Elastomer compatibility fuel testing

Prescott, AZ
If you check the link below you will find a report of using standard sized o-rings for testing diesel fuel blends that contain various amounts of solvents. Particularly at the specific link you will find that ULSD, which is normal pump diesel fuel available in the USA at any gas station that sells diesel fuel, damages silicon seals.
Elastomer compatibility fuel testing

It just so happens that old injection pumps, especially the Roosa Master Stanadyne DB-2 and DS-5 injection pumps found on 6.2L and 6.5L diesel engines, have silicone seals on them. This means if you are running an old military diesel vehicle on ULSD, then your IP will not last more than a year.

I have contacted Stanadyne and informed them of this problem. They have not contacted me regarding a solution to the problem.

You can find seal kits for Roosa Master / Stanadyne Diesel Injection Pump Seal Kit 24370 Db2 at this link.

It comes with a collection of seals made for a several elastomers. The critical seals are the 3 cup-shaped ones that fit onto the drive shaft of the hydraulic head, which are responsible for generating pop pressure of the fuel being delivered to the injectors, which is about 1,500 PSI. Each kit comes with 2 cup-shaped seals that are made from BUNA-n, and 1 silicon seal. The BUNA-n seals do not seem to have a significant problem with ULSD. So, you can purchase 3 kits to to rebuild 2 pumps by replacing the silicone seal for one of the BUNA-n seals in the third kit.

Another solution to this silicone seal incompatibility with ULSD is to blend your own DIY diesel fuel that contains no more than ULSD at 50%.

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