Fuel leaking from return pipe connection

[robtheplod]

Hi All

 

I really hope someone can help me here as I've discovered a leak in a fuel pipe connection as it attaches to the tank (see pics). I think its been doing this for a long time but having painted the bay I'm now finding lots of little problems..... better when it was dark!

 

it has been firing a mist of fuel for a while but i wasn't able to locate it before - it lays a thin layer on the weed hatch etc. I've tightened up both the fuel pipe and the convertor connector (ringed) but to no avail - not gone too tight just in case. I've noticed the converter is split so not sure if that was me or not tightening but anyway i need to replace this. I've looked about but not sure what the name of the connector is?  it bolts onto the tank which has an inbuilt screw thread. The convertors uses an 18mm spanner but suspect it could be imperial....

 

can anyone throw any light on the name or part and where i might find it?  I'm assuming i cant remove it as fuel will come out as it continuously leaks and the engines not run for 3 weeks?  i dare not touch it anymore in case it becomes a bigger problem!

 

thanks in anticipation from a worried Rob!!!!

 

[Tracy D'arth]

5 minutes ago, robtheplod said:

Hi All

 

I really hope someone can help me here as I've discovered a leak in a fuel pipe connection as it attaches to the tank (see pics). I think its been doing this for a long time but having painted the bay I'm now finding lots of little problems..... better when it was dark!

 

it has been firing a mist of fuel for a while but i wasn't able to locate it before - it lays a thin layer on the weed hatch etc. I've tightened up both the fuel pipe and the convertor connector (ringed) but to no avail - not gone too tight just in case. I've noticed the converter is split so not sure if that was me or not tightening but anyway i need to replace this. I've looked about but not sure what the name of the connector is?  it bolts onto the tank which has an inbuilt screw thread. The convertors uses an 18mm spanner but suspect it could be imperial....

 

can anyone throw any light on the name or part and where i might find it?  I'm assuming i cant remove it as fuel will come out as it continuously leaks and the engines not run for 3 weeks?  i dare not touch it anymore in case it becomes a bigger problem!

 

thanks in anticipation from a worried Rob!!!!

 

Could this be it?  https://www.gasproducts.co.uk/5-16-inch-compression-x-3-8-inch-bspm-t.html        Not sure of the sizes, looks smaller than 1/2" BSP male, 3/8" is the next size,  & could be 5/16" pipe?  You will have to measure it all.

[robtheplod]

1 minute ago, Tracy D'arth said:

Could this be it?  https://www.gasproducts.co.uk/5-16-inch-compression-x-3-8-inch-bspm-t.html        Not sure of the sizes, looks smaller than 1/2" BSP male, 3/8" is the next size,  & could be 5/16" pipe?  You will have to measure it all.

thanks Tracy, this is what i keep finding, but the screw thread is on the tank itself...

[Tracy D'arth]

19 minutes ago, robtheplod said:

thanks Tracy, this is what i keep finding, but the screw thread is on the tank itself...

Ah.   It looks as though there is a male thread on the tank bush which is welded on, so a female thread screws on.   As its split, I am sure its a female thread on the brass union, a male would not have split.

  This do it?   https://www.bes.co.uk/wade-compression-straight-adaptor-5-16-x-3-8-bsp-pf-9474/

 

Edited June 13, 2022 by Tracy D'arth

[RollingFoggy]

41 minutes ago, robtheplod said:

thanks Tracy, this is what i keep finding, but the screw thread is on the tank itself...

Take it off, measure it up as best you can and post up the sizes. So outside diameter of the copper pipe going in, and either inside diameter of the fitting or ! Outside diameter of the stub on the tank.

[robtheplod]

1 minute ago, RollingFoggy said:

Take it off, measure it up as best you can and post up the sizes. So outside diameter of the copper pipe going in, and either inside diameter of the fitting or ! Outside diameter of the stub on the tank.

danger is that if i remove it it might not seal when it goes back on as fuel continually leaks  or am i being paranoid?! 

[RollingFoggy]

Just now, robtheplod said:

danger is that if i remove it it might not seal when it goes back on as fuel continually leaks  or am i being paranoid?! 

Is it above the fuel level in the tank, can you remove it without all the fuel running out ?

[RollingFoggy]

4 minutes ago, robtheplod said:

danger is that if i remove it it might not seal when it goes back on as fuel continually leaks  or am i being paranoid?! 

At the moment you say you have a fine mist spraying of fuel. A fine spray on a hot surface is ignitable. So that fitting has to be safely removed and not used ever again, right now !

[robtheplod]

looking to sort asap - plus boat not going anywhere for a while.....

 

is the solid fuel pipe generally 5/16" connections?

[RollingFoggy]

2 minutes ago, robtheplod said:

looking to sort asap - plus boat not going anywhere for a while.....

 

is the solid fuel pipe generally 5/16" connections?

Possible but no one knows, take some measurements to be absolutely certain. No point having folk trying to guess a diameter from a photo, or what it should be on paper !

[springy]

Might be worth having a good look around the ring on the nut which retains the copper pipe - if its "wade" brand they are often marked with the size of the compression fitting.

 

springy

[ditchcrawler]

9 minutes ago, RollingFoggy said:

Possible but no one knows, take some measurements to be absolutely certain. No point having folk trying to guess a diameter from a photo, or what it should be on paper !

Could even be metric

 

[Alan de Enfield]

Wrap some 'diesel proof' self amalgamating tape around it  use the boat until the fuel level drops below the level of the pipe, then remove it and repair it properly.

[Tracy D'arth]

1 minute ago, ditchcrawler said:

Could even be metric

 

Oh don't complicate the issue!   5/16"  and 8mm are interchangeable, there is so little difference. I'll bet on 5/16 and 3/8 bsp.

[RollingFoggy]

1 minute ago, ditchcrawler said:

Could even be metric

 

Indeed, it could well be a BSPT - 8mm or a BSPP - 5/16" or someone with access to jet 1 fittings could have welded an NPTF  fuel fitting on there, no thread sealant required.

[robtheplod]

ok i need to do more digging, sorry, will come back tomorrow!  thanks!!

 

i'll give my jerry can contents to the guy in the next boat and syphon out 20 litres hopefully that will be enough!!

[David Mack]

As long as the fuel tank is not full, and you are not running the engine, then you can safely remove the fitting, and the only fuel which may be released is that already in the pipework locally. Undo the smaller nut and you should be able to retract the copper pipe from the fitting which has split. Then you can unscrew the split fitting.

If you have a vernier gauge, measure the diameter of the copper pipe (on a straight section away from the end fitting), and also measure the external diameter of the pipe stub on the tank, measuring the unthreaded part (clear of the weld to the tank).

Post the measurements here and someone can confirm the particular fitting size you need.

[Tracy D'arth]

Scaling the photo off the 18mm spanner size of the brass body, I reckon it could well be only 1/4" BSP Male thread and 5/16" pipe.

[reg]

My first point of call, although I haven't used it for sometime, is the BES catalogue.

https://www.bes.co.uk/pipes-tubes-and-fittings/pipe-fittings/compression/

 

They give pretty comprehensive descriptions and measurements.

[Peugeot 106]

I had the same problem and fitting. There is no valve on the return line so if the fuel level is above the fitting it will leak outcontinuously. Unless you break the siphon it will carry on and siphon all your diesel into the bilge even when the fuel level is below the tank fitting.

 

this is a complete pain if you are changing the fuel filter or have a leak in any return line.

 

i filled my tank to brim for winter and had to run for 50 hours to get it he level low enough to fit a full nite 8mm ball valve. I will only use the valve for filter changes or emergencies, I was  going to fit a non return valve but was advised for my engine it doesn’t like any back pressure hence the full bore ball valve 

 

obviously you could lower the tank diesel level with a pump into a can but remember the syphon effect and either blow down the tube or crack open the connection to stop it. Mine looks like yours and is 5:16” (8mm) fuel pipe standard compression fitting 

 

if if you fit a valve remeber not to run the engine with it closed. I Will hang the ignition key off it as a reminder when it is closed!

 

if you would like photo I can get one in the morning 

I discovered all this in Wigan with a cracked copper fuel return line. Half the bloody tank siphoned into the bilge. Not too bad at 75p/ litre but now...

 

hooe thus helps 

59 minutes ago, Tracy D'arth said:

Oh don't complicate the issue!   5/16"  and 8mm are interchangeable, there is so little difference. I'll bet on 5/16 and 3/8 bsp.

That’s where my money is too. I can’t see why it would be anything else

[Peugeot 106]

I’m assuming your return line dips into the bottom of the tank. It obviously won’t siphon if it doesn’t but a lot do seem to dip into the tank. The jury seems to be out as  to which is best! Mine dips to the bottom hence the siphoning

[robtheplod]

20 minutes ago, Peugeot 106 said:

I had the same problem and fitting. There is no valve on the return line so if the fuel level is above the fitting it will leak outcontinuously. Unless you break the siphon it will carry on and siphon all your diesel into the bilge even when the fuel level is below the tank fitting.

 

this is a complete pain if you are changing the fuel filter or have a leak in any return line.

 

i filled my tank to brim for winter and had to run for 50 hours to get it he level low enough to fit a full nite 8mm ball valve. I will only use the valve for filter changes or emergencies, I was  going to fit a non return valve but was advised for my engine it doesn’t like any back pressure hence the full bore ball valve 

 

obviously you could lower the tank diesel level with a pump into a can but remember the syphon effect and either blow down the tube or crack open the connection to stop it. Mine looks like yours and is 5:16” (8mm) fuel pipe standard compression fitting 

 

if if you fit a valve remeber not to run the engine with it closed. I Will hang the ignition key off it as a reminder when it is closed!

 

if you would like photo I can get one in the morning 

I discovered all this in Wigan with a cracked copper fuel return line. Half the bloody tank siphoned into the bilge. Not too bad at 75p/ litre but now...

 

hooe thus helps 

That’s where my money is too. I can’t see why it would be anything else

thanks for that... fitting the ball valve sounds sensible...  interesting re syphon effect. no idea where mine goes - top or bottom, but assume then that if i undo these it *could* stop the siphon and give me the opportunity to change........

[Peugeot 106]

Once the fuel level is below the fitting you will break the siphon by undoing the return pipe and thus letting air into the top of the inverted loop and the siphon is broken. You can then mess about to your hearts content. If you don’t break it fuel will dribble out forever 

 

i think a valve is worthwhile. It makes changing the fuel filter a lot drier work

 

All best

 

[dmr]

The bit fixed to the tank is most likely BSP. The broken bit will then be a stud coupling with female BSP at one end to (probably) either 5/6 or 8mm. More likely 5/16 but could be 8mm. 5/16 and 8mm are interchangeable as far as copper pipe diameter is concerned (and so olives) but the threads are not compatable, the nut on the copper pipe will have a BSP thread if its 5/16 or a metric thread if its 8mm. In the worse case the threads will bind up before the olive is compressed.

 

Measure that copper pipe, if its about 8mm then get both a 8mm metric and 5/16 imperial coupling, they don't cost much.

 

An approximate measurement of the bit welded to the tank should identify what BSP thread it is.

If it turns out to be NPT then do lots of swearing and go to the pub, but its very unlikely. 

[Steve56]

6 hours ago, ditchcrawler said:

Could even be metric

 

Definitely imperial as indicated with the shoulder at the top. Metric fittings have the shoulder at the bottom. On odd occasions some of the manufacturers nowadays don't seem to bother with this. The pipe in the photo is probably 5/16. Don't mix and match metric and imperial fittings, it's just a bodge and is asking for problems further down the line. I would say the problem you have is that the pipe coming from the tank has a tapered thread and your fitting has a parallel thread. Obviously been forced on and caused the split. As someone else has already mentioned you should really have a ball valve fitted in the return line.