1983/02/16 Caterpillar

All 3500 Series Engines

Before unit injectors are removed from 3500 Series Engines, it is very important to disconnect the fuel supply and return lines from the cylinder heads. Caps must then be installed on the end of the lines to prevent fuel leakage into the combustion cylinders. See the illustration. If too much fuel leaks into a cylinder, a hydraulic lock will form when the piston moves up during engine start-up. The hydraulic force can be large enough to crack the cylinder head spacer plate.