3. Perform "Fuel Line Safety Procedure". Leave the fuel pump relay removed. (see
BEFORE REPAIR
PROCEDURE [MZI-3.5]
.)
4. Remove the engine cover. (See
ENGINE COVER REMOVAL/INSTALLATION [MZI-3.5]
.)
5. Remove the dynamic chamber and throttle body as a single unit. (see
INTAKE-AIR SYSTEM
REMOVAL/INSTALLATION [MZI-3.5]
.)
6. Remove the ignition coils. (see
IGNITION COIL REMOVAL/INSTALLATION [MZI-3.5]
.)
7. Remove the spark plugs.
8. Measure the compression pressure using the following procedure.
1. Connect the compression gauge into the spark plug hole.
2. Crank the engine
a minimum of five
compression strokes and record the highest reading.
3. Repeat the test on each cylinder, cranking the engine approximately the same number of
compression strokes.
4. The indicated compression pressures are considered within specification if the lowest reading
cylinder is within
75%
of the highest reading. Refer to
COMPRESSION PRESSURE LIMIT
CHART
.
z
If the compression in one or more cylinders is low or the compression difference between
cylinders exceeds the maximum, pour a small amount of clean engine oil into the cylinder
and recheck the compression.
If the compression increases, the piston, the piston rings, or cylinder wall may be worn
and overhaul is required.
If the compression stays low, a valve may be stuck or improperly seated and overhaul
is required.
If two adjacent cylinders indicate low compression pressures, and squirting oil on the
piston does not increase compression, the head gasket may be leaking between
cylinders. Engine oil and/or coolant in the cylinders could result from this condition.
Fig. 15: Measuring Compression Pressure
Courtesy of MAZDA MOTORS CORP.
NOTE:
z
Note the approximate number of compression strokes required
to obtain the highest reading.
2007 Mazda CX-9 Grand Touring
2007 ENGINE Mechanical (MZI-3.5) - CX-9
Microsoft
Sunday, November 15, 2009 9:19:27 AM
Page 14
© 2005 Mitchell Repair Information Company, LLC.