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.
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HOMESERVICE MANUALSCHEVROLET1987SUBURBAN R20, 7.4 N, 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEADJUSTMENTTUNE-UP - DIESELADJUSTMENTSINJECTION NOZZLESOPENING PRESSURE TEST
1987 Chevrolet Suburban R20, 7.4 N, 400/M40
Opening Pressure Test
1987 Chevrolet Suburban R20, 7.4 N, 400/M40SECTION Opening Pressure Test
- Using a nozzle tester and Test Oil (ISO 4113) at room temperature, check opening pressure. Connect test line to nozzle holder assembly and tighten fittings.
- Close shutoff valve at pressure gauge and operate tester handle sharply several times. Check for proper nozzle position. Spray should be injected into a clean container.
- Open shutoff valve at pressure gauge 1/4 turn. Operate tester handle slowly to determine injection opening pressure. Observe gauge reading just before oil is sprayed from tip. Minimum opening pressure is 1500 psi (105 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.