Diesel and air leaks! Blasted beggaring ball breaking barsteward!

Cardo

Cardo

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So...

I posted a little while back about having air entering our fuel system somewhere around the CAV filter. We eventually diagnosed it was the Eberspacher fuel take that came from the second fuel outlet on the CAV filter. As a temporary measure, I removed the Eber fuel pipe and taped up the outlet. After managing to bleed the filter, things worked fine.

Fast forward a month or so and we have now properly blocked off the second outlet and had a lift pump inserted prior to the CAV filter in order to assist with bleeding the fuel system (as the engine's fuel pump just wasn't cutting the mustard).

But now we have developed a nasty air leak into the CAV filter. I have narrowed this down to a leak up to the filter inlet as the bubbles appear out of the bottom of the filter element, so the air is entering on the inlet side of the filter body. Having played around with the new lift pump, I find that if I pump with the bleed screws closed diesel will drip (not gush) from the joint where the copper fuel pipe enters the CAV filter. I'm guessing/hoping this is also the source of the air leaks when the engine is running.

I have removed the pipe from the filter body to see how this seals. I enclose a photo of the pipe... (Apologies for slight out of focus, camera was playing silly beggers)
pipe.jpg

The copper pipe ends in a "nib" that wedges into the inlet on the filter body. The "nut" screws into the thread on the filter body and pushes the nib into the inlet. I presume this is meant to create a seal. However, the nib and copper pipe itself don't seem to be one, there is play between them. Is this normal? Or have things gone awry? Or should the compression of the nib as the nut pushes it in create the seal? In which case, any thoughts on how to improve the seal? I have checked the condition of the copper pipe and it seems to be ok, I can't see any obvious cracks.

Thoughts??
 
You could try reassembling it with a diesel-resistant sealant (Hermetite or similar). But perhaps replacing that short piece of tube might be a better idea.
 
pvb said:
You could try reassembling it with a diesel-resistant sealant (Hermetite or similar). But perhaps replacing that short piece of tube might be a better idea.
Click to expand...

This latter suggestion was on my mind. The fuel system currently has a gate valve at the outlet of the fuel tank (low down) and a further gate valve by the inlet to the filter (high up). This particular piece of pipe runs between the second (upper) gate valve and the filter. The new lift pump is in between the two valves.
Is this second valve necessary? I was wondering whether it would make sense to simply bypass the second valve and run a pipe from the new pump directly to the filter?
However, the valve by the tank is not as easy to reach and I wouldn't really want to try it if the engine were hot, so I guess this second valve is useful in circumstances where the diesel feed needs to be cut off in a hurry, whilst the engine is running.

Who came up with these things?!
 
Looks like a normal compression joint. The nib as you call it is just an olive slid on the pipe. Is there a sealing washer up inside the nut? Failing getting a new pipe then a new nut and olive and, as suggested, some sealant. A local place that sells hydraulics stuff would be a good source of all these things.
 
Looks like a compression fitting and the "nib" you are referring to is an olive. The olive is compressed onto the pipe by tapers on the threaded "nut" and the corresponding fitting on the filter. In water plumbing olives are sacrificial and should ideally be replaced each time the joint is remade, i would have thought that fuel pipes are similar. Does the olive slide off the end of the pipe? If so take it in to your local supplier and get a couple of new ones, however as pvb says it may be best the replace the entire length of pipe as the copper is also scored once the olive is compressed onto it and therefore you may not get a good seal even with a new olive.

Hope this helps a bit.
 
emsworthy said:
Looks like a compression fitting and the "nib" you are referring to is an olive. The olive is compressed onto the pipe by tapers on the threaded "nut" and the corresponding fitting on the filter. In water plumbing olives are sacrificial and should ideally be replaced each time the joint is remade, i would have thought that fuel pipes are similar. Does the olive slide off the end of the pipe? If so take it in to your local supplier and get a couple of new ones, however as pvb says it may be best the replace the entire length of pipe as the copper is also scored once the olive is compressed onto it and therefore you may not get a good seal even with a new olive.

Hope this helps a bit.
Click to expand...

Good info, it might be possible that mixed metric/imperial sizes have been used.
 
I have discussed this with the boss (SWMBO) and decision has been made to replace the copper pipe and upper gate valve (which has the same type of compression fittings, which are seized big time) with a new valve and rubber pipe to the filter.

Therefore, new system would be
lift pump - rubber pipe - valve - rubber pipe - filter

Does that sound sensible?

Also, if new valve, are gate valves recommended for fuel systems, or should we get a ball valve?
 
Cardo said:
Does that sound sensible?

Also, if new valve, are gate valves recommended for fuel systems, or should we get a ball valve?
Click to expand...

Rubber pipe will be fine. A ball valve would be preferable; only a quarter turn needed, so easier in an emergency.
 
You'll need a suitable hose tail and proper fuel pipe clips where you connect to the CAV and valve. Apparently ordinarily jubillee clips aren't suitable. Your original fuel pump May be ok but the diagram/nrvs May be shot. Cheap enough to replace like for like. Afterall it was adequate before this problem occurred.
 
ghostlymoron said:
You'll need a suitable hose tail and proper fuel pipe clips where you connect to the CAV and valve. Apparently ordinarily jubillee clips aren't suitable. Your original fuel pump May be ok but the diagram/nrvs May be shot. Cheap enough to replace like for like. Afterall it was adequate before this problem occurred.
Click to expand...

What are these proper fuel pipe clips? All I've ever seen used is bog standard jubilee clips.

The lift pump (with built-in NRVs) had better be ok, it's brand spanking new!

The fun will be finding the appropriate hosetail for the filter body. Joy!
 
ghostlymoron said:
You'll need a suitable hose tail and proper fuel pipe clips where you connect to the CAV and valve. Apparently ordinarily jubillee clips aren't suitable. Your original fuel pump May be ok but the diagram/nrvs May be shot. Cheap enough to replace like for like. Afterall it was adequate before this problem occurred.
Click to expand...

What are 'proper fuel pipe clips' please? Thanks Jerry
 
If there is a lot of play between the olive and the pipe it could just be that the compression fitting hasn't actually been compressed. Normally would expect the olive to be fairly tight on the pipe, slide if pushed hard but no play.

Clean the joint carefully, including where it goes into the filter, and under the olive if it slides. Screw up the nut by hand then a little bit more with a spanner. Not too much to distort but enough to cause the olive to deform to grip the pipe and seal.
 
Judging from the OP's picture and description of a loose olive this is something I have seen before on a few occasions where take offs from filters have been used in heating applications and is a simple cheap fix. The olive has failed to be compressed correctly because the thread is too short on the compression fitting or the wrong size olive has been used, I have seen both, correct size olives and longer threaded fittings are available, usually from my box which sorts it out. As you will have to go and buy some fittings anyway the other suggestions for rectification are equally valid if more expensive.
 
dovekie said:
This sort of thing I think (http://www.asap-supplies.com/marine/316-stainless-steel-jubilee-superclamps), which I gather are less likely to not squeeze the section of hose right under the screwthread. Hopefully others wiser than me will add their wisdom.
Click to expand...

Great clips but not available in the sizes needed for fuel systems, what is needed are Jubilee "mini" clips like these http://www.ebay.co.uk/itm/MINI-FUEL...-PETROL-PIPE-ALL-SIZES-IN-STOCK-/300709654222 , a bit difficult to find in stainless but perfect for the job, as are crimp on fuel line clips but they have the disadvantage of being non reusable.
 
If you are going to be using olives then I would suggest getting the softer copper variety rather than brass. Will make a difference on soft copper pipe.
 
In the past I have found that if you have a partial blockage somewhere that the lift pump is sucking like mad and creating vacuum in the pipes, which causes otherwise sound joints to let air into the system.

How confident are you that the fuel can flow freely from the tank?
 
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