View Full Version : Engine will not stop

Jim R. Walker
07-13-2002, 06:55 PM
Ok - could someone help me? I have a 67 BJ8 that runs great except when I turn off the ignition the engine runs a few more moments and coughs, shakes before finally turning itself off.

I tried looking at the various manuals, Haynes etc but can not locate this problem or solution.

Thank you.

07-13-2002, 07:22 PM
Called "running on", I believe that this is an indication of the mixture being too rich. It could also be an indication of a buildup of carbon on the cylinder head, although I think the rich mixture theory is more likely. Adjusting the carbs may help, but always do the easy checks first. Is the air filter clogged up? If the engine isn't breathing right, that might contribute to the problem. If the choke is sticking on that might also cause problems.

P.S. Welcome to the forum! images/icons/grin.gif

[ 07-13-2002: Message edited by: Steve ]</p>

07-14-2002, 02:16 PM
Welcome to the forum.
I believe the problem is a combination of carbon buildup and timing that is a bit off.

07-14-2002, 02:48 PM
As stated in earlier posts, this is usually due to carbon buildup that stays hot enough to ignite the fuel without assistance from the plugs. If it's a mild case, a higher octane fuel often eliminates it (it has a higher flash point). Of course, this isn't an option if you already use premium gas. Opening the throttle fully sometimes helps (after you switch off) by reducing temps but this may not work with SU's (pistons will block most of the bore).

"Running-on" like this sounds awful but doesn't hurt anything. However, cars that do this often are pre-igniting ("pinging") while driving which can burn valves. Retarding the timing a little and higher octane can help. A slightly richer mixture can sometimes work.

Eventually, the carbon should be removed. Older engines needed this done frequently (it was usually called "De-coking", one of my favorite maintenance expressions) probably due to the nasty fuels used back then.

John C

Jim R. Walker
07-14-2002, 11:38 PM
Wow... thanks for all the help. Gee.... I just got involved with this forum. I appreciate the help, suggestions and acceptance from you experienced owners. I hope someday I can return the help.

images/icons/smile.gif Jim

07-15-2002, 09:04 AM
I agree with all other comments listed, but would also like to add: check idle speed. If it's too high, car will "run-on". Also, be sure it's not running hot (themostat, etc.)

For a varity of reasons, my car does this on occasion (carb/cam combo won't allow real low idle).....I "stall" the engine by letting the clutch out in 3rd gear immediately after switching off the ignition. Not exactly elegant, but it works (be sure you have right foot on the brake if you do this).

Re "de-coking"...there's a great section about this in the TR-3 owners manual (advised every 10,000 miles!). Fortunately, unleaded fuel mostly eliminates this problem.

[ 07-15-2002: Message edited by: aeronca65t ]</p>

John Turney
07-15-2002, 12:53 PM
I've had this problem appear occasionally over the years. The last time it was a sharp corner on a spark plug electrode. It would get/stay hot enough to ignite the mixture. I've also found that running lean can increase the combustion chamber temperature and cause deposits to glow. It sometimes helps to give it a good run at speed graemlins/devilgrin.gif .


Ken G
07-15-2002, 01:58 PM
On the subject of decarbonizing engines, some of you might be amused at the instructions for my 1925 Rover, to be found on pages 34-35 of the service manual. See https://mywebpage.netscape.com/rover1927/index.htm

(For the sharp-eyed, the car was built in 1925 as a 14/45 and upgraded in 1927 to a 16/50; the manuals are substantially identical).

Ken G, 1925 Rover 16/50

07-16-2002, 11:20 AM
Jim R.,
I have had the same problem with my healey. You can try to adjust your carbs or your timing, that is if you know how or trust yourself to do it. I do not trust myself? I researched this problem " running on" and it is not uncommon. I also concluded that a higher octane fuel may help to clean out the cylinders. I have used a product called Bardahl's octane boost. I use it about every third or fourth fillup and then only 1/3 the amount specified. I have been doing this for approximately 2 1/2 years and I have not had a problem with "diesling" or " running on" since. Could some of the more experienced healeyists please comment on my solution?

07-17-2002, 12:24 PM
I've been through this recently. So, here goes:
Use high octane gas. AH have hi compression pistons.
Use the proper spark plugs.
Check timing and adjust carbs.
Failing all the above, pull the head decoke and take the sharp edges off the head with a dremel. The sharp edges are hot spots and will ignite the remainging gas- run on.

Good luck