So Air Bubbles in the Fuel Line Are No Big Thing

[rebel heart]

I cleaned out the fuel tank, including removing the inspection port by which the primary intake pipe is plumbed. This (and cutting off the hose that attached to it) introduced what I thought would be a decent amount of air.

I filled the tank back up, and thought "well, I'll run the diesel till it dies from the air bubbles, then bleed out the bubbles and restart".

I started the engine, waited an hour, went sailing, motored back in later that night, never having even a slight hiccup. I have Racors and I watched the bubbles fly through the filters.

Diesel smart guys, what gives? Nigel Calder makes it seem like a single molecule of air will kill your engine.

Yanmar, 4JH.

[S/V Illusion]

The 4JH is among the Yanmars which essentially self-bleed. Some others are not that user-friendly

[Stillraining]

Originally Posted by S/V Illusion

The 4JH is among the Yanmars which essentially self-bleed. Some others are not that user-friendly

What he said

Don't know about that particular engine....but I definitely have ones that are more cantankerous then others.

Depending on the rest of your plumbing and filtration set up the bubbles you see " Flying through your racor" arnt necessarily making it to the injector pump or injectors themselves...if they were you would definitely have hick ups....maybe not enough to stall your engine but make it stumble or loose power anyway.

[Chief Engineer]

You must have said a prayer to Saint Bleedius of Purgistan...the patron Saint of Diesel Engines.

Seriously, Racors can accept a small amount of air.....I have removed the tops of them and found the fuel level to be well below the filter element

[Sailmonkey]

Any engine that is "self bleeding" , in otherwords one that returns many times more fuel to the tank than it could ever hope to use will hardly notice air bubbles.

[delmarrey]

Originally Posted by S/V Illusion

The 4JH is among the Yanmars which essentially self-bleed. Some others are not that user-friendly

Yep! The 3JH too! Here is a page out of the 4JH manual.


.

[daddle]

Originally Posted by delmarrey

Yep! The 3JH too! Here is a page out of the 4JH manual.

Using a wrench By that term I suppose it's self-rebuilding too? I would think self-bleed means you do nothing but operate the pump. That's the way my Beta (Kubota) is. Or the earlier Universal (Kubota). I've never loosened any bleed screws. Not ever. Not on the filter or anywhere. Somebody solved the problem.

[delmarrey]

Originally Posted by daddle

Using a wrench By that term I suppose it's self-rebuilding too? I would think self-bleed means you do nothing but operate the pump. That's the way my Beta (Kubota) is. Or the earlier Universal (Kubota). I've never loosened any bleed screws. Not ever. Not on the filter or anywhere. Somebody solved the problem.

It self bleeds out the small stuff while running, not a whole fuel line or filter. Read line #6 in the picture of my last post.

[rebel heart]

Originally Posted by Sailmonkey

Any engine that is "self bleeding" , in otherwords one that returns many times more fuel to the tank than it could ever hope to use will hardly notice air bubbles.

Interesting. I've heard that the return line from the 4JH spits a ton of fuel back into the tank; I guess that's part of it.

[rusky]

Originally Posted by rebel heart

Interesting. I've heard that the return line from the 4JH spits a ton of fuel back into the tank; I guess that's part of it.

I have the 4jh2-ute and yep, on our particular engine, the return is significant.

[noelex 77]

Originally Posted by delmarrey

Yep! The 3JH too! Here is a page out of the 4JH manual.


.

Note there are several bleeding techniques for the 4JH series of engines depending on build date.
BTW I am interested in which engine and year was that from Demarrey

[delmarrey]

Originally Posted by noelex 77

Note there are several bleeding techniques for the 4JH series of engines depending on build date.
BTW I am interested in which engine and year was that from Demarrey

I have a 2009 3JH4E.

[noelex 77]

Originally Posted by delmarrey

I have a 2009 3JH4E.

Thanks for that.
Interesting its only a year later than mine with a very different bleeding system. The 4JH5 is different again.