TUBE 3468737 - Caterpillar

D348, D349, D353 And 3400 Series Diesel Engines Equipped With Hydraulic Fuel Ratio ControlsDuring repair of a hydraulic fuel ratio control group, all the parts except the diaphragm can be cleaned with a solvent. The current (white) and former (gray) diaphragms used in the hydraulic fuel ratio controls are made of a silicone material. These diaphragms must not come in contact with any solvents. Solvents will cause the diaphragm to swell (increase in size), lose some of its strength and possibly cause a failure of the diaphragm.
After the parts have been cleaned, it is important to thoroughly prelubricate the valve assembly and the inside of the housing that makes contact with the seal on the piston. These areas must be lubricated with clean engine oil before the parts are assembled. The oil will permit the parts to move freely when the fuel ratio control is tested after assembly.
FT1820 Assembly Fixture will make repair of fuel ratio control groups easier. The fabricated tool can be put in a vise and then the fuel ratio control fastened to the fabricated tool. The FT1820 Assembly Fixture will hold the fuel ratio control in position while it is disassembled and assembled. Drawings of FT1820 are available from your Division Service Manager.