1995 Mercedes Benz SL500 warm weather start/run

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Just to clarify, your having hard starts while the engine is already warm, correct? Hot engine hard starting tends to be a seasonal problem, but may be worse in the early months of spring when refiners are switching fuel blends. Gasoline refiners produce fuel with a slightly lower volatility rating (called "Reed vapor pressure") during hot summer months because lower volatility fuel is less likely to boil and cause hot starting problems. During the winter, they switch to a higher volatility fuel because it makes cold starting easier. But if you still have "winter" grade fuel in your tank when warm spring weather arrives, you may experience some hot starting problems. The problem will go away, however, as soon as the refiners in your area switch to their summer grade fuel.

Hot starting problems can also be caused by cooling problems that allow your engine to run too hot (the pistons swell up and may scuff the cylinder walls), or excessive resistance in the starter motor that causes the engine to crank slowly. A starter "amp draw" test can be used to check the condition of your starter. Also, many starters have small "heat shields" to protect them from heat radiating from nearby exhaust pipes or manifolds. If the shield is missing, the starter may get too hot and bind up.