Wet stacking is the buildup of unburned fuel, soot, and oil in a diesel generator’s exhaust when it runs too lightly loaded to reach full operating temperature. Running at adequate load, sizing units to the load, and load-bank testing as the maker recommends help prevent it.
What causes wet stacking
Diesel engines need enough load to reach normal combustion temperature. Long runs at light load, common during no-load exercise or on oversized rental units, leave fuel unburned.
Signs to look for
Black, oily residue at exhaust joints, dripping from the stack, and heavy smoke when load is applied are common signs. Oil analysis may show fuel dilution.
Prevention and load testing
Exercise generators under load where your testing program allows, size rental units to the job, and use load-bank testing when building load is not available. Follow the engine maker’s minimum-load guidance and the requirements of your testing standard.
Check the oil after light-load running
Fuel dilution thins oil. Sample oil after long light-load periods and change it if analysis shows dilution beyond the maker’s or lab’s limits.
Frequently asked questions
Is wet stacking harmful?
It can foul injectors, exhaust components, and turbochargers and dilute the oil. Address it with load and maintenance.
What is load bank testing?
Running a generator against a temporary resistive load to bring it up to working load when building load is insufficient.
Can oil analysis detect wet stacking?
It can show fuel dilution and soot, which are common effects of light-load operation.
General maintenance information. Always follow your vehicle or equipment manufacturer’s requirements and the current product data. Questions? Email [email protected].
More on data center and critical power
ORDER THROUGH INDEPENDENT AMSOIL DEALER #30734402
Ready to order, or have a question first?
Shop AMSOIL directly with Jeff’s dealer number already attached, or open a business account. AMSOIL handles pricing, checkout, and shipping. If you contact AMSOIL another way, give them dealer number 30734402.
Prefer to talk it through? Email Jeff at [email protected] with your equipment, the fluid now in use, and your approximate volume.
Related products
Confirm the oil category, viscosity, and approvals in the engine maker’s manual for each generator before ordering. These examples are not a match for a specific engine.
