Bets BD3 Strange fuel issue

[bizzard]

1 minute ago, WotEver said:

 

When his engine began to falter he threw the van about and banging the brakes on and off trying to pick up enough fuel to get him to the nearest filling station. Towards the end he carried a 20 litre can with him.

[Tony Brooks]

If the diaphragm on that type of pump split it would either leak fuel from a tell-tale somewhere in the base or fill the sump with diesel so I would not go for a diaphragm problem as the most likely fault.

 

Running with the pump cant deliver fuel idea I have known the disk type lift pumps fail because their valves go bunged up and as the OP says he has a Fuelguard I wonder if he has had fuel/bug trouble in the past so the pump valves may be clogged.

 

He says there is no priming lever on the pump so does it have one of the diaphragm priming pumps that Beta seem to love. If so I could go with that diaphragm being pin holed.

 

I would also not rule out a dip tube problem but discounted it because of the 4000 hours. However if there has been an engine change that alters everything.

[Ex Brummie]

I had this problem 2 years ago and discovered that the clamp on the flexi hose into the lift pump was letting in air when the pump sucked. Gradually, the air would rise back into the agglomerator causing an air lock. After the fourth engine failure, I just about saw the most minimal dampness at the joint. If the fitting turns in the hose, this could be your problem. I bought some hose by the metre, a couple of jubilee clips, and ground the compression clamps off. The old hose had very fine cracks under the compression clamp. Spare hose and jubilee clips are now part of my spares kit.

[onanov]

1 hour ago, Tony Brooks said:

If the diaphragm on that type of pump split it would either leak fuel from a tell-tale somewhere in the base or fill the sump with diesel so I would not go for a diaphragm problem as the most likely fault.

 

Running with the pump cant deliver fuel idea I have known the disk type lift pumps fail because their valves go bunged up and as the OP says he has a Fuelguard I wonder if he has had fuel/bug trouble in the past so the pump valves may be clogged.

 

He says there is no priming lever on the pump so does it have one of the diaphragm priming pumps that Beta seem to love. If so I could go with that diaphragm being pin holed.

 

I would also not rule out a dip tube problem but discounted it because of the 4000 hours. However if there has been an engine change that alters everything.

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

[onanov]

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?

[Col_T]

Not so much a thought, more a question. If one dip pipe has corroded, why wouldn't the other dip pipe be corroded?

 

[onanov]

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

[WotEver]

46 minutes ago, onanov said:

Really just trying to find a solution that does not include fitting a new dip tube, as I suspect this may be somewhat tricky

I seem to recall someone describing doing this a while back. It involved a gland that could be inserted from outside the tank iirc. 

[Tony Brooks]

Or a sturdy plate with the new dip tube fixed into it and a ring of screw holes. Drill a hole in the top of the tank (or the side if the tube has a 90 degree bend in it close to the plate) larger than the tube. Drill & tap holes for screws. Secure plate to top of tank with a fuel resistant gasket, maybe closed cell neoprene?

 

Any swarf that falls into the ank will just st in the bottom until you suck it out a the annual tank cleaning and if you grease the drill even less will fall in.

[onanov]

5 hours ago, Tony Brooks said:

Or a sturdy plate with the new dip tube fixed into it and a ring of screw holes. Drill a hole in the top of the tank (or the side if the tube has a 90 degree bend in it close to the plate) larger than the tube. Drill & tap holes for screws. Secure plate to top of tank with a fuel resistant gasket, maybe closed cell neoprene?

 

Any swarf that falls into the ank will just st in the bottom until you suck it out a the annual tank cleaning and if you grease the drill even less will fall in.

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

[RLWP]

On 04/06/2018 at 16:06, onanov said:

 we have a Fuelguard filter on the system (with a glass bowl) and that tends to run with the bowl 1/2 full.

So your air leak is in the pipework between the tank and the fuelguard

 

Take some spanners and see if you have loose pipe joints

 

Richard

[Tonka]

There is a filter in the lift pump marked by black arrow and the white arrow is a priming lever for getting fuel up to the filters. very handy when you need to bleed the engine

[onanov]

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

[Tony Brooks]

1. Yes, plausable

 

2. The head of fuel. The lower the fuel level with a top or high exit pipe the more "suck" the pump will have to create in the pipe. Also with a  full tank you may get a syphon effect.. If its a low level tank exit then the only answer is the head of fuewl in the tank getting lass so you get less syphon effect.

[Bee]

On ‎05‎/‎06‎/‎2018 at 11:06, Tony Brooks said:

Or a sturdy plate with the new dip tube fixed into it and a ring of screw holes. Drill a hole in the top of the tank (or the side if the tube has a 90 degree bend in it close to the plate) larger than the tube. Drill & tap holes for screws. Secure plate to top of tank with a fuel resistant gasket, maybe closed cell neoprene?

 

Any swarf that falls into the ank will just st in the bottom until you suck it out a the annual tank cleaning and if you grease the drill even less will fall in.

Good idea in any case, then you can shine a torch in and get something in the tank to scrape the sludge out. I made a hole by drilling a ring of little holes then bashing the middle out, its like putting your arm down a crocodiles throat but at least its possible. Lovely winter project if nothing better to do!

[onanov]

2 hours ago, Tony Brooks said:

1. Yes, plausable

 

2. The head of fuel. The lower the fuel level with a top or high exit pipe the more "suck" the pump will have to create in the pipe. Also with a  full tank you may get a syphon effect.. If its a low level tank exit then the only answer is the head of fuewl in the tank getting lass so you get less syphon effect.

 

Thanks,

 

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