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Old 01-05-2015, 17:42   #16
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Re: How does self bleeding work?

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Originally Posted by Wotname View Post
Jdi, your explantion is quite correct however let me add one more comment.

The HP pump (injector pump) can only deliver a very small VOLUME of fuel into the injector line thus if this line mostly full of air which is compressible, the pressure created by adding a small amount of fuel into the line into the line remains low.

Only when the line is full of fuel, can the HP pump deliver the required pressure by adding a small amount of fuel into the already full line of uncompressible fuel.
Yes, that is what I was TRYING to say but obviously didn't do a good job at it. Thanks for clarifying !
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Old 01-05-2015, 17:45   #17
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Re: How does self bleeding work?

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Yes, that is what I was TRYING to say but obviously didn't do a good job at it. Thanks for clarifying !

You did great, I didn't read it properly - my bad. Please see my edit to my previous post
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Old 01-05-2015, 17:54   #18
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Re: How does self bleeding work?

My Mitsubishi engine is self bleeding as proclaimed in its manual. It somehow detects air and activates an auto bleed system that is separate from the rest of the regular fuel system. No idea how it works and have only had it come on after filter changes as I try very hard not to run out of fuel and have so far succeeded.

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Old 01-05-2015, 18:29   #19
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Re: How does self bleeding work?

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My Mitsubishi engine is self bleeding as proclaimed in its manual. It somehow detects air and activates an auto bleed system that is separate from the rest of the regular fuel system. No idea how it works and have only had it come on after filter changes as I try very hard not to run out of fuel and have so far succeeded.

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WAG...
Detects low pressure and allows the injector pump to seriously increase it's pumped volume until pressure is high enough to crack the injector so the air is driven into the cylinder. When pressure is approaching normal operating range, pump reverts back to controlled volumes.
Again, merely WAG...

BTW, how long does this self bleeding take and is there any indication while it is occurin???
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Old 01-05-2015, 19:07   #20
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Re: How does self bleeding work?

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Originally Posted by Wotname View Post
WAG...
Detects low pressure and allows the injector pump to seriously increase it's pumped volume until pressure is high enough to crack the injector so the air is driven into the cylinder. When pressure is approaching normal operating range, pump reverts back to controlled volumes.
Again, merely WAG...

BTW, how long does this self bleeding take and is there any indication while it is occurin???
Not long and it makes a "chug chug chug" noise. It does it with the ignition on and the engine not running.

Should note only if bleeding is required, otherwise it doesn't trigger.

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Old 01-05-2015, 20:26   #21
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Re: How does self bleeding work?

Here is a quote from page 9 of my Westerbeke manual. Notice it differs between self priming and bleeding...

"For INITIAL STARTS:
The self-priming feature of the W-46 is different from other models in that it requires longer time. Two circuits are
required to bleed both fuel filter and injecion pump. Therefore, when priming the W-46 for the first time or when the system has been worked on or has been run out of fuel, allow the electrlc fuel pump to operte for 2 to 3 minutes before the first cranking effort. simply turn the ignition
key ON to activte the electric fuel pump."

So, in theory its supposed to self-bleed but I have not found this to be the case when running out of fuel (only once!). It then goes on to say:

"The engine can be started by taking steps described on pages 9 and 10. In cases where the engine cannot be started easily, loosen two injection nuts on the nozzle side, turn the speed control lever to "full open" position, turn the starter motor and then tighten the nuts firmly."
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Old 01-05-2015, 21:54   #22
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Re: How does self bleeding work?

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Sharp knife across the wrist is effective I believe..

No, No, No... it is "down the road, not across the street"
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Old 02-05-2015, 09:36   #23
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Re: How does self bleeding work?

My 2001 Yanmar is self priming/bleeding (Yanmar calls it bleeding). As you can see from all the chatter there aren't many who know what it is. Me neither, I just say thank you for the easy starting engine.
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Old 02-05-2015, 10:19   #24
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Re: How does self bleeding work?

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Sharp knife across the wrist is effective I believe..
I was considering the throat.
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Old 02-05-2015, 10:36   #25
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Re: How does self bleeding work?

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1 As you can see from all the chatter there aren't many who know what it is.

2 Me neither, I just say thank you for the easy starting engine.
2 But, of course. Couldn't agree more.

1 Here are the basics, admittedly I do NOT know the engineering details. On our M25, I have to open the bleed valve (the "knurled knob" that all Universal owners know of). It allows fuel to flow around the injector pump and back to the return line to the tank. In a recent discussion on bleeding our M25 series and M35 engines on our C34 forum, there was mention of leaving this knob slightly open, which would make the M25 a self-bleeding engine. With that knob cracked, it bleeds the engine. Once the engine starts I close the valve and the engine has worked fine for my 17 years of ownership. Other skippers with the same engine have left theirs cracked a bit with the same success in operation. The M35s have no knob, and are self-bleeding, essentially having an open "knob" although one is not physically present.

Priming is a completely separate issue, and is only based on having an electric fuel lift pump in addition to the mechanical pump on the engine. The lift pump gets the fuel to the engine. It's called a "lift" pump because many boats have fuel tanks below the level of the engine. On our boats the tank is higher than the engine. The pump then is there to simply overcome the friction in the fuel lines to get the fuel to the engine. Many of our skippers report that the engine will still work if the fuel pump dies for any reason, generally until the tank is less than half full, since the height of the fuel in the fuller tank can overcome the hoses' fiction loss.

I can "prime" my engine without even filling up a new empty fuel filter. I just turn on the electric fuel pump!

Yes, it's semantics, 'cuz part of the bleeding process is getting fuel to the engine.

But I simply think of it as a two step process: 1) fuel "prime" could be done with that horrible pump on the Racor housing, but my fingers thank me for never having to use it! ; 2) actually "bleeding" which on my engine is the knurled knob over the injector pump.

I could do 2) without 1) but with more difficulty, since the engine can't pull fuel through an empty filter.
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Old 02-05-2015, 11:26   #26
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Re: How does self bleeding work?

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I HAVE a westerbeke 46. They may call it self bleeding but it really is just self priming. Ask me how I know. During a normal change of the fuel filters it will self bleed just fine but if you run out of fuel you will need to bleed the injectors... and that takes quite a while.

A mechanical fuel pump will do the same thing but you need to pump that little sucker on top of the fuel filter about 3 billion times to get the fuel through the system.
I have a Volvo 2003 with mech. fuel lift pump with the lever you speak so (lovingly?) of.
My finger got tired too,so I instd. a 5/16" outboard squeeze bulb in fuel line,between tank & primary filter. Finger much happier & no slit wrists.
Len
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Old 02-05-2015, 11:46   #27
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Re: How does self bleeding work?

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I have a Volvo 2003 with mech. fuel lift pump with the lever you speak so (lovingly?) of.
My finger got tired too,so I instd. a 5/16" outboard squeeze bulb in fuel line,between tank & primary filter. Finger much happier & no slit wrists.
Len
Len, those priming bulbs are not made for diesel. Maine Sail did a writeup on them a while back showing one that cracked. His point was that by the time you're done, it may be more cost effective to get an electric fuel pump. Your boat, your choice.
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Old 02-05-2015, 12:09   #28
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Re: How does self bleeding work?

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Len, those priming bulbs are not made for diesel. Maine Sail did a writeup on them a while back showing one that cracked. His point was that by the time you're done, it may be more cost effective to get an electric fuel pump. Your boat, your choice.
Thanks -I wasn't aware of problems.Saw the idea somewhere on i-net couple yrs ago. Will chk it before launch. / Len
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Old 02-05-2015, 12:34   #29
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Re: How does self bleeding work?

I Have a Westerbeke 82B4. Yes it can self bleed. The electric fuel pump provides enough suction / pressure to draw from your Racor and force the fuel to the injector pump where it then follows the return back to the tank. This is done by turning your key on. If you have your engine cover off you should hear the pump if you are near the engine. Keep the key on for about 30 -45 seconds before you start and have the throttle open a little. It really works, even if the Racor wasn't filled completely when you changed filters!
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Old 02-05-2015, 13:17   #30
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Re: How does self bleeding work?

pressing the preheat button should not start the electric fuel pump, it should come on when the key is on. preheat button should only heat the glow plugs, most engine require pressing both the glow plug and the start button to start the engine.
well that is how most of the boats I have worked operate.
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