Bleedin' Diesels

[chriscallender]

Bleedin\' Diesels

At the weekend I changed the fuel filters on my Bukh 20. I changed both the primary (CAV type) and the fine fuel filter on the engine. Its all running now so no big problem, but I had a bit of a struggle with the bleeding.

The problem is that the primary filter is well above the level of the fuel, so I can't get gravity to do the work when getting the air out the CAV filter and filling the bowl. The outlet pipe emerges from the top of the diesel tank, and then goes uphill to the primary fuel filter. In the end, I disconnected the hose from the tank, poured diesel into it via a filter funnel, and got the CAV filter filled that way. I suspect I could have made things slightly easier by making sure that the diesel tank was full to the brim. However, even then the fuel has to leave the tank by a connector on the top and then further uphill to the filter, so it can't be filled by gravity.

I'd like to make filter changing much easier to do in the future, so that if I ever get contaminated fuel I can change the filter without any struggle, even at sea if necessary. One idea I had was to fit some kind of pump between the tank and the primary fuel filter. How about those bulb type things that are used to prime petrol on outboards? I found this article


http://www.sailnet.com/collections/articles/index.cfm?articleid=woodto044
which suggests that they can be used on diesel engines. Failing that I could presumably find a 12v electric diesel pump but that seems like overkill and will be used so infrequently that it might not work when I need it.

So onto my real question. Has anyone ever fitted one of those outboard primer pumps to a diesel engine. Will it pump diesel OK? Will it help me bleed the bleeder? Are there any safety considerations that make this a bad idea?


Chris

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[oldharry]

Re: Bleedin\' Diesels

Lifting fuel from the tank against gravity is a good way of ensuring that fuel line leaks or fractures do not flood the boat with diesel - with the attendant fire risks. I do not know your particular engine, but there will be a fuel lift pump - usually worked from the engine camshaft, and this will have a lever which allows you to operate it manually for the specific purpose of priming the pump and fuel lines.

Another way round bleeding a system like yours is to seal the fuel tank breather, and pressurise it just enough to lift the fuel to the 'top' of the system, allowing you to bleed it that way. I once used a rubber bung with a bicycyle pump on an awkward installation! Just make sure there is plenty of fuel to avoid air reaching the lines!

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[chriscallender]

Re: Bleedin\' Diesels

Hi

I did use the lift pump, but unfortunately its not speedy when the whole filter is full of air so I speeded things up using a filler funnel and filling the filter up that way. Ideally I'd like to fit something that makes the job dead easy so that I'm not tempted to skimp on maintenance and also in case I need to change a filter in difficult conditions.

Pressurising the tank sounds like a good idea, and one I hadn't thought of. Perhaps thats the way to go, maybe all I need to do is make up a bung and carry a bicycle pump.

I can see how its a good idea to lift fuel from the tank in case a pipe fractures.

Thanks

Chris

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[tcm]

Re: Bleedin\' Diesels

I have a straightforward manual pump fitted on the diesel line for exactly this purpose, though it is for higher-volume than a bulb pump thing so it's seems more like a bilge pump. Works fine -if it pumps petrol (or presumabkly a bilge pump too must be petrol-resistant in case the bilges are full of fuel) it will have no problem doing the same for diesel. You need to have suitable (just simple on/off) valves to put the pump online and the rest of the circuit off-line when pumping. The rest of that article looks good advice too.

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[JerryHawkins]

Re: Bleedin\' Diesels

Did mine recently. Worked out a really neat way to do it...

I disconnected the rubber fuel pipe where it connects to the engine, then used an oil extraction pump (Pela spherical type in my case) to suck the fuel and air through the system. Did this until clean fuel with no air bubbles was coming through. Re-connected pipe to engine leaving only a tiny amount of air to be bled off from the engine filter bleed screw using the lift pump manual lever to force it through. May not have needed to do this final bleed as the amount of air was to small.

BTW - I hate the CAV type filters. No way could I change this at sea. I've installed a Separ KWA20 in parallel (can switch between old CAV and new KWA20 whilst engine running). CAV will be my "backup filter" and KWA20 the main one. The filter in this is changed from the top and can be done without the need to bleed the system afterwards!! See http://www.separ.co.uk if intrtested.

Cheers,

Jerry


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[snowleopard]

Re: Bleedin\' Diesels

hit a similar problem to yours. in my case the tank is above the engine but as the fuel is drawn from the top of the tank i have to start a syphon to get fuel into the primary filter. after a lot of fooling around i fitted a bulb to start the process. it works fine.

i was a bit worried that the ones for outboards might not take kindly to diesel so i got mine from a peugeot dealer, specifically designed for a diesel car (the 306D). they are also available from citroen and probably a few others.

incidentally i looked at how they do it on hte land rover which has a big marine-type water separator: they run the piping so the separator is downstream of the lift pump.

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[chriscallender]

Re: Bleedin\' Diesels

Thanks everyone for all the ideas I would never have thought of - using the oil changing pump to create a vacuum, pressurising the tank, or maybe getting a diesel bulb for a car. Certainly sounds like it doesn't need to be as difficult as I made it yesterday! Although I got all the air out eventually and that is the main thing...

Chris

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[snowleopard]

the vital question-

could you use your chosen method of bleeding when the system gets air in it at night as you are approaching the harbour mouth in heavy weather?

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[hlb]

Re: Bleedin\' Diesels

I have this problem when fuel is low. Fill the filters with fuel before fitting them. Then do it the easy way. Undo a couple of injector pipes. Stick a rag over them and start engine. Then tighten them whilst still running. You might spray a bit of diesel about, but its fast and effective.

<hr width=100% size=1> <font color=blue> Haydn

 

[bedouin]

Re: Bleedin\' Diesels

Going off on a slight tangent - I am glad to say that my fuel feeds from the bottom of the tank, and will "gravity feed" right the way to lift pump. That way if there is a leak it will be "out" not "in". So fuel will drip into the bilges, where it can be seen, rather than air leaking into the fuel system, which might stop the engine and potentially cause serious damage.

That also makes bleeding at sea a comparatively easy task.

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[johna]

Re: Bleedin\' Diesels

I have often thought of fitting a small elevated tank between the lift pump and the engine mounted fuel filter, a sort of day tank. Engine a Yanmar 2QM20. Anyone have this type of arranngement or any comments adverse or otherwise.

Johna

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[Neal]

Re: Bleedin\' Diesels

You've got lots of suggestions by now, but here's one more.

You could change the CAV filter for a Racor. These have a powerful pump built in which is really neat and works well.

Good luck.

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[LadyInBed]

Re: Bleedin\' Diesels

I went for the lo-tec method - removed the bleed screw and filled using a small funnel.

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[yoda]

Re: Bleedin\' Diesels

My Citroen diesel car has a bulb type primer to achiev just what you want. CAV also make a filter and primer unit all in one which you will find fitted to a rover 218 sd. City Auto Diesel in Plymouth seem to have a number of examples on their display board. Nearly every Diesel car must have a similar problem.

Yoda

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[Jools_of_Top_Cat]

Re: Bleedin\' Diesels

I would be worried about fitting bulbs, as the regs stipulate fireproof fuel pipes. I could be wrong, but I imagine the bulbs you mention would not conform to regs.

I am a hater of regulation, but in order to pass my survey I had to renew all my fuel pipes to conform. You may get a sting if you have to have her surveyed.

Saying that it does appear to be a good idea, deisel tastes foul.

<hr width=100% size=1><font color=blue> Julian </font color=blue>

<A target="_blank" HREF=http://www.ukstaffords.com>http://www.ukstaffords.com</A>

 

[jimboaw]

Re: Bleedin\' Diesels

Install a simple shut off close to the input side of the filter. That should prevent most of the fuel running back to the tank when you remove the filter. As suggested by others fill the filter before re-fitting

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[roger]

Re: Bleedin\' Diesels

Beacause my fuel tank is in the keel, Betamarine provided me with a 12v pump along with my new engine. It makes filter bleeding very easy indeed. It runs all the time and makes somewhat of a racket - now thankfully blanketed by the sound insulation. They are obviously available but I've no idea of the price.

<hr width=100% size=1>Roger

 

[chriscallender]

Re: Bleedin\' Diesels

A few people have suggested filling the filter before refitting. However I don't understand how this is possible - there are rubber seals eg between the bottom of the filter and the top of the water bowl that will only be compressed and sealed once the central bolt through the whole assembly is done up.
Try to fill it up before its reassembled and it seems to me all you will get is diesel all over your hands. Unlike the fine (engine) filter which is a doddle in comparision (I'd expected it to be harder before I started).

So I believe a CAV type filter can't be filled until after it has been put back together, unless I am missing something.

Chris


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[saturn]

Re: Bleedin\' Diesels(duplex)

if you want to fit something thats really easy then you could fit duplex filter,this is two filters in one that after first priming both you can change from 1 to 2 and change one while the engine is still running through the other,bet motor boaters use them.

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[Oldhand]

Re: Bleedin\' Diesels

I have success by filling the filter bowl with clean diesel before installing it then some furious hand pumping of the manual lever on the engine's fuel lift pump. However, the simplest way to get a hand pump in the feed system is to change your CAV type filter for a Racor brand filter unit with a built in hand pump. This was standard fit on my last boat and worked well. Your local engine dealer should be able to recommend and obtain a sutiable Racor unit.

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