Biodiesel and rubber bits

[the careful driver]

Hi there

I have a little technical knowledge, but not much.

I am trying to get my head around the possible rubber components used in the internal fuel supply system of an engine. Can anyone help?

What this is about is 100% biodiesel.

Apparently 100 biodiesel contains a fraction of methanol, 0.1%, but this is enough to rot rubber components over time if you are using only B100 100% biodiesel.

You can avoid these problems by identifying the possible parts of your fuel system which could be made from rubber, and replacing them with Viton, or some similar material.

Can anyone help me how I can find out what parts of my fuel system might be made from rubber?

This could be :

Rubber connecting hoses
Gaskets in the system, (how many are there?)
O-rings, which are I suppose gaskets (?)
Anything else you can think of ? !

I understand that many parts of cars made in the last 10 years are actually made from rot-resistant material, but it is not very clear which ones.

Thanks for any help !

Peter

[kitesurf_phil]

I can't swear to it, but from what I have been told, none of the bits on the Surf are natural rubber. Morr has been running on biodiesel (WVO) for a couple of years without anything perishing.

[Morr]

I run on SVO/Diesel mix, this is straight vegetable oil mixed with diesel. WVO is waste vegetable oil, neither of these will generally attack natural rubber products. Biodiesel is a different matter, it is made by a chemical process using vegetable oil (new or waste, doesn't matter) and either methanol or ethanol. The methanol method is the most common. There are also catalysts involved, but the end product is essentially comprised of the combined oil and methanol.
Ideally there should not be any free methanol content in the finished product, good quality biodiesel will have undergone a methanol recovery process.
I'm not sure as to whether any remaining methanol will attack natural rubber, but the biodiesel itself will anyway.
The biodiesel is naturally a mild solvent (it dissolves regular diesel well enough to be used to help clean up oil spillages at sea) and will attack natural rubber compounds. These are no longer found in modern fuel systems, have been replaced with synthetic compounds, of which Viton is a popular example. It is generally accepted that all diesels since the early/mid '90's do not have any rubber in their systems (it was removed for a reason that escapes me at present), some diesels had phased out its use long before this.
I cannot say with 100% certainty, but strongly believe that the Toyota diesels had removed all natural rubber from the fuel systems somewhat earlier and should be perfectly OK using any percentage up to and including 100% Biodiesel.
Remember that its natural solvent properties may well lift sludge from the bottom of your tank leading to a blocked fuel filter, carry a spare just in case, and change it anyway, regardless of mileage, about 6 months after starting to use high ratios of biodiesel.

[the careful driver]

Thanks for your input

I had been reading that one of the 1999 Mercedes had a fuel injector failure, I think it was something like that anyway, due to a rubber O-ring. Something like that, a late model anyway.

I suppose some of the other things it might attack like adhesives or gums will only come to light through useage. If you have heard that they put non-rubber replacement parts in though that is a positive thing.

Thanks !

Peter