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Diesel Fuel System Question - Filter Blocked


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Thanks for looking. For a start I'm not sure the filter is actually blocked but it sounds like it, so the thread title is designed to show up in future searches.

I have experience of rebuilding petrol engines but little of diesels and even less of diesels in boats. As reported in my restoration thread the engine which usually starts very easily fired, spluttered and stopped last time. Every attempt since then, it just turns over without firing. It hasn't been started for over a year. I did put some diesel in the tank back then with additive, but I didn't fill it.

I have read the instruction manual but I would like to ask those with experience for any tips on a good procedure to shorten my learning curve and save me from filling the bilge with smelly diesel.

Referring to the pic below: I have hilighted two pipes and a "filter". The upper pipe with the yellow trace goes to the fuel filter on the rear of the engine, out of sight.

--When creating this question I realised how few pictures I have of the engine bay. This one is from Boatshed when they were trying to sell the boat in the past.--

Am I correct that the lower pipe is the return? What is the "filter" with the tap?

Thank you in anticipation.

1548406141_s-l1600(11).jpg.4fe3c98bb9aac19aaebb6a5680eef63a.jpg

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The filter with the arrow looks like a regular cav pre-filter possibly with water separator in place of filter, it should go from there to engine lift pump then to engine filter then to injector pump, there should be a priming lever on the lift pump for bleeding, this needs the camshaft in the right position to operate properly or will only give short strokes.

Engine filter should have a bleed screw, open and work the primer lever till fuel comes out and close screw, if you loosen the metal pipes slightly at the injectors and crank engine over with throttle full open(out of gear) till fuel starts coming out and nip the pipes up while cranking it will often fire up, any misfires need a bit more bleeding.

Return pipe is usually from pipe linking the injectors, some have one from injector pump as well.

Of course not easy to see exact plumbing from your piccie.

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on water rail there is a bleed screw and priming pump on the top of the filter housing- make sure the washer on the bleed screw isnt cracked or it will let air in. also slacken the injectors one at a time as you are cranking until you get a good squirt of diesel out, then tighten, once you have got rid of all the air, it should start.

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If you've had that cav filter apart at all it's very easy to fit a new o ring with the old one still in place as they sit quite deep in the groove, result is usually an air leak into the system and if the filter is above fuel level you won't see any diesel leaking to the outside to give it away.

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same happened to me.

Check any fibre washers or replace any in doubt. its been some time dry. As told to me, you cant keep reusing some washers and it may be good practice to replace those that get disturbed. I did and it made a difference.

Have a method to boost your battery. we had to cross connect with leisure battery to keep the amps up. The faster it spins the better.

Its the last bit from pump to injectors that's the trick. At least on my engine you bleed two injectors and they fire, pump pressure clears the rest and I've seen that in action.

Again, as others have said, be methodical, work in a logical way.

It took more pumps on my lift pump than I would have thought.

 

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Thanks for all the helpful replies so far.

Sounds like there will be spillage so I'll take some old rags and something to put them in when finished. It looks like Brian Wards have filters etc so I won't have far to go to replace stuff. I'll try jumping the battery first and if it starts, fine for now. If I have to disturb anything though, it would make sense to go through the system and replace all the O rings, filters etc that get disturbed just so I know they're done. It's on the to do list before we go cruising anyway, same with the sump and gearbox oils.

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I had a simiar problem back in May. It was wateer in the ful tank. The Boulters engineer prooved this by loosening the fuel line at the injector aand turned the engine over. What came out was an emulsionof fuel and water.

He used a Pela type vacuum pump attachd to a length of copper pipe to drain water from the bottom of the tank. he changed both filters then bled the system aas previously described.

I have seen an engineer (from Whispering reeds) bleed the system using the Pela pump, which saved a lot of time.

The symptoms of this problem were exactly as you describe. Good luck.

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My pela tactics are made even simpler by using a non return bleed nipple meant for brake calipers on each engine filter in place of the normal screw, just nip the top section open with a rubber pipe to pela, suck till bubble free fuel appears in the clear tube of the pela, pull off the rubber pipe and the suction clears the pipe and close the nipple at leisure with no air going back in and job done with no diesel to clear up.

Cost £25 per engine to do but paid off in convenience especially when my tanks were rotten and changing filters several times per sea trip, now got new stainless tanks.

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There's a lot of Pela about isn't there? I had to google him.

20210915_091008.thumb.jpg.e9037dfb4acf02e1a663ab259cc7eed2.jpg

I bought one of these from Aldi/Lidl (can't remember) in anticipation of changing the oil. I reckon a long, rigid extension pipe would be a good idea to clean out the bottom of the diesel tank via the filler?

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As long as it's a straight filler that would do fine if it can handle the head it has to lift to prime, I did much the same on my old boat but now have a 90 degree bend going into my tanks, I made sure my new tanks had drain valve tappings though.

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Hi Floyd First WHAT have you touched/done, if not, is tank tap in open position?, is there fuel above outlet pipe? if all correct undo the small plug/ on top of the filter housing 1/2 to one turn then work pump handle up and down(if it feels loose not much resistance turn engine over half a turn} then continue, if no fuel ejects from bleed screw you have a air leak, easiest way to find after checking by finger is to remove pipe from tank attach a length of hose with funnel on end of pipe pour fuel into hose while holding it above engine then check all joints, filters rarely block and not standing still .John

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  • 4 weeks later...

Thanks again everyone, here's an update. Ultimate Speed oil pumps are in Lidl again for £9.99 if you're quick. I'm sure I paid £12!

Reading the replies again I see Smoggy was spot on. I was at the boat on Saturday and I am very lucky to have some great neighbours in Brundall Gardens. One of them showed me the set up on his boat which is a similar, and made things a little clearer.

I haven't tried to do anything yet but having had a good look around I now understand what I need to do. I did take some decent pictures though:

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Pre filter water separator - do I drain it? I have removed the lid of the water strainer housing and drawn around it so as to make a better fitting gasket!

20211009_123728.thumb.jpg.118f7e4adc1c3d82872ad7e54b18b238.jpg

Found the lift pump, I wondered why there was a 6 inch nail sticking up for a start! :facepalm:

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Filter will be a pig to get to; my hand was holding the phone under the floor to take this shot.

Thanks to you guys and my mate in Brundall I will have a bit more confidence when I have a go at it. I'm pretty sure the engine battery is dead but I'll leave replacing it until next season. In the meantime I'll be making an extension tube for the Pela pump in case the tank needs hoovering out.

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Plumbing looks to be tank to valve to water strainer to lift pump to engine filter to injector pump.

Injector pump leak back to engine filter spare inlet, injector leak back to engine filter bleed screw and back to tank, so that operating the lift pump without engine running should bleed engine filter back to the tank it's just a case of knowing when it's full, any leaks on engine filter should show up by diesel leaking as it's on the pressure side so unfound air leaks getting in are likely to be at the water seperator, if you drain that one you will need to bleed although small amounts of air should naturally self bleed the way your tank return is plumbed.

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