The 50 post rule exists to try and protect members from scams that plague both buyers and sellers.
Without it posting a vehicle for sale here would be no different than the open market. It's far from perfect but it's what we have.
The OP has asked for advice about how to protect themselves...
You most likely have a leak between the tank and pump. Because it's under negative pressure as the pump 'sucks' fuel leakage is minimal but air can be pulled in.
Inspect from pickup pipe all along fuel line or replace
I've taken out 3 barrow loads of discarded dummies and Accy has swept up the empty tinnies and jumped up and down on them...
Should be a bit more space now and hopefully the disc will stop burping.