onanov

Thanks, I will monitor, and hope it is that, as that would be a much easier fix than fitting a new dip tube.

Bit of an update. We are currently out on the boat. I filled the tank when we set off, and started to notice air in the system after about 20 hrs cruising - fuel still pretty full, maybe 1cm from bottom of the fill tube. on close inspection, I think we may have a weeping joint on the fuel line close to the tank. If we do, I am guessing that could be we here the air is getting in. 2 questions 1.Does that sound plausible 2. If air is getting In at the weeping joint, can anyone one explain why no air gets into the system when the tank is 100% full, but seems to when the tank empties just a little. thanks in advance

Thanks, sounds like a job for a pro,. But at least it sounds doable. Thanks for you help.

quite possibly. However It I remember correctly, the second take off is lower down the tank. Really just trying to find a solution that does not include fitting a new dip tube, as I suspect this may be somewhat tricky

Just a thought, but if it does turn out to be a corroded dip pipe. There is infact a second fuel outlet on the tank. Used to supply a deisel heater, but now disused. Would it be an option to use this as an alternative fuel connection for the engine? I am guessing that fitting a new dip pipe will be tricky? thoughts?

There has been an engine change. Originally a National engine - boat is about 20 years old.

Thanks for all the suggestions. I have a few things to investigate when next on thMonday boat (Friday) I will let people know how I get on and report back.

would a split in the diaphram also be consistent with the fact that that issue only occurs when the tank is > 1/2 full?

There is no priming lever. Really value your input, but the lack of a fuel leak on the pump (I would have thought that fuel would leak out if air can get in) plus the air in the filter suggests an air leak somewhere closer to the tank - As per Tony b's suggestion. My thoughts would be on the fuel pick-up. That might also explain why the symptoms only occur when the tank is getting low, and why there are no fuel leaks on the system. Next question is how to get to the fuel pick up!

I will take a photo next time I am down at the boat. In the meantime, I found this pic on line. Its a BD3, its not our engine, but the fuel pump looks V similar The boat did have a diesel heater at one time, but this has now been removed. The fuel line for this is still in place (capped off) - it came direct from the tank on a separate line.

no diesel heater No diesel heater - heating is Gas

Thanks, never know that was called a lift pump - (I am not an engineer) - yes faulty pump was my thought. However, Tony's suggestion re Air sounds V plausible too - given other symptoms - (see my post about the Fuelguard filter). Thoughts?

That sounds plausible. we have a Fuelguard filter on the system (with a glass bowl) and that tends to run with the bowl 1/2 full. Never checked whether this only happens when the tank is getting low, but it is a possibility So as you say looks like air is getting in somewhere. Question is where. we have no fuel leaks as far as we can see. It is strange as the engine runs like a dream if the talk is full, even if the fuel filter bowl is only 1/2 full

Not sure what you mean by lift pump. as far as I am aware there is only 1 pump on the system, and that is the one on the engine.

Hi, Our boat is powered by a Beta BD3 with about 4000 hrs on the clock. With a full fuel tank it runs like a dream, starts first time with no issues. However, when the fuel gets to below 1/2 a tank, the engine then gets slightly harder to start. It will start, and then die immediately. Leave it for 60 seconds & try again, and it starts no problem. Runs fine when started. Topping up the tank cures the problem. Can anyone make any suggestions what might be going on?