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Home >> GMC >> 1989 >> Forward Control 3.9 L, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - Diesel >> Operation >> Injection Nozzles
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Injection Nozzles

Each of the 8 combustion chambers is equipped with an injection nozzle. The injection nozzle has a single fuel inlet fitting and 2 fuel return fittings, (one on each side of fuel inlet fitting). The nozzle is threaded into the cylinder head. Injection nozzles are spring loaded and calibrated to open at a specified fuel line pressure. The combustion chamber end of the nozzle has a replaceable compression seal and carbon stop seal.