Crank sensor
Hot starting problems are usually fuel related.
When a hot engine is shut off, the temperature of the engine
and everything on it continues to rise for awhile as the engine
undergoes a period of "heat soak." This can cause fuel
to boil inside the carburetor bowl, fuel lines and fuel filter.
When you attempt to restart the engine, "vapor lock"
obstructs the flow of fuel and the engine doesn't want to start.
This is much less of a problem on fuel injected engines because
the fuel is usually under much higher pressure inside the injectors
and fuel line. Even so, a fuel line routed near an exhaust manifold
or a fuel rail that's exposed to a lot of heat may still suffer
the same kind of problems.
Heat soak problems such as these can sometimes be cured by
wrapping insulation around affected fuel lines, and/or installing
an insulating spacer or heat shield under the carburetor.
A Seasonal Problem
Hard 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.
Other Causes
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.
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