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.
Mechanical Inspection: Compression
Ensure battery is fully charged. Warm engine to normal operating temperature. Disconnect wire at ignition coil to prevent engine from starting. Check engine compression with all spark plugs removed and throttle wide open.
Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions.
| Application | Specification | ||||
|---|---|---|---|---|---|
| Compression Ratio | |||||
| Ram Pickup (8.0L) | 8.4:1 | ||||
| All Others | 9.1:1 | ||||
| Normal Compression Pressure | (1) | ||||
| Minimum Compression Pressure | |||||
| Dakota | |||||
| 2.5L | (1) | ||||
| 3.9L, 5.2L & 5.9L | 100 psi (690 kPa) | ||||
| Durango | 100 psi (690 kPa) | ||||
| Ram Pickup | 100 psi (690 kPa) | ||||
| Ram Van Ram Wagon | 100 psi (690 kPa) | ||||
| Maximum Variation Between Cylinders | (1) | ||||
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NO RELATED
Use the Manual With the Right Hardware
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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.