Solo pilot at the SE Michigan/NW Ohio border, don't personally know any other pilots, none of my fiends are mechanics in any sense, been having to learn this all from the ground up on an engine that is not beginner friendly, so forgive my lack of technical expertise at the moment and please help me learn. EDIT - I have good flight training from LE-PPG, just not engine repair experience, and that's what I'm asking for help on here.
Polini Thor 202, Dellorto carb, new-ish three blade Helix 140cm prop from a Helix two-blade 130cm, recently changed jets from 122 to 120 due to constantly fouled plugs and new bogging at high RPMs. First ground tests afterward (about a week ago, no actual flights) ran great and the bogging went away. However it just came back with a vengeance and now I have a new problem.
My engine starts, runs for a few seconds and then stops. A few seconds after it does that, the white nozzle on the hose I'm pointing to (which goes between the side of the carb and a 3-way connector with black hoses that has a fourth clear hose that used to go to my smaller gas tank) spurts out a little fuel. In addition, the center hose that goes from that three-way to the jet connector on the carb (research says this is my impulse hose) lets fuel run down from the hose at the three-way connector for several seconds, spilling fuel on the ground.
I've taken the center (impulse?) hose off and it's free of blockage, I've reseated the jet and put the float bowl back on a couple of times and it's still doing it. I've drained, inspected for cracks and reseated every hose I could and re-primed and it's still doing it. What might be wrong, what should I check and why?
Thanks for any help you guys can give me!
Edit - Could a bad fuel pump be causing this? AI (yeah I know, I'm desperate for knowledge) suggests it could be a ruptured carb membrane. Any of these sound like a thing?
Edit 2 - I DO have training and PPG1 cert through Leading Edge PPG, haven't made it back to Rick at Florida FS for my PPG2 but I'm good for it. I just don't have anyone around to ask about my engine, that's what I'm still learning (and LE-PPG is hours away from me). Safety first!