run on. Jim
    Last edited by Jim 58 BN6; 10-08-2017 at 01:59 PM. Reason: typos

  10. #10
    Yoda Michael Oritt's Avatar
    Join Date
    Jun 2001
    Location
    Lusby, MD, USA
    Posts
    3,000
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    8
    Thanked in
    8 Posts

    Re: dieseling problem

    Any little thingie that lights up in the combustion chamber can cause running on--carbon deposits, sharp edges, crap on spark plugs from crummy gas, etc. Also improper ignition timing can be a cause, resulting in things lighting up at the wrong time in the ignition sequence, causing running on and other issues.

    I see that you are "not doing your own work" and this is a great place to begin learning. Invest in a timing light and check it out yourself--even if you don't rectify the problem you'll have acquired new knowledge and feel that much more confident about owning your Healey. Get the kind with an digital advance--it is easier to use and can also verify your tach's reading.
    Last edited by Michael Oritt; 10-09-2017 at 09:04 AM.

    Best--Michael Oritt
    1954 Austin-Healey 100 Le Mans
    1958 Elva Courier (FOR SALE)
    1959 Elva MK IV Sports Racer
    1961 Ginetta G4

  11. #11
    Jedi Knight TimK's Avatar
    Join Date
    May 2008
    Location
    Michigan
    Posts
    1,031
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: dieseling problem

    Then there is always this: let out the clutch and stall the engine after turning the ignition off.
    Tim K.
    1960 3000 BN7 (owned since 1981)
    1973 Yamaha TX500 (Owned since new -- 11,000 lifetime miles)
    Former LBCís: 1961 TR3, 1966 MGB (SCCA race car)
    First car: Volvo 122S

  12. #12
    Freshman Member
    Join Date
    Jun 2015
    Location
    Savannah, Georgia
    Posts
    18
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: dieseling problem

    The old clutch trick is what I have been doing, but knowing something is not right brothers me. Perfectionism has its costs.

  13. #13
    Jedi Warrior red57's Avatar
    Join Date
    Apr 2008
    Location
    Washington, USA
    Posts
    421
    Thanks Thanks Given 
    4
    Thanks Thanks Received 
    7
    Thanked in
    7 Posts

    Re: dieseling problem

    Then there is always this: let out the clutch and stall the engine after turning the ignition off.
    That's the way I always do it. Mine runs on some times but not always and in almost all cases I want it in gear when I park, so I roll up to a stop, put it in 1st, turn key off, lift clutch.
    It becomes habit and is no inconvenience at all (and no one knows you have a dieseling problem).
    Dave

  14. #14
    Yoda HealeyRick's Avatar
    Join Date
    Apr 2004
    Location
    Massachusetts
    Posts
    5,479
    Thanks Thanks Given 
    8
    Thanks Thanks Received 
    15
    Thanked in
    13 Posts

    Re: dieseling problem

    If you buy your own timing light, make sure it is compatible with your electronic ignition. Some lights won't work with certain ignition electronics.
    Rick

  15. #15
    Jedi Trainee
    Join Date
    Dec 2015
    Location
    Edgewood, NM
    Posts
    222
    Thanks Thanks Given 
    5
    Thanks Thanks Received 
    3
    Thanked in
    2 Posts

    Re: dieseling problem

    Quote Originally Posted by HealeyRick View Post
    If you buy your own timing light, make sure it is compatible with your electronic ignition. Some lights won't work with certain ignition electronics.
    Many newer lights seem to be poorly shielded, so the ignition noise from older cars may interfere with their measurement - in some cases a lot. The inductive pick-up can also be trouble. Personally, I would be wary of timing lights from Harbor Freight and other discount stores. You don't need to spend a fortune for a Snap On brand timing light, but a bit of research might save a lot of frustration.

  16. #16
    Jedi Hopeful 4tecdog's Avatar
    Join Date
    Oct 2015
    Location
    Wales uk
    Posts
    130
    Blog Entries
    1
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: dieseling problem

    May not be related to healeys but worth checking thermostat and general cooling & ventilation we often get run on in marine engines with the issue of poor air flow usually run engine at idle for a period before shut down cures the problem.

  17. #17
    Senior Member
    Join Date
    Feb 2014
    Location
    Freeport, Maine
    Posts
    54
    Thanks Thanks Given 
    1
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Re: dieseling problem

    It is very comforting to see how frequently so many of us need to stall the engine after shutting it off. It’s not a problem...it’s a feature.
    1955 Austin Healey 100

  18. #18
    Yoda steveg's Avatar
    Join Date
    Sep 2007
    Location
    Altadena, CA
    Posts
    3,083
    Thanks Thanks Given 
    35
    Thanks Thanks Received 
    42
    Thanked in
    40 Posts

    Re: dieseling problem

    Quote Originally Posted by 4tecdog View Post
    May not be related to healeys but worth checking thermostat and general cooling & ventilation we often get run on in marine engines with the issue of poor air flow usually run engine at idle for a period before shut down cures the problem.
    Thank you 4tecdog! Will try this out.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow

  19. #19
    Yoda steveg's Avatar
    Join Date
    Sep 2007
    Location
    Altadena, CA
    Posts
    3,083
    Thanks Thanks Given 
    35
    Thanks Thanks Received 
    42
    Thanked in
    40 Posts

    Re: dieseling problem

    Quote Originally Posted by moremonkey View Post
    It is very comforting to see how frequently so many of us need to stall the engine after shutting it off. Itís not a problem...itís a feature.
    I remember air-cooled VWs had an anti-dieseling solenoid on the carb which would shut off the flow of fuel from the float chamber when the ignition was turned off. Would that we had such a device on our HD-series carbs on the bottom between the float bowl and main jet.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow

  20. #20
    Yoda
    Join Date
    Feb 2007
    Location
    California USA
    Posts
    3,522
    Thanks Thanks Given 
    1
    Thanks Thanks Received 
    23
    Thanked in
    20 Posts

    Re: dieseling problem

    Quote Originally Posted by steveg View Post
    I remember air-cooled VWs had an anti-dieseling solenoid on the carb which would shut off the flow of fuel from the float chamber when the ignition was turned off. Would that we had such a device on our HD-series carbs on the bottom between the float bowl and main jet.
    With Lucas electrics? Remember the 'automatic' enrichment circuits?

Bookmarks

Posting Permissions

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