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
Check engine compression with engine at normal operating temperature, all spark plugs removed (on dual plugs, remove exhaust side only), and throttle wide open. Ensure crankcase is full and oil is of correct viscosity. With compression gauge installed, use remote starter switch to crank engine. Crank engine at least 5 revolutions, and record highest reading. Repeat procedure for all cylinders, using approximately same number of revolutions. Lowest compression reading should not be less than 75 percent of highest compression reading. No cylinder compression reading should be less than 100 psi (7 kg/cm2 ).
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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.