Air in the diesel system

cliffsorge

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1st trip out in new boat today. Ran like a dream but I made the mistake of filling up with diesel!! It was a very slow fill and was bubbling out of the filler often. After about 3 minutes running the engine stopped so I guessed it was air. I bled the system and all was OK for 20 mins or so then the same happened again I re-bled system and the same happened again just as I was reversing into my berth. Oops how embarrassing! I guess I may have to re-route my filler pipe, not an easy job though.

Is this common after a re-fill and what can I do to avoid it happening?


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paulineb

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Is it a brand new boat or new to you? If new to you, it may be that you need to change your filters

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Margem

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Are you sure its Air, i've filled up hundreds of times (with bubbles) but not had this problem, as the take off pipe is at the tank bottom whilst the bubbles are at the top.
Is the tank vent pipe clear?
It could be the dreaded dirty Diesel clogging the filters.

Good Luck



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hlb

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Well its nowt to do with filling it up. It was'nt completely empty was it. Is it new or new to you? Change the filters anyway and re bleed. Sure you know how to bleed it?

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cliffsorge

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Boat is new to me, she is a 1996 Bayliner 2855 with 270 Merc. I'm assured it had a full service back in July and only used for 10 hours since. It appears you all reckon its a co-incidence bit of a biggie but perhaps. The tank was just over 1/2 full so not sucking up any rubbish . I'll try changing the filters and see. Yes I do how how to bleed the system but thanks for asking!
Thanks for the info guys and gals.

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Anchorite

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You have an airleak in the diesel line: if it were gunk in the fuel, bleeding would
be unlikely to move it, anyway you can see the bubbles (air) coming out when you
bleed. Check the fuel line: it's nearly always the connections on the final filter/
lift pump.

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Freebee

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my guess is you have an airleak nothing to do with filling, check all connections are tight and look for perished or damaged fuel lines.

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duncan

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it is only going to start sucking in air in normal use if something has been moved, reconnected, perished(?) etc - from a fuel line perspective - or you have a restriction in the fuel line /system that leads it to suck in air through the weakest joint.
Have you stirred up the fuel tank in a way that the previous owners hadn't for some time?
If you can get at it check the fuel pick up pipe for a blockage

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DavidJ

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Let's first squash the myth about when a tank is near empty that you somehow suck up the dregs. The fuel intake will be a stack pipe which goes to the bottom of the tank full or empty.
On a petrol Volvo a few years back I had a fuel line which didn't leak but sucked in air and starved the carb. Do any of the flexi pipes look damp.
When you vent (bleed) the system do you get bubbles of air.
Check that the filters are firmly screwed down.
I've run out of ideas
David

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qsiv

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so would having the taps under the tanks turned off - particularly if the seal wasnt perfect - or if there was a small service tank. Believe me - I'm talking from bitter experience after an angine rebuild when the engineers forgot to turn on one tank, and I neglected to check their work.

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cliffsorge

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Well £70.00 on for 2 new filters and a tow from the RNLI later, problem still not fully sorted! I was told to check the stop solenoid on the injector pump. After stripping down the top of the engine I proved fuel flow to the pump but it was not leaving the pump. Played around with the connections and by luck it eventually fired up. The trouble is I have proved nothing and I am not confident about the cause. The engine appears to run OK for 30/40 mins and then stops suddenly, as I said last time I could not restart and was towed in. Help........please

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Bejasus

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Check the fuel tank vent as a blockage would cause a vacuum and stop the fuel supply until you open something and relieve the vacuum. Try running with the filler cap off.


Sorry 'oldsaltoz' just read your post suggesting the same thing.


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cliffsorge

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Well its finally sorted. Not air in the diesel at all or indeed anything to do with the diesel, it was a loose connection on the alternator causing an arc which apparently, after a while, was shutting down the management system on the engine. I had asked an engineer to sort it but thought I would give it one last try and just trace all the wiring for the stop solenoid with the help of the main diagram, the first main wire led me to the alternator and the output wire was loose and had obviously been arcing, I tightened this up and away we went, tested for 2 hours, no problem. I suppose it had to be something silly!!


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