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 at cranking speed with engine at normal operating temperature, all glow plugs removed and throttle wide open. Ensure crankcase is full and oil is correct viscosity. Ensure that battery is fully charged. Remove air cleaner (or intake manifold cover). Mark and disconnect injection pump solenoid leads from injection pump. With compression gauge installed, use remote starter 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. See COMPRESSION TEST PRESSURE for appropriate readings.
| Highest Cylinder psi (kg/cm2 ) | Lowest Cylinder psi (kg/cm2 ) |
|---|---|
| 260 (18.3) | 195 (13.7) |
| 280 (19.7) | 210 (14.8) |
| 300 (21.1) | 225 (15.8) |
| 320 (22.5) | 240 (16.9) |
| 340 (23.9) | 255 (17.9) |
| 360 (25.3) | 270 (19.0) |
| 380 (26.7) | 285 (20.0) |
| 400 (28.1) | 300 (21.1) |
| 420 (29.5) | 315 (22.1) |
| 440 (30.9) | 330 (23.2) |
| Application | Compression Ratio |
|---|---|
| 7.3L (Diesel) | 21.5:1 |
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.