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COMPRESSION INSPECTION [AJ]

BME011002000212

  Warning

  • When the engine and the oil are hot, they can badly burn. Turn off the engine and wait until they are cool.

1. Verify that the battery is fully charged.

  • Recharge it if necessary. (See BATTERY INSPECTION.)

2. Warm up the engine to the normal operating temperature.

3. Perform "Fuel Line Safety Procedure." Leave the fuel pump relay removed. (See BEFORE SERVICE PRECAUTION [AJ].)

4. Remove the ignition coils. (See IGNITION COIL REMOVAL/INSTALLATION [AJ].)

5. Remove the spark plugs.

6. Install the compression gauge into the No.1 spark plug hole.

7. Crank the engine a minimum of five compression strokes and record the highest reading. Note the approximate number of compression strokes required to obtain the highest reading.

8. Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.

9. The indicated compression pressures are considered within specification if the lowest reading cylinder is within 75 percent of the highest reading. Refer to the compression pressure limit chart.

  • 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 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.

Compression pressure limit chart

kPa {kgf/cm2, psi}

Maximum pressure | Minimum pressure | Maximum pressure | Minimum pressure | Maximum pressure | Minimum pressure | Maximum pressure | Minimum pressure
--- | --- | --- | --- | --- | --- | --- | ---
924 {9.41, 134} | 696 {7.10, 101} | 1131 {11.52, 164} | 848 {8.65, 123} | 1338 {13.63, 194} | 1000 {10.20, 146} | 1544 {15.73, 224} | 1158 {11.81, 168}
938 {9.56, 136} | 703 {7.17, 102} | 1145 {11.67, 166} | 855 {8.72, 124} | 1351 {13.77, 196} | 1014 {10.34, 147} | 1558 {15.88, 226} | 1165 {11.88, 169}
952 {9.70, 138} | 717 {7.31, 104} | 1158 {11.80, 168} | 869 {8.86, 126} | 1365 {13.91, 198} | 1020 {10.40, 148} | 1572 {16.02, 228} | 1179 {12.02, 171}
965 {9.83, 140} | 724 {7.38, 106} | 1172 {11.94, 170} | 876 {8.93, 127} | 1379 {14.05, 200} | 1034 {10.54, 150} | 1586 {16.16, 230} | 1186 {12.09, 172}
979 {9.97, 142} | 738 {7.53, 107} | 1186 {12.08, 172} | 889 {9.07, 129} | 1303 {13.28, 202} | 1041 {10.62, 151} | 1600 {16.30, 232} | 1200 {12.24, 174}
933 {9.51, 144} | 745 {7.60, 109} | 1200 {12.23, 174} | 903 {9.21, 131} | 1407 {14.34, 204} | 1055 {10.76, 153} | 1055 {10.75, 153} | 1207 {12.31, 175}
1007 {10.26, 146} | 758 {7.73, 110} | 1214 {12.37, 176} | 910 {9.28, 132} | 1420 {14.47, 206} | 1062 {10.83, 154} | 1627 {16.58, 154} | 1220 {12.44, 177}
1020 {10.39, 148} | 765 {7.80, 111} | 1227 {12.50, 178} | 917 {9.35, 133} | 1434 {14.61, 208} | 1075 {10.96, 156} | 1641 {16.72, 238} | 1227 {12.51, 178}
1034 {10.54, 150} | 779 {7.94, 113} | 1241 {12.65, 180} | 931 {9.49, 135} | 1448 {14.76, 210} | 1083 {10.04, 157} | 1655 {16.87, 240} | 1241 {12.65, 180}
1048 {10.68, 152} | 786 {8.02, 114} | 1255 {12.79, 182} | 936 {9.54, 136} | 1462 {14.90, 212} | 1089 {11.10, 158} | 1669 {17.01, 242} | 1248 {12.73, 181}
1062 {10.82, 154} | 793 {8.09, 115} | 1269 {12.93, 184} | 952 {9.70, 138} | 1476 {15.04, 214} | 1103 {11.25, 160} | 1682 {17.14, 244} | 1262 {12.87, 183}
1076 {10.96, 156} | 807 {8.23, 117,} | 1282 {13.06, 186} | 965 {9.84, 140} | 1489 {15.17, 216} | 1117 {11.39, 162} | 1696 {17.28, 246} | 1269 {12.94, 184}
1089 {11.10, 158} | 814 {8.30, 118} | 1296 {13.21, 188} | 972 {9.91, 141} | 1503 {15.32, 218} | 1124 {11.46, 163} | 1710 {17.43, 248} | 1202 {12.26, 186}
1103 {11.24, 160} | 827 {8.43, 120} | 1310 {13.35, 190} | 979 {9.98, 142} | 1517 {15.46, 220} | 1138 {11.60, 165} | 1724 {17.57, 250} | 1289 {13.14, 187}
1110 {11.31, 161} | 834 {8.50, 121} | 1324 {13.49, 192} | 993 {10.2, 144} | 1631 {16.62, 222} | 1145 {11.67, 166} |  |

  Note

  • Use the compression pressure limit chart when comparing cylinder compression readings to determine if the lowest reading is within 75 percent of the highest reading.
  Example :
After measuring the compression pressure of all cylinders, if maximum reading is 1351 kPa {13.77 kgf/cm 2, 196 psi} and minimum reading is 1069 kPa {10.89 kgf/cm 2, 155 psi}, engine condition is within the specification and compression is normal.

10. Remove the compression gauge.

11. Connect the ignition coil connector.

12. Install the spark plugs.

Tightening torque

  9-20 N·m {91-204 kgf·cm, 79-177 in·lbf}

13. Install the ignition coils. (See IGNITION COIL REMOVAL/INSTALLATION [AJ].)

14. Install the fuel pump relay.