Erratic engine - air in the system or fuel?

[slawosz]

My engine is quite erratic - I know I have fuel bug or whatever is left as used marine 16. I changed the filter after around 8 hours after previous change but didnt help this time. I bled the engine only using screw on governor - normally that worked. I wonder if there is possibilty that little air is in the system that causes erratic behaviour? Or maybe its filter again - maybe marine 16 did good job and lot of debris on the fuel…

 

[Minerva]

As a very loose rule of thumb, if the engine fails quite quickly it will likely be an issue with air in the fuel line. If it dies over a couple of seconds it's likely from fuel starvation.

Best to work from first principles; change the filter and bleed from every bleed point from the tank to the injectors in turn.

 

[Tranona]

Double check the sealing ring for the fuel filter at the rear of the engine is properly seated. Well known problem as it is tricky to keep the bowl square when you tighten it up and there can be a little kink in the seal. Guess how I found out on my 1GM

 

[slawosz]

Double check the sealing ring for the fuel filter at the rear of the engine is properly seated. Well known problem as it is tricky to keep the bowl square when you tighten it up and there can be a little kink in the seal. Guess how I found out on my 1GM

But is it possible that engine would work rough but for hours with this issue?

 

[Tranona]

Yes, tiny amount of air entering the fuel would give those symptoms. You can check when you check the filter and clean/change. Also suggest you bleed right to the injector.

 

[pioneer]

If the spill pipe is returned to the off engine filter and not the tank any air can recirculate no matter how much you bleed it. Reverse/return bleeding can remove the air, don't ask how i know!!

 

[2Tizwoz]

Steel suction pipe, out of sight in the tank, can corrode and let air in.