Mechanics

WARM WEATHER START/RUN

1995 Mercedes Benz SL500

Engine Performance problem
1995 Mercedes Benz SL500 V8 Two Wheel Drive Automatic 60000 miles

Engine starts and runs well except after shut off on short trips during warm weather. It does not want to start. Trys to fire, backfires, misses. I have always been able to coax it to run but very rough even when I get it to city speeds.
I had received an email from Ken Lavacot acknowleging my donation of $20 but apparently was not successful in sending message. Can you help and will my payment get to proper person?
Thank you. GLG
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Georgegreen
June 10, 2010.




Hello and thanks for donating

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.

Bluelightnin6
Jun 26, 2010.


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