Carboned up Valves

I have never had this happen, but when trying to start our old Volvo, you couid hear the starter motor turn, but there the engine didn’t turn over. The AAA guy called this a carbon lock, the Daisywagon folks called it carboned up valves. Not much on the web about this.
But apparently, if you’ve run a car relatively slowly or just for a short period, then the gasoline (which is injected behind the valves and then it flows into the piston) builds up behind the valve and they stick open.
When this happen, the start motor spins, but since the valve(s) are stuck open, there is no compression. The preventive fix is:
1. Make sure to run the car regularly and get it up to high operating temperature so that the gas burns cleanly
2. If you have this condition where the starter spins and there is no turning over, then make sure your battery is good and has lots of charge and you then have to push the gas pedal down and crank for a long time, this puts lots of fuel in and hopefully, the valve will then unstick.
3. Be careful when it starts though as you will have the engine racing along, not to mention buckets of fuel in the car. When the AAA started it finally, there was lots of smoke from the unburned fuel and plenty of raw fuel coming out of the exhaust!

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