Engine won't shut off

Thank you for your input, much appreciated

 

Bill
On UK cars and I'm sure US cars, when the throttle is closed, the second set of points kicks in retarding the ignition. This sometimes causes popping on deceleration and at idle. Just a thought. It sound like both banks are within an acceptable range, so perhaps it would be an idea to wait untill you have settled on all of the ignition factors and test again. Try top remember what you tweaked in case you have to untweak it

 

The popping on trailing throttle likely represents a lean idle mixture. It can be resolved by attending to the mixture screws on each carb, and screwing each out 1/4 turn (assuming they are correctly set at this time - see previous post concerning lean front bank).

Jim S.

 

If it is trailing throttle yes, but if, as most people do, it means taking one's foot off the throttle completely when decelerating or braking, then the retarded ignition plays a part. Doncha think?

Having said that, erring on the rich side is probably not a bad idea.

 

Dignini - by trailing throttle I refer to taking one's foot off of the accelerator and placing it on the brake, or in your lap, or in one's mouth, or where ever.

I have always thought of trailing throttle burbling or popping as a mixture issue, not as a timing issue. That is, I can ALWAYS correct it by slightly enriching the mixture.

Timing has, in my experience, led to different symptoms. When advanced, I get pre-ignition (pinging) and warmer operating temperatures. When retarded, lack of power. It has to be WAY out of specfication to cause erratic ignition, which is what the burbling or popping suggests. A lean mixture leads to incomplete combustion and accumulation of petrol in the exhaust or muffler. In addition, it causes the combustion to be hotter, which provides the catalyst for ignition of these uncombusted petrol molecules in the exhaust manifold or muffler, which we hear as burbling or popping.

Jim S.

 

Oh, by the way, in a previous post in this thread I discussed some esoteric justification for the ballast resistor. After further discussion with Jagman, I enjoyed an epiphany... well an epiphany to me and likely mundane to you guys.

The ballast resistor most likely is in place to limit current to the coil when the points are closed and the ignition is turned on, as when you brush your hair, or telephone your significant other, or apply your eye shadow or lipstick, and don't yet start the car. In this case, the 12-volt supply passes through the coil and points directly to ground. The primary resistance is approximatey 1-Ohm, which would lead to 12-amperes of current. Hence, by inserting a 1-Ohm resistor in series you limit the current to 6-amperes.

Jim S.

 

I only enjoy epiphany once a year, but what you guys do in private is definetly off topic

 

"I only enjoy epiphany once a year, but what you guys do in private is definetly off topic"

LOL

Jim S.

 

Jim, I'm glad to hear you brush your hair, telephone your significant other, and apply your eye shadow and lipstick before you start your Dino. It would be too dangerous for you to do that while driving. LOL.

 

I kinda like a popping exhaust. My XK120 does it. It's caused by a lean mixture when the carbs are in the idle position and the engine is at an above idle rpm. It's normal. It just means that the fuel is not burning in the cylinders but builds up in the exhaust. When enough fuel accumilates, exhaust gases ignite it in the muffler and a pop results. When the rpm drops to idle, the mixture in the cylinders is correct for closed carbs. The popping goes away and the car idles properly.