Just hit me, forgive me if this was mentioned in the individual threads- could the O-ring failure (swelling) be because this o-ring in this pump (or maybe just some lots) is susceptible to swelling from ethanol?
The swelling might even be the cause of the tab cracking.
i was wondering the same thing. I think I can answer this and give us a test that would prove one way or the other.
Mine failed, one partially cracked tab and the oring squished out. I fitted a new oring with the cap that had broken tabs. It lasted a bit over 200 miles and failed again. i had an extra oring and hose clamps to hold the cap on just in case so i got it back on the road easily until I located a good used cap. here's the key:
***when i removed the "new" oring (one day old and 200 miles) it looked exactly like the old one that had failed - waaaay stretched out. it was not even close to reusable.
so this tells us that whatever is causing it can happen very quickly.
but i don't think it's ethanol.
given that it happened so fast on mine that gives us a very easy test. simply place an oring in ethanol gasoline and see how it does after one day. you can even stretch it over a can or something to give it some tension (easier than trying to find compression).
but i think that's highly unlikely to be the case so i'm not doing the test.
i just got a cap from a board member and he happened to include the original old oring and it looks perfectly sized - though aged, not stretched at all. i highly doubt it avoided ethanol gasoline the past 10 years and who knows how many miles before hitting the junk heap.
based on my experience i think the tabs crack and then the ensuing pressure relief from the cap sealing surface and fuel pressure is enough to slowly push the oring out from under the cap...a little bit, then some more, etc. until it's hanging out and the car won't run.
the key is the orings are *really* stretched out....
i'd be curious to know why the caps are cracking....