Roger L. Leisenring, Jr.Roger L. Leisenring, Jr.Sunoco, Inc.Sunoco, Inc.

Fuel Quality SpecialistFuel Quality Specialist

Chairman ASTM Diesel Fuel Section (D975)Co-Chairman NCWM Premium Diesel fuelPast Chairman SAE Diesel FuelPast member of California Diesel Fuel Advisory Task Force

October 1, 1993October 1, 1993Introduction of Low Sulfur Diesel FuelIntroduction of Low Sulfur Diesel Fuel

Governor Pete Wilson California created

Diesel Fuel Advisory Committee Investigated Lubricity Investigated reported seal leakage

Seal Leakage Occurred BecauseSeal Leakage Occurred Because

Reduced elasticity due to age, old Typically high mileage, or hours Exposure to high temperature Thermal cycle Reduced swelling (or shrinkage)

Fuel related problems affected a relatively small percentage of the overall vehicle population; however, the problems are serious for the owners of the vehicles involved

Diesel Fuel Task Force 2/9/04

Seal Leakage PopulationSeal Leakage Population

Fuel system leakage were from seals made of nitrile, or Buna N, rubber. Seals made of fluorocarbon, Viton, did not experience seal failures.

Seal Material ConclusionSeal Material Conclusion

Lubricity was not the cause of pump leakage. However, a minimum 3000 g

SLBOCLE was specified to assure

adequate lubricity while the ASTM, ISO, SAE and CEC defined a test and a limit.

Lubricity ConclusionLubricity Conclusion

2005 update: Effective 1/1/05 ASTM D975 includes a lubricity specification

Oxidation of fuels form peroxides,Oxidation of fuels form peroxides,which can lead to deterioration of which can lead to deterioration of seals. An SAE report mentioned this, seals. An SAE report mentioned this, however, peroxides were low and fuels however, peroxides were low and fuels were not stored very long.were not stored very long.

PeroxidesPeroxides

Update: ASTM task force is investigating this issue

Why some Why some Aged nitrile seals might be more susceptible because old seals are less pliable and elastic. When new they change shape and fill the cavity maintaining a seal. If the seal is hardened, loss of plasticizers and have “compression set” changes in aromatics of the fuel might have an effect on sealing.

Most, if not all manufactures, responded by eliminating nitrile rubber seals and replacing with fluorocarbon seals.

Keep in mind. Not all old seals leaked, Southern California had LSD in 1985 with no reported problems. Sweden which had extremely low aromatic fuels did not experience any problems. Therefore, fuel alone was not the cause of leakage.

Replacement of the seals solved the Replacement of the seals solved the leakage problem in most cases.leakage problem in most cases.After 1994 OEMs should have advisedAfter 1994 OEMs should have advisedexisting fleets and implemented design existing fleets and implemented design changes for future models.changes for future models.

There were repeat failures, but thisThere were repeat failures, but thiswas tied to improper installation of the was tied to improper installation of the seals, and were vehicle repeat seals, and were vehicle repeat compared to component repeat compared to component repeat failures.failures.

The Fix for Seal LeakageThe Fix for Seal Leakage

CA Experiment # 4CA Experiment # 4

Objective: Determine if switching

between fuels with different seal swell

characteristics could result in leakage.

New and used fuel pumps were

operated on high and low swell fuels,

as determined by new o-ring swell test.

CA Experiment # 4CA Experiment # 4

Outcome:

1. Reconditioned pumps operated on

both high and then low swell fuels did

not leak on either fuels.

2. 2 out of 12 (16%) in-service pumps

leaked when switched from high swell to low

swell fuel. 1 was minor which did not lead to

formation of fuel droplets.

US Army Kerosene ReportUS Army Kerosene Report

GM 6.2 & 6.5L engines No excess wear Hot wear operational problems occurred

with some vehicles In all cases, operational problems were

traced back to not implementing factory recommended parts change-over as per service bulletins.

The End