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
Check engine compression with engine at normal operating temperature at specified cranking speed with all spark plugs removed and throttle wide open. Release fuel pressure. To release fuel pressure, remove fuel pump fuse (located in fuse block) and start engine until it stalls. Crank engine 2-3 times to release residual pressure.
On Q45 with Direct Ignition System (DIS), remove ornament cover and disconnect harness connector between ignition coil and power transistor.
On all models, crank engine at least 6 revolutions to determine engine compression. Compression reading should be as specified. See ENGINE COMPRESSION table.
| Standard psi (kg/cm2 ) | Minimum psi (kg/cm2 ) | RPM |
|---|---|---|
| 185 (13.0) | 142 (9.8) | 300 |
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.
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