Mechanical Inspection: Compression
NOTE:
Manufacturer does not provide a compression specification (psi). Manufacturer identifies if compression pressure difference between cylinders is 25 percent or less, compression pressure is acceptable.
Release fuel system pressure. See FUEL PRESSURE RELEASE under FUEL SYSTEM. Install a remote starter switch to starter circuit. Remove spark plugs and install a compression gauge. Crank engine a minimum of 5 strokes and record highest compression reading. See COMPRESSION SPECIFICATIONS table.
COMPRESSION SPECIFICATIONS
| Application | Specification | ||||
|---|---|---|---|---|---|
| Compression Ratio | |||||
| S-Type | |||||
| 3.0L | 10.5:1 | ||||
| 4.0L | 10.75:1 | ||||
| XJR, XJ8 & XK8 | |||||
| Normally Aspirated | 10.75:1 | ||||
| Supercharged | 9.0:1 | ||||
| Compression Pressure | (1) | ||||
| Maximum Variation Between Cylinders | 25% | ||||
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