New gas on old parts

[Bruce Parker (RIP)]

I've heard a lot about the effects of new ethanol gas on old rubber parts but experienced it for the first time. My GMC fuel pump was NOS and I've run it without trouble for several years until now. It still pumps at slow speeds but breaks down after that. Taking it off, I see the reason is because the main diaphragm has gone soft. Compared to a new pump its performance is very weak. I've put on a new pump from the same batch as the dead one and I've been using only high test gas lately (which they tell me is the only ethanol free gas available here in Canada) so we'll see how long it lasts.