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
During compression test, engine must be at normal operating temperature, all spark plugs removed and throttle (and choke) valve must be in WOT position. See COMPRESSION SPECIFICATIONS table. Crank engine through 4 or more compression strokes.
| Application | Specification | |||||
|---|---|---|---|---|---|---|
| Compression Ratio | ||||||
| 4.1L (VIN 7 & 8) | 9.0:1 | |||||
| 5.0L (VIN F) TPI | 9.5:1 | |||||
| 5.0L (VIN G & H) 4-Bbl. | 9.3:1 | |||||
| 5.0L (VIN Y & 9) 4-Bbl. | 8.0:1 | |||||
| 5.7L (VIN 6) 4-Bbl. (1) | 8.2:1 | |||||
| 5.7L (VIN 8) TPI | (2) 9.5:1 | |||||
| Compression Pressure | ||||||
| 4.1L | 140-165 (9.8-11.6 kg/cm2 ) | |||||
| All Others (Min.) | 100 psi (7.0 kg/cm2 ) | |||||
| Max. Variation Between Cylinders | 30% | |||||
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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.