How could ULSD cause fuel pump failure?
– Both biodiesel and the old petroleum diesel cause pump seals to swell, but ULSD causes the seals to shrink. If the seals shrink enough, the fuel pump will leak fuel and/or suck in air. The symptom of pump failure in the TDIs has been not being able to start the car because there is air in the lines that got in through the leaky seals. Even Chevron acknowledges that ULSD can cause seals to fail: Click here to read Chevron’s statement Lubricity – In addition, ULSD is lower in lubricity. Most fuel pumps use the fuel for lubrication and may burn out on fuel with low lubricity. Biodiesel is very high in lubricity and good for your fuel pump and engine life. Recommendation – Run blends of at least 20-30% biodiesel – To prevent pump damage, try to run a blend of at least 20-30% biodiesel at all times. The biodiesel will add lubricity and help prevent the seals from shrinking/leaking.
