|The MGA With An Attitude
STARTER DUTY CYCLE - SS-100
Someone thought that 10 seconds might be a long time for cranking on a starter motor. 10 seconds is not a long time. It takes longer that that to get some cars started, especially in cold weather. Starter motors have about 10% duty cycle when operating under full load, meaning you can crank on it for 1 minute out of any 10 minute period. After 1 minute of cranking, if the engine isn't running you need enough patience to walk away from it for 9 minutes to allow it to cool down. Then you can crank on it again. Respect this cardinal rule, and you should never burn out a starter motor. I have never fried a starter motor in my life, but I have known too many people who did.
If you have the spark plugs removed for no compression, and you begin with a cold starter motor, you might crank on it for up to 2 minutes (the first time only) before it gets hot enough to give it a break. You might do this to bring up oil pressure on a freshly rebuilt engine (which takes about 45 seconds) before trying to start it.