No fuel from tank

[Georgina]

One for those with degree in Physics. Two of us went to Georgina last weekend to make new fuel lines to both engine and diesel stove. The stove one went without hitch and works fine. Feed from the main tank to both stove and engine is via two ball type fuel cut off valves which are new, and both have been working perfectly. The replacement of the engine line involed removing and scrapping the old copper tube and replacing it with a single new length to a newly purchased manual fuel suction pump (to facilitate bleeding), then a new water trap type filter and a new flexible line connected direct to the base of the engine lift pump. All made and connected and look beautiful. However actuating the new manual pump sent fuel the wrong way and was heard to pump air into the main tank. Much cursing. Pump appears to have been incorrectly assembled in factory - but this another story of no interest here. Solution, so as to get things working again, was to take new assembly apart, remove pump, and reassemble with the line going directly to the new water trap filter. This was done but no success with trying to bleed engine. Disconnect pipe at filter - still no fuel. Disconnect pipe at cut off valve and turn on valve - no fuel come out. Long, fine screwdriver through hole - no fuel. Even longer cable tie poked in and wriggled about, no fuel but cable tie comes out wet!

 

So we have a tank full of diesel, checked and dipped, tank full, fuel level about 18 inches above fuel cock. Other fuel cock to stove working and passing fuel. Fuel cock for engine immediately beside other cock, turned on but no fuel. Air bleed to tank checked and OK. Why no fuel?

 

Matter resolved by reconnecting copper pipe then poking other end of line into seperate hand syphon pump, making crude seal with rag, and working syphon. Result - fuel gushed merrily. Reconnect system, bleed and start engine which works perfectly during test run of several hours. Question:- why no fuel out of tank when tank full and fuel cock turned on. Answers on a postcard, please.

[STUBAG]

One for those with degree in Physics. Two of us went to Georgina last weekend to make new fuel lines to both engine and diesel stove. The stove one went without hitch and works fine. Feed from the main tank to both stove and engine is via two ball type fuel cut off valves which are new, and both have been working perfectly. The replacement of the engine line involed removing and scrapping the old copper tube and replacing it with a single new length to a newly purchased manual fuel suction pump (to facilitate bleeding), then a new water trap type filter and a new flexible line connected direct to the base of the engine lift pump. All made and connected and look beautiful. However actuating the new manual pump sent fuel the wrong way and was heard to pump air into the main tank. Much cursing. Pump appears to have been incorrectly assembled in factory - but this another story of no interest here. Solution, so as to get things working again, was to take new assembly apart, remove pump, and reassemble with the line going directly to the new water trap filter. This was done but no success with trying to bleed engine. Disconnect pipe at filter - still no fuel. Disconnect pipe at cut off valve and turn on valve - no fuel come out. Long, fine screwdriver through hole - no fuel. Even longer cable tie poked in and wriggled about, no fuel but cable tie comes out wet!

 

So we have a tank full of diesel, checked and dipped, tank full, fuel level about 18 inches above fuel cock. Other fuel cock to stove working and passing fuel. Fuel cock for engine immediately beside other cock, turned on but no fuel. Air bleed to tank checked and OK. Why no fuel?

 

Matter resolved by reconnecting copper pipe then poking other end of line into seperate hand syphon pump, making crude seal with rag, and working syphon. Result - fuel gushed merrily. Reconnect system, bleed and start engine which works perfectly during test run of several hours. Question:- why no fuel out of tank when tank full and fuel cock turned on. Answers on a postcard, please.

 

The answer is, simply, SIPHON.The tank will be fitted a "dip tube",and during your ministrations you will have broken the siphon-loop, restoring it when you sucked the fuel over the top of the loop.Well done!

[Georgina]

I didn't know that. I assume that this is a U shaped tube going upwards. What is its purpose? I have sailed for nearly 50 years and used numerous sea going boats and they do not have one. New to canals though. New to son-in-law as well - and he is a qualified and experienced engineer. Is this idea one of those which only apply to inland waters - there seem to be a lot of these.

 

Many thanks for the information

 

Malcolm

[by'eck]

Most diesel fuel tanks take fuel from the top of the tank via an internal tube which stops just short of the bottom. Nothing different on a canal boat.

 

Stubag was referring to the fact that you have to lift fuel with a suction initially after which flow will be maintained via siphon effect assuming no air leaks.

 

Operating the lift pump with bleed screw open on secondary filter (fitted immediately after the pump) is the usual way of pulling the air out of the system after which it should flow on demand from the tank.

[Georgina]

Thanks again. However my diesel tank takes its fuel direct from a tap at the bottom of the tank, about an inch up. I have had this set up before on other boat tanks. I am not happy with it because of the possibility of taking in sludge and water from the tank bottom - but that is what I have got. Having said that I have never had a problem with this type of set up, even on sea going boats where tanks are shaken about. We relied on water trap primary filters - which is why we were doing this job. I suppose it is possible that my present tank has an internal pipe going up and down but I think it unlikely as it would be an unnessesarily difficult way to build a tank. So I am back to my first question. Why did the fuel not come out? Judging by the silence seems to have baffled everyone. Do other people have this type of tank set up?

[Keeping Up]

For a while it was a BSS requirement that fuel pipes must exit from the top of the tank, and then travel back down outside the tank. It caused a number of previously-safe boats to have to be modified, with a new take-off pipe being fitted to emerge right under the steerer's feet where it inevitably got damaged. The theory was that if there was a leak in the pipework, the fuel wouldn't all flow out into the bilge; the person who wrote the rules was presumably unaware of the principles of syphoning which would ensure that once the pipes were full of fuel, then any leak in the later pipework would just syphon all the fuel out, so there was no real improvement in safety.

 

Of course, there had to be an internal pickup pipe for the fuel, so the fuel effectively passed through an inverted U of pipes; this could cause a problem in getting the fuel to flow again after running out. Our own boat was being built at the time, and rather than have the pipes leave the tank from the top the boat builder sought - and was granted - permission for the inverted U pipe to be entirely inside the tank rather than outside it. The pipe then emerges through a tap fitting near the bottom of the tank.

 

It sounds as if perhaps you have a similar arrangement.

[mrsmelly]

Thanks again. However my diesel tank takes its fuel direct from a tap at the bottom of the tank, about an inch up. I have had this set up before on other boat tanks. I am not happy with it because of the possibility of taking in sludge and water from the tank bottom - but that is what I have got. Having said that I have never had a problem with this type of set up, even on sea going boats where tanks are shaken about. We relied on water trap primary filters - which is why we were doing this job. I suppose it is possible that my present tank has an internal pipe going up and down but I think it unlikely as it would be an unnessesarily difficult way to build a tank. So I am back to my first question. Why did the fuel not come out? Judging by the silence seems to have baffled everyone. Do other people have this type of tank set up?

 

Hi

 

Most older boats did as does yours take the fuel straight from the bottom of the tank. My first boat did that and could sometimes allow crud to get to the filter. The Bss, mot is a new piece of legislation relating to canal boats and has not been in force very long, less than twenty years in fact so prior to that many different types of fuel system were used. Is yours an oldish boat ?

Just googled it and in fact it is a very very new piece of legislation only 15 years old so if your boat is prior to 97 it could have anything the builder wanted.

Tim

Edited September 24, 2012 by mrsmelly

[Georgina]

Hi

 

Most older boats did as does yours take the fuel straight from the bottom of the tank. My first boat did that and could sometimes allow crud to get to the filter. The Bss, mot is a new piece of legislation relating to canal boats and has not been in force very long, less than twenty years in fact so prior to that many different types of fuel system were used. Is yours an oldish boat ?

Just googled it and in fact it is a very very new piece of legislation only 15 years old so if your boat is prior to 97 it could have anything the builder wanted.

Tim

 

Hi, Tim,

 

Yes my boat was built 1996, so that is why this type of tank set up was used. Easy for builder but possible problem for future owners. Apart from the new water trap and filter I intend to use my long syphon device to take a sample from the bottom of the tank and see what it is like. If bad I will syphon some muck off the bottom and ditch it. Still no ideas forthcoming as to why the fuel would not come out. Spoke to diesel engineer today, admittedly cars, and he has never heard of this happening.

 

Malcolm

[Keeping Up]

Hi

 

Most older boats did as does yours take the fuel straight from the bottom of the tank. My first boat did that and could sometimes allow crud to get to the filter. The Bss, mot is a new piece of legislation relating to canal boats and has not been in force very long, less than twenty years in fact so prior to that many different types of fuel system were used. Is yours an oldish boat ?

Just googled it and in fact it is a very very new piece of legislation only 15 years old so if your boat is prior to 97 it could have anything the builder wanted.

Tim

 

The BSS may be only 15 years old but its predecessor (Boat Safety Certificate) was around when our boat was built in 1991. It must have been the BSC rather than the BSS which first required pipes to emerge from the top of the tank.

[mrsmelly]

The BSS may be only 15 years old but its predecessor (Boat Safety Certificate) was around when our boat was built in 1991. It must have been the BSC rather than the BSS which first required pipes to emerge from the top of the tank.

 

Not sure but what I am sure is that there was no compulsery anything about for inland boats when I first lived aboard a narrowboat and I am a relative newbie in the scheme of things as i only moved aboard in 89 so call it what you like it is a very new concept

 

Tim