Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 15-08-2015, 20:25   #1
Registered User
 
stillbuilding's Avatar

Join Date: Jan 2008
Location: Hong Kong
Boat: Custom Freya 20m
Posts: 961
Self bleeding diesels?

I have had issues on a Cummins 4BT diesel engine with air leaking into the fuel supply. I have Racor 1000 filters above engine level with a Holley Fuel pump pushing into the engine which has the usual lift pump.

An extremely well qualified diesel mechanic advised not to worry about bleeding air out because the Cummins was "self bleeding" and while it might run a bit rough while doing so that it would continue running and eliminate any minor air in the lines.

Now i have to say that this has not been my experience with this motor and that stoppage has been an issue such that i have installed a three way valve just before the motor inlet to more easily drain any air.

I have gone through the air leakage stuff and have now eliminated the leak but this notion of "self bleeding diesels" still rumbles about in the back of my mind.

Any validity to this idea?


Sent from my iPhone using Cruisers Sailing Forum
__________________

__________________
stillbuilding is offline   Reply With Quote
Old 15-08-2015, 21:43   #2
Registered User
 
transmitterdan's Avatar

Join Date: Oct 2011
Boat: Valiant 42
Posts: 4,030
Re: Self bleeding diesels?

Self bleeding doesn't mean it will run with a lot of air in the fuel intake. There can be so much air that there is not enough fuel and then no engine will run.

I think what they mean by self bleeding is that if you get all (or nearly all) the air out up to the lift pump then you can expect a self bleeding engine to take care of the rest. That's good because then you don't have to go around and bleed every injector as you do on some engines.

My Yanmar 4JH3E is "self bleeding" and I have never had to bleed it. When I change Racor filters I just fill the bowl up to the top and put the cover on. It starts right up and runs every time.
__________________

__________________
transmitterdan is offline   Reply With Quote
Old 15-08-2015, 22:03   #3
Registered User

Join Date: Aug 2010
Location: sydney, australia
Boat: 38 roberts ketch
Posts: 1,021
Images: 3
Re: Self bleeding diesels?

diesel engines are fantastically reliable - they have one achilles heel - they must have a clean, sealed fuel supply. There is no way to filter air out of the supply side of the system, and no engine will run with air leaking into the supply side. Some engines can have a bleeding effect on the return system, but its useless if air is leaking in to the supply side. self-bleeding most often means - where the fuel supply has been detached for whatever reason, drained , then re-attached - ie sealed - if the return system has good bleeding characteristics, running the starter long enough can remove air from the supply side simply because eventually there is nothing else to pump in but fuel. Being able to bleed your diesel is about as basic as being able to change the sparkplugs on your car, should be about the first thing you learn to do.
__________________
charliehows is offline   Reply With Quote
Old 16-08-2015, 00:52   #4
Registered User
 
Snowpetrel's Avatar

Join Date: Jul 2012
Location: Hobart
Boat: Alloy Peterson 40
Posts: 3,071
Re: Self bleeding diesels?

A Cummins 4BT I sailed with wouldn't self bleed. I had to crack an injector to get it running. At least it started with only the one injector cracked, unlike some diesels which seem to need every injector cracked and bled to get them to fire...

Sent from my HTC_0PCV2 using Cruisers Sailing Forum mobile app
__________________
My Ramblings
Snowpetrel is offline   Reply With Quote
Old 16-08-2015, 02:08   #5
Registered User

Join Date: Jun 2010
Posts: 393
Re: Self bleeding diesels?

Yanmar 3YM30 self bleeds
__________________
olaf hart is offline   Reply With Quote
Old 16-08-2015, 03:56   #6
Registered User
 
Reefmagnet's Avatar

Join Date: May 2008
Location: puɐןsuǝǝnb 'ʎɐʞɔɐɯ
Boat: Nantucket Island 33
Posts: 2,737
Re: Self bleeding diesels?

My Mitsubishi diesel self bleeds. Even with the Racor fuel bowl empty. It makes a clicking sound when the ignition is switched on until the air is expelled. No idea how it works.

Sent from my SGP521 using Cruisers Sailing Forum mobile app
__________________
Reefmagnet is offline   Reply With Quote
Old 16-08-2015, 07:12   #7
Senior Cruiser
 
Sailmonkey's Avatar

Cruisers Forum Supporter

Join Date: Sep 2009
Location: Houston
Boat: '76 Allied Seawind II, 32'
Posts: 5,787
Re: Self bleeding diesels?

Quote:
Originally Posted by Reefmagnet View Post
My Mitsubishi diesel self bleeds. Even with the Racor fuel bowl empty. It makes a clicking sound when the ignition is switched on until the air is expelled. No idea how it works.

Sent from my SGP521 using Cruisers Sailing Forum mobile app

That's an electric fuel pump. No magic there.
Your engine should move somewhere around 5-7 GPh while running regardless of consumption. So in essence your polishing your fuel by running the engine


Sent from my iPhone using Cruisers Sailing Forum
__________________
Sailmonkey is offline   Reply With Quote
Old 16-08-2015, 12:09   #8
Registered User

Join Date: Oct 2011
Posts: 2,438
Re: Self bleeding diesels?

Volkswagon/Pathfinder diesels are self bleeding. I never needed to crack an injector. Mercedes automotive diesels can be run out, and just refill, and pump the little hand pump that is on the injector pump (different than a lift pump) and they will usually start without cracking injectors. On the Perkins that I have owned, if you got one tiny bubble in the system, it required going through the whole bleed sequence. These were all older diesels, but I suspect that many newer diesels are self bleeding. Possibly the industrial based engines wont be, because they are more likely to be operated by professionals. Self bleeding could be designed into any diesel system, but there must be some trade-off, or it would be standard in all of them. Does anyone know of a disadvantage to self bleeding??? _____Grant.
__________________
gjordan is offline   Reply With Quote
Old 16-08-2015, 12:37   #9
֍֎֍֎֍֎֍֎֍֎

Cruisers Forum Supporter

Join Date: Apr 2006
Posts: 13,056
Re: Self bleeding diesels?

I expect the disadvantages would be the usual ones: It must either cost money for extra parts, or extra production costs, or, simply requires a better engineer, who in turn will cost more to hire.


Of course a cynic might point out that if an engine requires bleeding, it will create more service business for authorized mechanics....Surely, that would motivate some companies to keep making engines that require crush washers and bleeding rituals?(G)
__________________
hellosailor is offline   Reply With Quote
Old 16-08-2015, 12:41   #10
Senior Cruiser
 
Cheechako's Avatar

Cruisers Forum Supporter

Join Date: Aug 2006
Location: Skagit City, WA
Posts: 19,371
Re: Self bleeding diesels?

It seems I was told my 3GM30 Yanmars were "self Bleeding". I do know it was hard to NOT start them... no matter what I had done in changing filters etc. Cracking one injector usually got them running if they didnt start otherwise.
__________________
"I spent most of my money on Booze, Broads and Boats. The rest I wasted" - Elmore Leonard











Cheechako is offline   Reply With Quote
Old 16-08-2015, 12:55   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: May 2013
Location: Oregon to Alaska
Boat: Wheeler Shipyard 83' ex USCG
Posts: 1,708
Re: Self bleeding diesels?

Detroits don't have air problems unless you have a hole in the fuel line. The is no injection pump. Fuel flows continuously thru the lines and the injectors, controlled by the cam, have a plunger that makes injection pressure.
Most bleeding issues in injector pump engines can be made simpler with an electric fuel pump.
If you're careful about filling replacement primary filters when changing, most of the bleeding issues go away.
__________________

__________________
Lepke is offline   Reply With Quote
Reply

Tags
diesel

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
How does self bleeding work? chris95040 Engines and Propulsion Systems 32 04-05-2015 21:46
Bleeding Fresh Water System rjarrell Plumbing Systems and Fixtures 5 09-08-2008 05:24
Bleeding 4-108 jimisbell Engines and Propulsion Systems 21 24-05-2007 16:36
Bleeding keel seafox Construction, Maintenance & Refit 16 09-05-2007 22:06
Bleeding the fue lines on a Yanmar 3YM30 chesapeakesailor Engines and Propulsion Systems 10 18-09-2006 06:55



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:06.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.