Fuel leaking from return pipe connection

[robtheplod]

1 hour ago, Tracy D'arth said:

How did you remove the old olive from the pipe?

the old one was crushed (holds hand up)... used a pipe cutter to get a fresh piece..

[Tracy D'arth]

20 minutes ago, robtheplod said:

the old one was crushed (holds hand up)... used a pipe cutter to get a fresh piece..

Fine, just wondered if you had marked the pipe where the olive sits.

[Tony Brooks]

The number of threads showing under the nut in the photo suggest to me that the olive may be cocked on the pipe or not as tight as it should be, so taking it off and inspecting is a good idea. The olive should be a few mm away from the end of the pipe, not right on the end.

[Peugeot 106]

5 hours ago, robtheplod said:

Hi All, visited today and was able to sort with all the parts and all the great help you gave.... all connections are fine although my compression joint leaks ever-so slightly.. happy to give it some time to see if this resolves or i need to redo - don't want to over tighten!

 

thanks for everyone who helped me!!!!

 

rob

 

 

I’m not sure what will happen if you run the engine with the return line closed. To be on the safe side, I hang my ignition key off it when I close mine. 

[BEngo]

4 hours ago, reg said:

Typo?

Or something else I don't know?

 

Good info by the way. I'm never sure how tight to make a joint so I probably err on the side of over tightening.

Free add in by the fone!

N

[BEngo]

Looking again at the photo, and Tony's comment about the amount of thread showing on the pipe fitting, you did screw the right end of the fitting into the tap?  With the nug off and the olive out it is easy to fit the thing wrong way round.q

 

The fitting has the same thread either end, except that the pipe end has a chamfer round the hole where the pipe goes, so that the between them the nut, which also has an inside chamfer, and the fitting chamfer squeeze the olive onto the pipe.

 

N

[Tracy D'arth]

4 minutes ago, BEngo said:

Looking again at the photo, and Tony's comment about the amount of thread showing on the pipe fitting, you did screw the right end of the fitting into the tap?  With the nug off and the olive out it is easy to fit the thing wrong way round.q

 

The fitting has the same thread either end, except that the pipe end has a chamfer round the hole where the pipe goes, so that the between them the nut, which also has an inside chamfer, and the fitting chamfer squeeze the olive onto the pipe.

 

N

Well spotted, thought the thread was too long. Reckon you hit it on the head.  Its a little knowledge is dangerous again.

[robtheplod]

Thanks all for your helpful comments, removed the nut, reseated the olive, tightened up and bingo, we have a good joint... no leaks!  will keep and eye on it with a drip tray with paper towel in so i can easily see if its no good. but ran the engine for 30 mins and it all held.....  so pleased i've done this job - think it may have been leaking for a long time......

[robtheplod]

Now this is done, it would be good for me to know the purpose of the return pipe?  I know the engine draws from the main feed and returns via this one but I'm not really sure why?  does it take more than it needs/can use and returns?  thanks!!

[David Mack]

The lift pump takes more fuel than the engine needs and passes it to the injector pump. This meters out the precise quantity required by the engine according to the engine speed, load and speed control setting, with the excess fuel being passed back to the tank. This also has the advantage that any air in the fuel line is returned to the tank, so helps with bleeding the system.

[PaulJ]

19 hours ago, Peugeot 106 said:

I’m not sure what will happen if you run the engine with the return line closed. To be on the safe side, I hang my ignition key off it when I close mine. 

Well I dont know about the OPs engine but I got called out to a Sabb once that would start OK,tickover  and then die as fast as you could get it into gear.

After much head scratching and checking I found a tap in the return line (?!) which the owner had managed to shut without realising. So for at least single cylinder Sabbs, thats what happens..

[dmr]

7 minutes ago, David Mack said:

The lift pump takes more fuel than the engine needs and passes it to the injector pump. This meters out the precise quantity required by the engine according to the engine speed, load and speed control setting, with the excess fuel being passed back to the tank. This also has the advantage that any air in the fuel line is returned to the tank, so helps with bleeding the system.

 

Also most injectors deliberately "leak" a tiny bit of fuel to provide lubrication and cooling to the injectors. This is why the return line should connect the injectors and injection pump back to the tank. Blocking the return can therefore cause all sorts of trouble.

[Peugeot 106]

22 hours ago, Peugeot 106 said:

I’m not sure what will happen if you run the engine with the return line closed. To be on the safe side, I hang my ignition key off it when I close mine. 

 

2 hours ago, dmr said:

 

Also most injectors deliberately "leak" a tiny bit of fuel to provide lubrication and cooling to the injectors. This is why the return line should connect the injectors and injection pump back to the tank. Blocking the return can therefore cause all sorts of trouble.

Maybe my method of hanging the key off the valve isn’t so daft then!

[robtheplod]

3 hours ago, Peugeot 106 said:

 

Maybe my method of hanging the key off the valve isn’t so daft then!

now its in i'll only be touching it when changing the fuel filters...

[Peugeot 106]

1 hour ago, robtheplod said:

now its in i'll only be touching it when changing the fuel filters...

I will also turn it off when I leave the boat for a long time. If anything leaks you can lose a lot of fuel thru syphoning. That is when I will turn off both feed and return and leave the key as a reminder . I’ve turned the engine on a few times with the supply shut!