STEP AS 1696712 - Caterpillar

Introduction
There have been instances of issues with DEF pumps. After analysis, the cause of the issues has been found as contamination with hydrocarbons.Note: Diesel fuel is an example of a hydrocarbon.The DEF filter is equipped with a compensator located in the center of the filter assembly. If the compensator comes into contact with hydrocarbons, the compensator will swell and is designed to block the filter assembly and protect the DEF pump.Solution
The following procedure is designed to diagnose if the DEF pump has been contaminated with hydrocarbons.
Do not operate or work on this product unless you have read and understood the instruction and warnings in the relevant Operation and Maintenance Manuals and relevant service literature. Failure to follow the instructions or heed the warnings could result in injury or death. Proper care is your responsibility.
Ensure that the engine is stopped before any servicing or repair is performed. The Diesel Exhaust Fluid (DEF) system must have completed a proper shutdown. Service on the DEF pump prior to completion of a proper shutdown can result in DEF spray and spillage.
Do not turn off the battery disconnect switch until the indicator lamp has turned off. If the switch is turned off when the indicator lamp is illuminated, the Diesel Exhaust Fluid (DEF) system may not shut down properly. If the DEF system does not shut down properly, DEF could freeze and damage the pump and lines.
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Cat Dealer Service Tool Catalog" or refer to Special Publication, PECJ0003, "Cat Shop Supplies and Tools Catalog" for tools and supplies suitable to collect and contain fluids on Cat products.Dispose of all fluids according to local regulations and mandates.
Note: Clean water should be used to wash spilled DEF off machine components and surfaces.Note: Wear gloves when handling the DEF filter.
Illustration 1 g06278274
(1) Protective cover
Remove protective cover (1).
Illustration 2 g06278289
(2) DEF filter cap
Use a suitable tool to remove DEF filter cap (2).
Illustration 3 g06278325
(3) Compensator
With the filter installed in the DEF pump, carefully remove compensator (3).
Illustration 4 g06278356
(A) 38 mm (1.5 inch)
(B) 97 mm (3.8 inch)
Check the measurements of compensator (3). Check if the measurements are greater than specified in Illustration 4. This condition indicates that the DEF pump is contaminated with hydrocarbons.
If the measurements indicate contamination, replace the DEF pump filter. Refer to Operation and Maintenance Manual, Diesel Exhaust Fluid Filter - Replace.Flush the DEF tank. Refer to Systems Operation, Testing and Adjusting, Diesel Exhaust Fluid Tank - Flush.
If the measurements are within the specification, continue to follow the appropriate troubleshooting procedure to determine if the DEF pump has a fault.