Engine Problems
So you go out one morning and your engine will
turn over but it won't start... What could be wrong? Now that you know how an
engine works, you can understand the basic things that can keep an engine from
running. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark Beyond that,
thousands of minor things can create problems, but these are the "big
three." Based on the simple engine we have been discussing, here is a
quick rundown on how these problems affect your engine:
Bad fuel mix - A bad fuel mix can occur in several ways:
·
You are out of gas, so the engine
is getting air but no fuel.
·
The air intake might
be clogged, so there is fuel but not enough air.
·
The fuel system might
be supplying too much or too little fuel to the mix, meaning that combustion
does not occur properly.
·
There might be an
impurity in the fuel (like water in your gas tank) that makes the fuel not
burn.
Lack of compression - If the charge of air and fuel cannot be
compressed properly, the combustion process will not work like it should. Lack
of compression might occur for these reasons:
·
Your piston rings are
worn (allowing air/fuel to leak past the piston during compression).
·
The intake or exhaust
valves are not sealing properly, again allowing a leak during compression.
·
There is a hole in the
cylinder.
The most common "hole" in a cylinder
occurs where the top of the cylinder (holding the valves and spark plug and
also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and
the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If
the gasket breaks down, small holes develop between the cylinder and the
cylinder head, and these holes cause leaks.
Lack of spark - The spark might be nonexistent or weak for a
number of reasons:
·
If your spark plug or
the wire leading to it is worn out, the spark will be weak.
·
If the wire is cut or
missing, or if the system that sends a spark down the wire is not working
properly, there will be no spark.
·
If the spark occurs
either too early or too late in the cycle (i.e. if the ignition timing is off), the fuel will
not ignite at the right time, and this can cause all sorts of problems.
Many other things can go wrong. For example:
·
If the battery is dead, you cannot turn over the engine to start it.
·
If the bearings that allow the crankshaft to turn freely are worn out, the
crankshaft cannot turn so the engine cannot run.
·
If the valves do not
open and close at the right time or at all, air cannot get in and exhaust
cannot get out, so the engine cannot run.
·
If someone sticks a
potato up your tailpipe, exhaust cannot exit the cylinder so the engine will
not run.
·
If you run out of oil,
the piston cannot move up and down freely in the cylinder, and the engine will
seize.
In a properly running engine, all of these
factors are within tolerance.
As you can see, an engine has a number of
systems that help it do its job of converting fuel into motion. We'll look at
the different subsystems used in engines in the next few sections.
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