COMPRESSION INSPECTION[AJ (3.0L Duratec)]

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Warning
•  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[AJ (3.0L Duratec)].)

2.  Warm up the engine.

Warning
•  Fuel vapor is hazardous. It can very easily ignite, causing serious injury and damage. Always keep sparks and flames away from fuel.
•  Fuel line spills and leakage from the pressurized fuel system are dangerous. Fuel can also irritate skin and eyes. To prevent this, before performing 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 COIL REMOVAL/INSTALLATION[AJ (3.0L Duratec)].)

5.  Remove all the spark plugs. (See SPARK PLUG REMOVAL/INSTALLATION[AJ (3.0L Duratec)].)

6.  Measure the compression pressure using the following procedure.

(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.
Note
•  Note the approximate number of compression strokes required to obtain 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 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 pressure increases by adding the engine oil, the piston ring or the cylinder surface is worn, or they are damaged. Perform overhaul servicing.
―  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 seated and timing chain inspection is required.

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
•  After measuring the compression pressure of all cylinders, if maximum reading is 1,351 kPa {13.77 kgf/cm2, 196 psi} and minimum reading is 1,069 kPa {10.89 kgf/cm2, 227 psi} the engine condition is within the specification and compression is normal.
Standard
1,480 kPa {15.10 kgf/cm2, 215 psi}[210 rpm]

7.  Install the fuel pump relay.

8.  Install the spark plugs. (See SPARK PLUG REMOVAL/INSTALLATION[AJ (3.0L Duratec)].)

9.  Install the ignition coils. (See IGNITION COIL REMOVAL/INSTALLATION[AJ (3.0L Duratec)].)