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Engine run-on after stopping.

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John_Progess

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I can't seem to get my 64 BJ8 engine to stop running after the switch is turned off. I have adjusted the timing from about 10 deg BTDC to about 18 deg BTDC in about 2 deg increments and it hasn't seemed to help much. It has been completely rebuilt. I checked the maximum advance and it was about 35 deg at about 3500 rpm. Any suggestions? Thanks and have a good day!

John
 
Hi John,

The first thing that comes to mind is ; Are you using premium
gasoline ? Regular may tend to diesel on after turning off the ignition switch.

Ed
 
Check archives. This comes up all the time. You may be off on carb setting. Pull plugs (at least one form the first three and one from the rear three)and check color of electroid. Look for a nice even tan. Black is too rich. Use good gas (high octain). Some Healeys just run on (diseling) because the engine is hot and continues to ignight the residual fuel in the chambers. You can put it in gear and lift the clutch to stop it. But my guess is that you have the carbs too rich. Ok guys, jump all over me.
TH
 
Ed,
Didn't know premium was necessary, so I guess I will go down and fill up with premium. The tank is about 1/2 empty. I will empty it somemore before I go fill it up.
TH,
The carbs were way rich when I first started the engine after restoration. I used a colortune and adjusted them about right. Now there is very little soot in the tailpipe and the plugs look about right. One thing I find is that the slow run needle is about 7 turns up and this seems way high. It seems to take along time for it to settle down to an idle and then sometimes the rpm seems to wonder a bit. The acceleration seems flat aroung 3000 rpm. The engine temp is about 195 to 200 deg F. Thanks for the help and have a good day!

John
 
John, I know this is challenging sometimes, and maybe not anyone of use has the right answer because we're not there seeing what you are seeing. 7 turns on the slow run screw does seem alot. What is your engine idling at with that adjustment. A fast idle and advanced timing will contribute to a run-on condition. The timing should not have to be more than 3/4ths inch counterclockwise from TDC. That would equate to about 15 degrees advanced. 5/8ths inch is about 12 degrees advanced. If you decrease the timing advance the engine "WILL" slow down, this would help to reduce the posibility of run-on.
About the engine feeling flat excelleration at about 3000 rpms... If you have advanced the static timing beyond what the engine/cam combination needs for its optimum performance, you tend to change at what rpm the total timing, (static + vacum + centrifical), is all in. If the total timing is all in at around that 3000 rpm mark, then excelleration could be affected beyond that point. I know if I keep my static timing at between 12 and 15 degrees, my idle is better and my acceleration is more lineal all through the RPM range.
Dave C.
 
John-

All six cylinders run high compression, they were made in the days of high test gas. Run premium, and I have had good results with Bardahls insted o lead gold, which is very effective as an octane boost.

Also, when turning off the car, do it with your foot on the clutch, and then release as you shut off the motor, it will stop the running on. Most healey owners I know do this.
 
Did you do throttle Shafts or bushings, when carbs were overhauled? If wear is present air will be drawn though shafts making mixture lean at idle& hard to adjust. Many times people compensate by enriching mixture at idle& causing rich mixture or loading up. Also causes run-on, too much fuel & throttle plate angle open to wide. Since there is no fuel shut-off provision, as long as there's vacuum engine will draw fuel& any glowing carbon in cyl. head will ignite mixture.cheersGenos2 PS: healeynut is right shut off in gear and let clutch out works-its all a matter of timing, foot&key.
 
Dave,
I am setting the idle at 600 rpm. I don't know if the tach is correct but this car will idle easily down to 300 rpm. So far I have been unable to get a steady idle. After I stop sometimes it idles fine sometimes it idles fast (1000 rpm) and sometimes it will be down around 300 rpm. The timing mark for 15 deg BTDC should be around .8 inches from the TDC mark in the clockwise direction as viewed from the front of the car. Is this correct? I just went for a ride after filling up with premium and the car did not run-on after stopping. I did install new shaft bushings during the carb overhaul. The car still seems to labor around the 3000 rpm mark. It could very well be that I am not used to the engine response yet. I will keep trying till I get it right! Thanks for the help and have a good day!

John
 
Check the vacuum advance for suction and that you have the right springs on the advance weights. You may have a vacuum leak or broken actuator (big round thing at the dizzy).
Invest in a timing light that has the advance you can set to the desired degrees. Harbor Freight has them for something in the 20 dollar range. It will make life easier. I have a good ($$$) Craftsman I got on Ebay for 20 bucks.
 
Tahoe,
I ran the rpm up to 3500 and the timing advanced to about 34 deg BTDC. Does this indicate that the advance is working? How do I identify the springs and what should I have? Thanks again and have a good day!

John
 
I think you are okay if it advances that much. I believe Dave Russell (RIP)suggested that exact amount. How are you measuring the 34 degrees?
 
re:
"I am setting the idle at 600 rpm. I don't know if the tach is correct but this car will idle easily down to 300 rpm. So far I have been unable to get a steady idle. After I stop sometimes it idles fine sometimes it idles fast (1000 rpm) and sometimes it will be down around 300 rpm."


Your choke/fast idle circuit(s) might be hanging up. This is a common problem on HD carburetors. Make sure the choke levers are all the way down before checking idle, etc. Sounds like you may have the idle set low--i.e. 300rpm--and the choke levers may be sticking, causing the fast idle circuit to, well, make the engine idle fast.

As someone else suggested, this could be an intake leak. A vacuum gauge plumbed into the plugged hole on the intake manifold might provide some insight.
 
Tahoe,
The length along the circumference of the pulley. The pulley is 6.25 " diameter so 34 deg is 1.854" from the TDC mark on the pulley.
Bob,
I will check that out today. I have been able to solve all the problems so far except the random idle. Thanks for the help and have a good day!

John
 
That seems like such a waste of time when you use the timing light for many different desired RPMs. You really ought to check it out. I carry mine in the boot cause it is so useful.
 
Engine run on! My 100 bn-1 did the same. It has a 10.35:1 compression ratio, M spec cam and 1.75" carbs. I adjusted the timing, changed the distributor, fixed the vacuum advanced unit, changed to plugs for Autolite "very cold" ones, got rid of the points, adjusted the carbs, heck I did every thing and finally decided it was going to run that way regardless of what I did.

Well I recently changed my engine mount rubber blocks cos the engine rocked a little too much! To do this I had to remove the carbs "I also had an oil leak from the tappet cover on the side of the engine."

I put everything back, using new gaskets and this time, plenty of gasket sealer and I no longer have a run on problem.

I adjusted no timing, carb or other setting other than the carb balance.

I must have had a vacuum leak on one of the carb flanges that only showed up once the engine was hot.

You might want to check to see if you also have an air leak as your erratic idle suggests that you might.
 
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