Compression Test (Engine) – Honda Certified Used Vehicles Program

Compression Test (Engine) – Honda Certified Used Vehicles Program


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Commentator: “A compression test is a way of testing an engine’s condition without
tearing the engine apart. Engine compression is the
amount of fuel/air mixture and engines pistons pressurizes during the engines compression
stroke. Compressions that matched the manufacturers specification is essential for an engine to
run properly and efficiently. While the lack of compression is most common, it is also
possible for compression to be too strong. Over compression
can result in a problem known as ‘Detonation’, which can be very damaging to an engine’s
internal parts. The first thing a technician does when performing
an compression test is to make sure the engine is warmed up, and has reached optimum running
temperatures. Since the compression test requires engine
cranking, the battery should be at full charge. Next, the mechanic removes the EFI fuse so
that raw fuel will not be pumped into the cylinders. Remove all spark
plugs leads and then remove all spark plugs from the engine. Next, the air cleaner should
be removed. The technician uses the compression gauge to perform
the test. At one end of the tool is the actual compression gauge, and the other end is threaded
so that it can be installed into the spark plug hole.
The technician screws in the gauge with the proper hose attachment into the number 1 spark
plug hole. The technicians assistant will now crank the engine
over with the accelerator pedal fully depressed. It should crank a minimum of 3 cycles to obtain
an accurate test. The technician will note the reading and document
it on the mechanical inspection checklist. Once the mechanic has a reading from all the
engine cylinders, the mechanic can compare the readings to what
is printed in the vehicles service manual. The compression the Honda certified used vehicle
must meet the specifications printed in the manual.”
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