Introduction to Engines
Internal Combustion
Engine Parte - Parte
What Can Go Wrong?
Engine Subsystems
How to Help an Engine Produce More Power
Maximum Fuel Efficiency
What Can Go Wrong
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 run-down 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.
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BACK TO CONTENTS
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Introduction to Engines
Internal Combustion
Engine Parte - Parte
What Can Go Wrong?
Engine Subsystems
How to Help an Engine Produce More Power
Maximum Fuel Efficiency
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