I’m facing an unusual problem and could use some feedback. I tore down my carb for a good cleaning. Checked the jets, put the dismantled carb in the ultrasonic cleaner, inspected everything, set float level to 0.860”, and reassembled. After reinstalling, the engine ran pig rich and the catch cab started filling up with fuel. Took the carb part again, check the float needle for wear and and debris in the bowl. Found everything looking good, tried again, same issue. I then started raising the float height until the issue stopped and the engine ran properly per spark plug inspection, but now the float level is 0.890”. The engine seems to run strong at WOT, put part throttle it still runs rich, so much so that the slide needle is all the way down (clip on uppermost position). Tried a new float and needle, same issue.
I’m stumped as to why this happened after a thorough cleaning, and why the carb needs such a high float position. The only thing I could think of is perhaps the fuel pump is outputting too much pressure and it happened coincidentally?
I would be suspicious that the float and needle are suspect. Tough to say where, but it seems like the fuel isn’t shutting off the flow properly (explaining why the catch can is filling up). Make sure the needle is in the correct position and is actually shutting off the flow when it is in the closed position.
So I did that using some fuel in a funnel, but that got me thinking of the fuel pump is suspect and is pumping out too much pressure. I’m unsure if that’s at all possible, though.
I don’t think that is likely but you can try a new pump. It might benefit to watch this video and see if you missed something or if your placements of the needle matches up.
If the bowl is overflowing, then you have something keeping the needle open. Now to diagnose and find it.
The fuel pump is NOT the issue. The needle valve should close and cut off fuel coming into the bowl when the floats are up. If the bowl is overflowing, then something it catching, or bent, or not seating fully.
I can pressurize the fuel tank and push fuel from the tank through the pump and into the bowl, right up until the bowl fills, then the float goes up and valve closes, no more fuel can flow. Its how I would prime the fuel system every time we tore down the Briggs…
Have had floats that got stuck because I bent them, misadjusted them, and on 1 occasion a casting issue on the carb. Usually it was something I did mishandling the float assembly while servicing that caused my issues.
Even though you used the ultrasonic cleaner, I’d still use carb cleaner in every hole and jet, spraying through. Disassemble again and spray everything. I’m not 100% sold on the ultrasonic cleaner doing a good enough job.
Did you replace the needle? The needle is what cuts off the fuel flow and stops the overflow to the catch can. It could be messed up a little and not seating properly. Take the bowl off and see how much the needle drops out of the hole. If it comes down a lot out of the hole I bet you need to bend the tab the needle sits on up towards the carb. It might be coming out too far and then gets on an angle trying to come back up to close and binds up. There is a float drop measurement, but I don’t remember what it is off hand. Like Chuck said something is binding or sticking and not letting the floats rise to close the needle seat. The only fuel pump issue would be if it isn’t pumping enough fuel. It can’t over pump gas to the bowl. That is the job of the floats and needle to stop the flow of gas.
I carefully inspected the old float needle and didn’t see any damage. I replaced it and have the same issue. One thing I haven’t checked (doh!) is float drop - I’ll do that next.