Engine Compression Test; Cylinder Leakage Test - Suzuki XL7 2007 Service Manual

1D-34 Engine Mechanical:

Engine Compression Test

Special tool
J 39313 Spark Plug Port Adapter
A compression pressure test of the engine cylinders
determines the condition of the rings, the valves and the
head gasket.
1. Run the engine until it reaches normal operating
temperature. The battery must be at or near full
charge.
2. Turn the engine OFF.
NOTE
Remove the powertrain control module
(PCM) and the ignition fuse from the
instrument panel (I/P) fuse block.
3. Disable the ignition.
4. Disable the fuel systems.
5. Remove the spark plugs from all cylinders.
6. Remove the air duct from the throttle body.
7. Block the throttle plate in open position.
8. Measure the engine compression, using the
following procedure:
a. Thread the J 39313 into the spark plug hole.
b. Thread the compression gage into the J 39313.
c. Have an assistant crank the engine through, at
least 4 compression strokes, in the testing
cylinder.
d. Check and record the readings on the gage at
each stroke.
e. Remove the compression gage from the J
39313.
f. Remove the J 39313 from the spark plug hole.
g. Repeat the compression test for each cylinder.
9. Record the compression readings from all of the
cylinders.
– The lowest reading should not be less than 70
percent of the highest reading.
– No cylinder reading should be less than 965 kPa
(140 psi).
10. The following are examples of measurement
problems:
– When the compression measurement is normal,
the compression builds up quickly and evenly to
specified compression on each cylinder.
– When low compression is caused by the piston
rings, compression is low on the first stroke and
tends to build up on the following strokes, but
does not reach normal. Compression improves
considerably with the addition of oil. Use
approximately 3 squirts of oil from a plunger-type
oiler.
– When low compression is caused by the valves,
the measurement is low on the first stroke and
does not build up even with the addition of oil.
– Leaking head gaskets will provide the same
results as worn valves but engine coolant may be
identified in the crankcase. In addition, a leaking
head gasket will give low readings on paired
cylinders.
11. Remove the block from the throttle plate.
12. Install the air duct to the throttle body.
13. Install the spark plugs.
14. Install the powertrain control module (PCM).
15. Install the ignition fuses to the I/P fuse block.

Cylinder Leakage Test

Special tool
J 35667-A Cylinder Head Leakdown Tester
J 39313 Spark Plug Port Adapter
NOTE
A leakage test may be performed in order to
measure cylinder/combustion chamber
leakage. High cylinder leakage may indicate
one or more of the following:
• Worn or burnt valves
• Broken valve springs
• Stuck valve lifters
• Incorrect valve lash/adjustment
• Damaged piston
• Worn piston rings
• Worn or scored cylinder bore
• Damaged cylinder head gasket
• Cracked or damaged cylinder head
• Cracked or damaged engine block
WARNING
!
Refer to "Battery Disconnect Caution: ".
1. Disconnect the battery ground negative cable.
2. Remove the spark plugs. Refer to "Spark Plug
Replacement: ".
3. Rotate the crankshaft to place the piston in the
cylinder being tested at top dead center (TDC) of the
compression stroke.
4. Thread the J 39313 into the spark plug hole.
5. Install the J 35667-A or equivalent.
NOTE
It may be necessary to hold the crankshaft
balancer bolt to prevent the engine from
rotating.