Do you have a brass float, if not get one! I would rebuild the carb and original fuel pump and get rid of the electric they can be headaches or cause big issues. I have a tractor I just got in that I was told ran real rough loading on the trailer and was leaking oil. I seen the electric pump and figured right away what was going one. Well none the less drained 1gal plus of oil/gas out of the crankcase (only holds a couple quarts.) The electric pump was flooding the carb and then flooded the crank case. I know your is opposite as its a float and needle valve issue but this could happen too. Luckily they only ran it 1 min to load it on a trailer but if ran longer could have wiped out a motor or cause a fire etc. Onans are awesome engines if set up correct.Where are you located?