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iansutton
iansutton

Posted: Wed Nov 11, 2015 2:24pm

Post Subject: Bleeding fuel system

I find bleeding the fuel system on my narrowboat a real chore. The problem i have is when I change the pre-filter and main fuel filter, it takes me forever using the hand lever on the fuel pump to remove the air from the system. I have lately resorted to using an oil extractor pump to suck the fuel through the bleed points on the filter housings. I think the problem is due to the fuel draining from the pipework when removing the filters, and when the new ones are all fitted and I open the fuel cock, any head of fuel drains back into the tank, rather than flowing down to the pre-filter. The stop cock is located on the stern deck under a hinged cover, at the highest point in the fuel line. I need to come up with a better solution. I have 2 ideas. 1. Fit a valve either side of the pre-filter to prevent the fuel in the pipe draining away when removing the filter. 2. Install a replacement fuel line between the fuel cock and pre-filter with a U bend in it, to retain some of the fuel in the pipeline. (See picture I found of another boat on the Internet). What do you think of my ideas, or do you have any better suggestions

Bleeding fuel system
Tony-B
Tony-B

Posted: Wed Nov 11, 2015 3:04pm

Post Subject: Bleeding fuel system

First of all it is absolutely no use trying to use the "add image" facility because the forum software renders it postage stamp size so apart form seeing the engine in the photo is a Beta I can not see any more detail. Please email the image to Tony@tb-training.co.uk so I can have a proper look at it. I also really need to know the make and model of your engines. If this is a fairly "normal" narrowboat (again no details given) I do not see how fuel can drain back into the tank. The fuel tanks are usually higher than the engine. Many Betas are self bleeding as long as the start battery is in good condition and even then when using the priming lever on the lift pump, diaphragm priming pump, or plunger priming pump (whichever is fitted to your engine) they usually are no problem to bleed. This leads me to wonder if there is a leak in the pipework or pre-filter but again without information about the make and model of the pre-filter it is impossible to comment further. In most cases a small air leak would be bled back to the tank on a self bleeding engine so it may not affect the engine when running. A photo of your own boat's engine area may help. There may also be an issue with priming pump delivery volume. There is no reason apart from a greater chance of air leaks why you should not fit a valve either side of the pre-filter but even then the pre-filter would still be full of air that would have to be bled out. It would also be useful if you can describe exactly what the pre-filter element and the fuel in the old filters look like. I need more information as to what you have and what is going on. Please email photos and further information.

Tony-B
Tony-B

Posted: Thu Nov 12, 2015 9:58am

Post Subject: Bleeding fuel system

Ian has emailed me some photos and given me some more information. I have replied with some specific suggestions about his next diagnostic steps. I will report back here when I know the outcome.

Tony-B
Tony-B

Posted: Thu Nov 19, 2015 10:08am

Post Subject: Bleeding fuel system

I have been discussing this by email and working on it for inclusion in the magazine. Here are the results. I suspect its the lift pump. On the basis of the information you have sent me I doubt your diagnosis as long as this is a normal narrowboat with the fuel tank above the uxter plate and against the back of the hull. Despite the fuel pipe entering the top of the tank unless you drain the whole fuel pipe when the filter is off there will still be a head of fuel to siphon the fuel down to the primary filter. The inverted U bend shown in the photo will certainly minimise any tendency for air to enter the pipe when the filter is changed as long as the main fuel tap is turned off. There is no reason that you can not fit taps either side of the primary filter apart from having extra joints that make faults marginally more likely. Are you aware that there is one position in every two engine revs that will render a mechanically fuel lift pump all but inoperative if the engine stops in that position and engines tend to stop in only one or two positions. If yours has taken to stopping in that position then operating the priming lever will not deliver much fuel. You can tell if this is the case because the priming lever will operate with very little resistance against it. First of all try turning the engine over one complete turn and re-trying the lever with a bleed screw open. If that is not the problem then either air is leaking into the system between tank and lift pump or the lift pump is faulty. Turn the fuel tap off and disconnect the fuel pump outlet. Spin the engine on the starter while catching the fuel delivered. You should get at least half an eggcup full every two revolutions. If it is less then either the pump is faulty or there is a blockage between tank & pump. Try blowing back down the pipe into the tank. It will be difficult because of the primary filter and the head of fuel. Next disconnect the inlet pipe (fuel tap off) and put your finger over the inlet. Spin the engine on the starter for a few revolutions. Pause 30 seconds and then take your finger off. The pump should have held vacuum. Do the same for the outlet but this time it should have held pressure. If it fails on either count the lift pump is faulty. It may be cheaper to leave the faulty pump in place and fit an electrical lift pump fed from the ignition switch. Facit is one readily available make. If the fuel pump is OK then you need to look for air leaks into the system. The Beta version of your engine is self bleeding, given sufficient battery charge, so if you combine a small suction from the elements in the injector pump with the fuel head in the tank the engine might bleed sufficient air back into the tank to allow it to run. Your filter looks as if there are no sealing washers on the pipe unions but if the fittings have taper threads in the filter head some form of sealer rather than washers would be used. I can not see any sealing washers under the bleed screws. They may well be small copper washers and if so change them for new ones because the old ones are probably now very hard. Make sure the large rubber ring seal in the filter head is in good condition.

iansutton
iansutton

Posted: Mon May 23, 2016 8:39am

Post Subject: Bleeding fuel system

Hi Tony I know this is a late reply to this post, but it has taken me a while to get around to investigating this problem. I have replaced all of the flexible fuel hoses in the fuel system and renewed all the joints on the copper fuel pipe. Along with cranking over the engine a ¼ turn before bleeding, I now think I have eliminated the problems with bleeding the fuel after a service and air getting into the fuel lines. However as a final thing, I would like to fit an electrical fuel pump instead of the lift pump that is fitted. I see that you recommend fitting a Facet fuel pump, however there are quite a few different models, so could you recommend one suitable for my engine, which is a Nanni Diesel 4.150HE. Kind regards Ian.

Tony-B
Tony-B

Posted: Mon May 23, 2016 9:07am

Post Subject: Bleeding fuel system

First of all turning the engine over 1/4 of a turn only turns the camshaft 1/8 turn so will do virtually nothing. Turn the Engin one complete turn. I do not thing it will matter much which Facit fuel pump you fit (or any other make) because its only a 1.5 litre engine and the fuel tank is probably above the pump level. It will also have short pipe runs. If you fit the cylindrical one it probably has a small filter under a bayonet cap at one end. This is no problem as long as the pump comes after the primary filter and you remember the filter is there and needs changing now and again. I know RCR tend to fit the box shaped pump though. It is probably cheaper.

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