Lister LR2 Fuel Leak - over pressure ?

[QDos]

Hi - I hope I can explain what i think is going on :

 

I have a fuel leak from the outlet banjo fitting of the fuel pump - very difficult to get to but I have been able to replace the copper washers with Dowty washers (and change them back agan when it still leaked) - tighening is difficult due to restricted access , but I think that I have managed okay.

When standing, engine off- no leak . Start up (used to leak when running but with new washers does not now) 5-10 mins no leak but after this time a spray of diesel is emmited from the joint that is obviously under a lot of pressure - engine is running fine. Many different combinations of washers and torqueing up the banjo bolt - same result , a fine mist of diesel in the engine compartment and a sustantial drip from the fitting - turning to smoke as the engine heats up.

 

My theory: - is this joint just the weakest part of a system that is over pressure ? The fuel pipe from the pump outlet is brazed copper and goes to the inlet banjo fitting of the fuel filter 6" away - this banjo is large and has another smaller pipe and banjo on the inlet as well - I am not sure what this smaller pipe (looks around 1/4"OD capillary) that goes up over the cylinger head , has two small branches to each cylinger and dissapears off , maybe back to the fuel tank ? - not sure . My guess is that this is a pressure relief system that is not working due to the fact that the small bolt on the banjo fitting is not a banjo bolt , just a normal one - I cant see the purpose of having a normal bolt there on a banjo fitting.

Is the lack of pressure relief causing over pressure at the fuel pump outlet and hence a leak?

How much pressue is the fuel system under ?

Can I replace with new fittings with barbed and braded hose ?

 

Thanks

Quentin

[RLWP]

The small pipe is the spill rail from the injectors and it will go back to the tank. This will also prevent overpressure!

 

Is the face of the banjo fitting scored?

 

Richard

[QDos]

Thanks Richard - that makes sense. So one end of small pipe goes to tank , other end goes to inlet of filter (with two branches for injectors) - if the filter end is blank i.e no banjo bolt - main fuel line has no pressure relief therefore weakest joint may leak due to over pressure.

 

The face of the banjo is not perfect but I can do somthing about that , dont know about the face on the fuel pump outlet as its way down in the well and inaccesable. thought that using dowty washers may help here.

 

Will get a banjo bolt for the filter inlet and see where I go from there.

 

Cheers

Q

[Radiomariner]

Did you anneal the copper washers before putting them back?

 

Edited to add: You may be unfamiliar with this. Heat washers over a gas flame until they glow brightly.and allow them to cool before refitting

Edited June 15, 2014 by Radiomariner

[QDos]

Thanks RM

 

Will try this - am a Mech Eng so okay with the concept of stress relief ....

 

Q