Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Engine Compression
Prior to checking compression, be sure batteries are fully charged. During compression check, crank engine with ignition off through at least 6 compression strokes and note number of strokes required to obtain highest reading. Repeat check on each cylinder, cranking engine same number of compression strokes. DO NOT add oil to cylinder. Adding oil may cause hydrostatic lock and extensive engine damage. Maximum variation between cylinders on 6.9L should not exceed 25%.
- Start and warm engine to normal operating temperature. Turn ignition off. Remove air cleaner and/or intake opening cover. Disconnect injection pump solenoid leads (fuel cutoff solenoid leads on 2.2L). On 2.2L engine, disconnect glow plug harness (Blue/Red stripe wire) from engine wiring harness.
- On all models, remove all glow plugs and insert compression gauge in No. 1 cylinder glow plug hole. Crank engine (ignition off on 6.9L engine) and note compression reading. Repeat compression test.
| Application | Specification |
|---|---|
| Compression Ratio | 21.0:1 |
| Compression Pressure | 384-340 psi (26.9-23.9 kg/cm2 ) |
| Maximum Pressure Variation | 43 psi (3.0 kg/cm2 ) |
| Application | Specification | |||
|---|---|---|---|---|
| Compression Ratio | 20.7:1 | |||
| Maximum Pressure Variation (1) | ||||
| 260 psi (18.3 kg/cm2 ) | 195 psi (13.7 kg/cm2 ) | |||
| 280 psi (19.7 kg/cm2 ) | 210 psi (14.8 kg/cm2 ) | |||
| 300 psi (21.0 kg/cm2 ) | 225 psi (15.8 kg/cm2 ) | |||
| 320 psi (22.5 kg/cm2 ) | 240 psi (16.9 kg/cm2 ) | |||
| 340 psi (23.9 kg/cm2 ) | 255 psi (17.9 kg/cm2 ) | |||
| 360 psi (25.3 kg/cm2 ) | 270 psi (18.9 kg/cm2 ) | |||
| 380 psi (26.7 kg/cm2 ) | 285 psi (20.0 kg/cm2 ) | |||
| 400 psi (28.1 kg/cm2 ) | 300 psi (21.0 kg/cm2 ) | |||
| 420 psi (29.5 kg/cm2 ) | 315 psi (22.1 kg/cm2 ) | |||
| 440 psi (30.9 kg/cm2 ) | 330 psi (23.2 kg/cm2 ) | |||
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NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.