COMPRESSION INSPECTION [AJ (3.0L Duratec)]
id0110a3800300
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Warning
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• Hot engines can cause severe burns. Be careful not to burn yourself during removal/installation of each component.
1. Verify that the battery is fully charged. (See BATTERY REMOVAL/INSTALLATION [L3, AJ (3.0L Duratec)].)
2. Warm up the engine.
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Warning
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• Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
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• Fuel line spills and leakage from the pressurized fuel system are dangerous. Fuel can also irritate skin and eyes. To prevent this, before perfroming the fuel pump unit removal/installation, always complete the Fuel Leakage Inspection, and remove the fuel pump relay. (See BEFORE SERVICE PRECAUTION [AJ (3.0L Duratec)].)
3. Stop the engine and allow approx. 10 min for the exhaust system to cool down.
4. Disconnect the ignition coil connector. (See IGNITION SWITCH REMOVAL/INSTALLATION.)
5. Remove all the spark plugs.
6. Measure the compression pressure using the following procedure.
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(1) Connect the compression gauge into the spark plug hole.
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(2) Crank the engine a minimum of five compression strokes and record the highest reading.
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Note
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• Note the approximate number of compression strokes required to obtain the highest reading.
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(3) Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.
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(4) 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.
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• 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.
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- If the pressure increases by adding the engine oil, the piston ring or the the cylinder surface is worn, or they are damaged. Perform overhaul servicing.
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- If the pressure does not increase, valve seizure, valve attachment failure, or pressure leaking from the cylinder head gasket might be occurring. Perform overhaul servicing. If the compression stays low, a valve may be struck or improperly seasted and timing chain inspection is required.
Compression Pressure Limit Chart
kPa {kgf/cm2, psi}
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Maximum pressure
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Minimum pressure
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Maximum pressure
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Minimum pressure
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Maximum pressure
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Minimum pressure
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Maximum pressure
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Minimum pressure
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924
{9.41, 134}
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696
{7.10, 101}
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1131
{11.52, 164}
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848
{8.65, 123}
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1338
{13.63, 194}
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1000
{10.20, 146}
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1544
{15.73, 224}
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1158
{11.81, 168}
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938
{9.56, 136}
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703
{7.17, 102}
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1145
{11.67, 166}
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855
{8.72, 124}
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1351
{13.77, 196}
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1014
{10.34, 147}
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1558
{15.88, 226}
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1165
{11.88, 169}
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952
{9.70, 138}
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717
{7.31, 104}
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1158
{11.80, 168}
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869
{8.86, 126}
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1365
{13.91, 198}
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1020
{10.40, 148}
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1572
{16.02, 228}
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1179
{12.02, 171}
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965
{9.83, 140}
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724
{7.38, 106}
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1172
{11.94, 170}
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876
{8.93, 127}
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1379
{14.05, 200}
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1034
{10.54, 150}
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1586
{16.16, 230}
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1186
{12.09, 172}
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979
{9.97, 142}
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738
{7.53, 107}
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1186
{12.08, 172}
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889
{9.07, 129}
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1303
{13.28, 202}
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1041
{10.62, 151}
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1600
{16.30, 232}
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1200
{12.24, 174}
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933
{9.51, 144}
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745
{7.60, 109}
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1200
{12.23, 174}
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903
{9.21, 131}
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1407
{14.34, 204}
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1055
{10.76, 153}
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1055
{10.75, 153}
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1207
{12.31, 175}
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1007
{10.26, 146}
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758
{7.73, 110}
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1214
{12.37, 176}
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910
{9.28, 132}
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1420
{14.47, 206}
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1062
{10.83, 154}
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1627
{16.58, 154}
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1220
{12.44, 177}
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1020
{10.39, 148}
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765
{7.80, 111}
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1227
{12.50, 178}
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917
{9.35, 133}
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1434
{14.61, 208}
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1075
{10.96, 156}
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1641
{16.72, 238}
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1227
{12.51, 178}
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1034
{10.54, 150}
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779
{7.94, 113}
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1241
{12.65, 180}
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931
{9.49, 135}
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1448
{14.76, 210}
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1083
{10.04, 157}
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1655
{16.87, 240}
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1241
{12.65, 180}
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1048
{10.68, 152}
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786
{8.02, 114}
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1255
{12.79, 182}
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936
{9.54, 136}
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1462
{14.90, 212}
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1089
{11.10, 158}
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1669
{17.01, 242}
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1248
{12.73, 181}
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1062
{10.82, 154}
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793
{8.09, 115}
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1269
{12.93, 184}
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952
{9.70, 138}
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1476
{15.04, 214}
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1103
{11.25, 160}
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1682
{17.14, 244}
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1262
{12.87, 183}
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1076
{10.96, 156}
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807
{8.23, 117,}
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1282
{13.06, 186}
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965
{9.84, 140}
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1489
{15.17, 216}
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1117
{11.39, 162}
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1696
{17.28, 246}
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1269
{12.94, 184}
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1089
{11.10, 158}
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814
{8.30, 118}
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1296
{13.21, 188}
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972
{9.91, 141}
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1503
{15.32, 218}
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1124
{11.46, 163}
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1710
{17.43, 248}
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1202
{12.26, 186}
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1103
{11.24, 160}
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827
{8.43, 120}
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1310
{13.35, 190}
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979
{9.98, 142}
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1517
{15.46, 220}
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1138
{11.60, 165}
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1724
{17.57, 250}
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1289
{13.14, 187}
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1110
{11.31, 161}
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834
{8.50, 121}
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1324
{13.49, 192}
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993
{10.2, 144}
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1631
{16.62, 222}
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1145
{11.67, 166}
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Note
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• After measuring the compression pressure of all cylinders, if maximum reading is 1,351 kPa {13.77kgf/cm2, 196psi} and minimum reading is 1,069 kPa {10.89kgf/cm2, 227psi} the engine condition is within the specification and compression is normal.
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Standard
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1,565 kPa {15.96kgf/cm2, 227psi}[210 rpm]
7. Install the fuel pump relay.
8. Install the spark plugs.
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Tightening torque
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9-20 N·m {91-203 kgf·cm, 79-177 in·lbf}
9. Install the ignition coils. (See IGNITION COIL REMOVAL/INSTALLATION [AJ (3.0L Duratec)].)