Universal M25 fuel bleeding?

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Stu Jackson

Quote from: Catalina007 on May 15, 2023, 11:41:50 AM
My setup has only a fuel supply line going into part 33, the bleeder knob. As shown in the diagram
If that knob is open (CCW) and the fuel pump is running, nothing comes out of it.
I would expect to get either air, bubbly fuel, or fuel, or some combination of those.

I don't have a return line coming out of the bleeder assemply as shown in the photo 2  which is not my boat
and what which I believe is what you are describing

That's the correct part manual, the Fuel Camshaft Group.  Part 34 is the fuel inlet joint and part 1 is the injector pump.

Your expectation of air, bubbly fuel or fuel or some combination is just incorrect, that's all.  It appears from further inspection of the diagram (and thanks for that) that the infamous Knurled Knob, part 33, bleed valve assembly, introduces incoming fuel to the injector pump.  I was wrong about the fuel return part of what I said, and in fact have been wrong about this for decades!   :shock: :shock: :shock:

Functionally then I can't answer specifically how it works.  All I know is that nothing should ever come out anywhere near that assembly when you open the nut/Knurled Knob.  Somehow it introduces the fuel and air into the injector pump but if you follow the Bleeding 101 steps using the knurled knob and the electric fuel pump you will get all the air out of the system.

Perhaps someone who is more into the guts of the details of this assembly would chime and and explain it to and for us.

That's one of the beauties of this engine: you don't have to slop any fuel all over your engine to bleed it, it is the simplest and cleanest engine to bleed (other than 100% self-bleeding ones of course!).  I've written this before: when I first got our boat 25 years ago, I was afraid to change the fuel filter because I knew I'd have to bleed the engine and had read so many horror stories on the internet in its infancy.  Once I learned how simple it was, we made sure to document it, hence the Bleeding 101 topic.  Sometimes I hear folks say you have to open injectors to bleed engines and when they share that they have M25 engines, I just wanna pull my hair out, but I send them a link to Bleeding 101!   :clap
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

Ron Hill

Guys & )007 : The fuel return line come out of the "banjo" on the aft (#3) injector on the M25/25XP engines

Years ago I mentioned to Joe Joyce (Westerbeke Service Manager) that I ran my M25XP engine with the bleed valve 1/4 turn open he commented that I had a "Self Bleeding" engine.

Somehow? the Westerbeke engines without a bleed valve like the M35BC and M25B engines  -- are self bleeding!!  :shock:

A few thoughts
Ron, Apache #788

Catalina007

Yes on my engine the return line to the tank comes out of the aft injector.
I bled to the top nut on the injector pump.
I also bled the first injector, but I think teh top of the IP did it.   . 

Stu Jackson

Quote from: Catalina007 on May 15, 2023, 04:27:37 PM
Yes on my engine the return line to the tank comes out of the aft injector.
I bled to the top nut on the injector pump.
I also bled the first injector, but I think teh top of the IP did it.   .

I think what we've been trying to explain to you all along was all that work you did wasn't needed.  All you needed to do was turn the knurled knob open run the pump for awhile until the pitch changed, closed the knob and done.
Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

"There is no problem so great that it can't be solved."

Catalina007

Opened knob and ran pump for a long time.
Pitch never changed.
Engine wouldnt start
Bled as deescribed
Engine started

Paulus

#20
Just changed the fuel filter(getting ready for the North Channel)opened the knurled knob and started the pump for a few minutes and waited for the pitch of the fuel pump to change, closed the knob and started the engine.  This was on the hard and sitting all winter.
Just as Stu has described.
Cool Change 1989 #944

Catalina007

Ive changed the filters many times and never had to bleed anything it woud start right up.
Now, my electric pump runs at the same speed always.  It dosnt pressurize the system and slow down.
Woudnt this make sense as it would just be recirculating, effectively polishing, back to the tank via return lines?
 
 

Ron Hill

007 : I'd check all of the hose connections from the fuel tank, Racor, Electric fuel pump, engine filter, injection pump to the input to each injector.

That electric fuel pump pulsing should slow down as the fuel lines are pressurized !!

A few thoughts
Ron, Apache #788

Catalina007

yes i agree. But does the electric pump pressurize just to the bottom of the injector pump? O :sleepy:r through the injector pump and to the injector banjo return lines?

sorry to be so pedantic - just trying to understand the system and everyone has a different theory.

Ron Hill

007 : I believe that the electric fuel pump only pressurizes to the injection pump. Then the injection SUPER PRESSURIZES the fuel to each injector based on the timing.

A thought
Ron, Apache #788

KWKloeber

Quote

Functionally then I can't answer specifically how it works.  All I know is that nothing should ever come out anywhere near that assembly when you open the nut/Knurled Knob.  Somehow it introduces the fuel and air into the injector pump but if you follow the Bleeding 101 steps using the knurled knob and the electric fuel pump you will get all the air out of the system.

Perhaps someone who is more into the guts of the details of this assembly would chime and and explain it to and for us.



Happy to.  The knob and teat on it bleeds the fuel train BEFORE the I.P.
Early M25s had a bleed SCREW, that when opened would need fuel all over the engine if not done carefully.  Later M25s (and XPs) switch to the knob and return the bled fuel to the return line.

I posted many times that (IMO) that is a stupid arrangement because one cannot SEE the fuel that is being bled (foamy? dirty? strong stream? weak stream? what is it?).   
I switched to the knob (from the OEM screw simply for ease) but do not bleed to the tank I just catch the fuel in a cup when I bleed.  Then I know the condition of the fuel.  I've recommended many times that peeps with the Universal setup switch it -- (IMO only) it works better and makes more sense.
Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Explore.  Dream.  Discover.   -Mark Twain