Weeping fuel lines

[TimLamb]

I searched the many forum articles relating to fuel problems but this specific issue doesn't seem to get mentioned.

My MD11c seems to run okay even though some connections in the fuel lines and the filters have always been damp with diesel or weep slightly.

I have just been through the problem (after filter changes etc) of running for 10 minutes, cutting out, bleeding again, running for 10 minutes, cutting out..., which seems to have cured itself, but I appreciate this is probably a poorly seated filter.

My question is, what should I use in the pipe connections to obtain a good seal and stop the weeping - I get the impression the white tape stuff isn't recommended?

I have a mixture of copper and rubber pipes but was also wondering what's best, most economical and legally allowed if any rules apply.

As always, thanks for any advice and responses.

Regards

TL

 

[PetiteFleur]

You must cure all the weeping/leaking unions or you will always have problems as you mention. I was always taught that you should never need any extra sealing compound/tape to cure leaks but others may have other views. To comply with current regs you should have copper piping throughout except for a short flexible rubber length for the final portion to the engine to allow for movement. This rubber length must be of the approved type(can't remember the ISO number) with crimped on copper ends. These are available from chandleries and marine engineers or the internet.
PS - I also had a filter that was difficult to seat without leaking and discovered it had two sealing rings in the groove!! I removed one of them and had no further problems with leaks.

 

[petersto]

I also have a md11c with damp fuel lines. I am sure its not the engine but rather the age of the fuel lines and possible overtightening, hardening and general abuse of the olives and connections. I think a renewal of all connections would be the answer. The funny thing is I have no problems with diesel aromas and the engine runs well. So far I have followed the maxim 'if it aint broke dont fix it.'

 

[TimLamb]

I don't think I explained things clearly, there has always been a problem with weeping/damp connections, but the engine ran okay regardless. The recent problem with cutting out after 10 minutes only started after I had disturbed the whole system when I changed the filters - but seems to have cured itself anyway (although I'm going to check everything in case the problem comes back suddenly at an awkward moment).
Cheers.
TL

 

[rob2]

At one time the rubber fuel pipes on my Sole mini-14 diesel went soft under the pipe clips, allowing air to be sucked in. The symptoms were similar to your description. Initially an inch was cut from the ends and alter erplacements were fitted. No more problems.

Good hoses don't weep!

 

[Talbot]

I had an intermittent problem on fuel lines that was a real pain. I eventually replaced the filter for a racor, replaced all the lines with new copper, and new rubber at the end. I assisted the seal using loctite lockseal (available from motor factors).

Problem solved.

 

[brianhumber]

Sounds like old flex gone porous. flex does have a reccommended life rather like gas piping. You could take the opportunity to change to metal piping apart from flexible length as the nanny state wants but I have seen as many leaks on commercial installations from solid piping as flexible.

Filters should NOT be damp with fuel ever, check the seals and seal faces.
I do not advise 'sealing' tape for connections, some types degrade in contact with the solvents in fuel. However lots of todays 'engineers' can not do without it.

Brian

 

[Bilgediver]

The recent problem with cutting out after 10 minutes only started after I had disturbed the whole system when I changed the filters
+++++++++++++++++++++++++++++++++++++++

This is just a sign of air in the system. These Volvo engines recirculate the spill fuel back to the suction side of the fuel pump so if you didn t get ALL of the air out of both filters before starting then you will have this problem.

The wet filter syndrome is not unusual and one cause is that the CAV and Volvo filters although looking the same actually use elements of slightly wrong length. As the centre bolt on the Volvo filter is machined and threaded to correct length this means that this bolt can become thread bound before it securely clamps the smaller CAV filter. A white metal washer under the bolt head might help.

These filters are also prone to distortion of the upper flange caused by overtightening. You might need to replace the filter if it is the second problem.

If you have weeping compression fittings this is a sign of overtightening and one answer is to cut off the exisiting pipe ends and fit new nipples or even fit new copper.