Diagnosis And Testing - Cylinder Compression Pressure Test - Chrysler PT Cruiser Service & Repair Manual

9 - 8 ENGINE 1.6L SOHC
ENGINE 1.6L SOHC (Continued)
CONDITION
OIL CONSUMPTION OR SPARK
PLUGS FOULED
DIAGNOSIS AND TESTING - CYLINDER
COMPRESSION PRESSURE TEST
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Check engine oil level and add oil if necessary.
(2) Drive the vehicle until engine reaches normal
operating temperature. Select a route free from traf-
fic and other forms of congestion, observe all traffic
laws, and accelerate through the gears several times
briskly.
CAUTION: When removing spark plugs, use Special
Tool 8448 Protective Sleeve on extension (Fig. 2) or
damage to spark plug tubes may result.
(3) Remove all spark plugs from engine. As spark
plugs are being removed, check electrodes for abnor-
mal firing indicators fouled, hot, oily, etc. Record cyl-
inder number of spark plug for future reference.
(4) Remove the Auto Shutdown (ASD) relay from
the PDC.
(5) Insert compression gauge adaptor Special Tool
8116 or the equivalent, into the #1 spark plug hole in
cylinder head. Connect the 0–500 psi (Blue) pressure
transducer (Special Tool CH7059) with cable adap-
tors to the DRBIII . For Special Tool identification,
(Refer to 9 - ENGINE - SPECIAL TOOLS).
(6) Crank engine until maximum pressure is
reached on gauge. Record this pressure as #1 cylin-
der pressure.
POSSIBLE CAUSES
1. PCV system malfunction.
2. Worn, scuffed or broken rings.
3. Carbon in oil ring slots.
4. Rings fitted too tightly in grooves.
5. Worn valve guide(s).
6. Valve stem seal(s) worn or
damaged.
(7) Repeat the previous step for all remaining cyl-
inders.
(8) Compression should not be less than 689 kPa
(100 psi) and not vary more than 25 percent from cyl-
inder to cylinder.
(9) If one or more cylinders have abnormally low
compression pressures, repeat the compression test.
(10) If the same cylinder or cylinders repeat an
abnormally low reading on the second compression
test, it could indicate the existence of a problem in
the cylinder in question. The recommended com-
pression pressures are to be used only as a
guide to diagnosing engine problems. An engine
should not be disassembled to determine the
cause of low compression unless some malfunc-
tion is present.
1. Check system and repair as
necessary. (Refer to 25 -
EMISSIONS CONTROL/
EVAPORATIVE EMISSIONS/PCV
VALVE - DIAGNOSIS AND
TESTING)
2. Hone cylinder bores. Install new
rings.
3. Install new rings.
4. Remove rings and check
grooves. If groove is not proper
width, replace piston.
5. Replace cylinder head.
6. Replace seal(s).
Fig. 2 Special Tool 8448 Protective Sleeve
PT
CORRECTION