The rubber inside is unlikely to have any ethanol resistance, whatsoever. However, I am increasingly skeptical that modern rubber is really any better. In many cases, it’s much worse.
I’d be tempted to run it and see what happens.
I have had decent luck with NOS rubber stuff in other parts of my truck. I’ve yet to try anything that touches fuel, however.
Wonder if you could buy a new diaphragm without a whole new rebuild kit?
