Jump to content

Diesel Fuel System Question - Filter Blocked


Recommended Posts

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

Link to comment
Share on other sites

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.

  • Thanks 1
Link to comment
Share on other sites

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.

  • Thanks 1
Link to comment
Share on other sites

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.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

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.

 

  • Thanks 1
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

  • Thanks 1
Link to comment
Share on other sites

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.

  • Thanks 1
Link to comment
Share on other sites

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

  • Thanks 1
Link to comment
Share on other sites

  • 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:

20211009_123702.thumb.jpg.2a701b9be374f20cbef21ba0c4a4ba82.jpg

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:

20211009_123804.thumb.jpg.6650451de5d980bb81c77be61b28605e.jpg

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.

Link to comment
Share on other sites

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.

  • Thanks 1
Link to comment
Share on other sites

  • 8 months later...

And.....

20220706_123159.thumb.jpg.8f141a175e606b376d11bf20e81416c0.jpg

I now have it all fitted but then left it because I didn't have the right size spanners and I couldn't get good access for the adjustable. Not wanting to round anything off or undo something I wouldn't then be able to tighten (yep, got the tee shirt:default_dunce:) I decided to leave it and refer back to this thread for the bleeding procedure. 

Link to comment
Share on other sites

On 11/10/2021 at 21:48, Smoggy said:

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.

I now understand this a bit better. I think; have I got this right? :

Turn the engine over by hand until I get maximum stroke of the lift pump. Loosen the large screw on top of the filter housing at the injector leak back pipe union. Pump away until I get a good flow of diesel. Would I be right to expect a good flow to start with, then air until it clears?

Link to comment
Share on other sites

You won't get any diesel until you have filled the filter bowl - and the water trap filter if you have cleaned that also - so you may be pumping for some time.  It is quicker to loosen the banjo union on the feed pipe to the injector pump. On the top of the filter cover, this should have a moulded arrow pointing outwards.  Once you have diesel flowing, tighten this fitting and finish bleeding from the top fitting.

I think you will find your injector pump has two bleed nuts, which can be seen in your photo as small black fittings on the side of it towards the back.  Do the lower one first, which is the pump body and then the upper one, which is the casing of the mechanical governor.  You may have to do this more than once.  If the engine still will not start, loosen the feed pipe nuts at the injectors, turn the engine on the starter and check that you are pumping diesel up to them. If not, start the bleeding all over again from the filter, until you are.

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

That sludge in the top of the filter looks like your tank could do with a clean or at least a good dose of bug treatment although I've found bug sludge to be blacker than that.

Marine 16 claims to break the sludge down as well as killing the bug so may be work a good dose, that's what I use but I think all the treatments work in different ways.

  • Thanks 1
Link to comment
Share on other sites

it looks similar to the sludge I found in the bottom of water rails filter, I was told this may have been caused by cold weather waxing up the fuel in the filter (why you change the filter at the beginning of the year when taking the boat out of winterised mode, rather than at the beginning of the winter)

  • Like 2
  • Thanks 1
Link to comment
Share on other sites

32 minutes ago, Smoggy said:

That sludge in the top of the filter looks like your tank could do with a clean or at least a good dose of bug treatment although I've found bug sludge to be blacker than that.

To me, it looks typical of the rust that will come off a mild steel fuel tank.  It would be interesting to have seen what sort of state the sediment trap filter was in!

  • Like 2
Link to comment
Share on other sites

On 07/07/2022 at 05:46, Vaughan said:

You won't get any diesel until you have filled the filter bowl - and the water trap filter if you have cleaned that also - so you may be pumping for some time.  

Without that golden nugget of info, I would probably have given up short of completing the job. Thank you Vaughan. 

20220707_102557.thumb.jpg.5d8b96273e782c5ae8fb04c6e79ed352.jpg

The nut you refer to is one of those guarded by a steel plate. I was going to leave the job until the next visit but decided to make nasty smells in the bilge this trip which could then clear a bit before I get back again. So I loosened the top nut and soon got the "feel" of the pump; the full movement of the lever wasn't a full stroke of the pump, just the last part. Luckily the top of the engine is quite flat so I was able to lay along it and save my back muscles. It did seem to take for ever. I had an 8mm socket which fit the pump bleed screws ok and they didn't take so long.

The plan was then to jump the dead engine battery from the leisure batteries and try a start. But then I had a very productive couple of days aboard so it could wait till next time...   Really? No. 

I have two sets of keys for the boat and only one set has the engine key. Both sets look the same at a quick glance; with cork ball, but the "spare" set is usually at the back of the cupboard. Someone had a reshuffle and you can guess the rest. Yes I could have tried with a bit more effort but to be honest I wanted to finish the visit away from work, with a bit of fishing.

Next time then....

  • Like 1
Link to comment
Share on other sites

Well done so far!

I gather your engine has been standing for some time, so don't be frightened to spill a lot of diesel when you are bleeding, to make sure all the little air bubbles are passed through.  With the older type rotary injector pumps, the smallest amount of air will stop it working.

If you have to bleed up to the injectors (you probably will) make sure you set the Morse control lever to max acceleration (in neutral) before turning the engine over on the starter.  That way, the injector pump is pumping plenty of fuel up the pipes.  No fear of the engine starting and galloping away, as you have loosened the feed pipe nuts, so the injectors themselves will not function until you tighten them again.

I usually cut the bottom off an old plastic anti-freeze container, or the bottom off a mineral water bottle and hold these under the filter housing and the injector pump, while bleeding.  Also good for changing oil filters.

  • Thanks 1
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Sponsors

    Norfolk Broads Network is run by volunteers - You can help us run it by making a donation

×
×
  • Create New...

Important Information

For details of our Guidelines, please take a look at the Terms of Use here.