LINES GP-POWER TRAIN OIL 3984487 - Caterpillar

Use of two wrenches on fuel line nuts.--------------- END SUPPLEMENT ---------------Two wrenches must be used to loosen or tighten line nuts on the fuel injection nozzle assemblies in 3306 Vehicular Engines with direct injection fuel systems which are used on some 3306 Vehicular Engines etc. Use one wrench to hold the nozzle adapter while the other wrench is used to loosen or tighten the line nut. This will prevent stresses which can damage the fuel injection nozzle assembly. Never loosen or tighten a line nut without a second wrench on the nozzle adapter.
Service Manuals for these engines will have a note, which reads as follows:
When fuel injection lines are loosened or tightened on the fuel injection nozzles, two wrenches must be used. The nozzle must be held with a wrench or damage to the nozzle can result.
Use of two wrenches on fuel line nuts.