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Old 03-05-2015, 01:54   #31
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Re: How does self bleeding work?

Self bleeding means I do it myself!
On my 2gm20 I use an outboard motor fuel line with a priming bulb before the lift pump. Squeeze the bulb to prime and bleed with the bleed screws. Much easier than using the lever on a manual pump. An electric pump might be even easier.

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Old 04-05-2015, 20:35   #32
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Boat: 41' yawl
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Re: How does self bleeding work?

Originally Posted by Jd1 View Post
If you have air in the high pressure lines then your injectors will not fire. Air is compressible, diesel isn't - you can not build sufficient pressure to fire the injectors with air in the lines as the amount of diesel pumped by the injector pump is small. The pressure goes up a bit but the air compresses and acts as a cushion. The pressure can't get high enough to fire the injector.
Man this is difficult to explain considering how simple the concept really is!
As far as self bleeding, I can only speculate that the high pressure pump is fed by the electrical lift pump and will pump it's tiny volume as long as there is fuel on the pump input. The output pressure will be too low to fire the injectors but fuel flows through the fuel return system back into the tank which flushes air out of the system. Once sufficient air is removed the injectors fire.

I think we have a winner. Makes sense, thanks!

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Old 04-05-2015, 20:46   #33
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Re: How does self bleeding work?

Originally Posted by boeing1 View Post
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.
Please be aware that many engines are wired to have the fuel pump ONLY run when the glow plugs are ON or the oil pressure is "made."

It requires a bypass to get the fuel pump to work when bleeding, and, IMHO, is a stupid way to wire the system, but that is what many folks have.

Mine is like yours on the fuel pump. We discussed it at great length on our C34 forum, since our Mark II boats with newer M35 engines came this way, while the older boats like mine, are simpler with an always-on fuel pump through the ignition switch, not the glow plugs.


However, on mine, the very LAST thing to do is to have to push BOTH the start and glow plugs at the same time. Makes NO sense. No reason to have both draw. I glow plug release then hit start. I installed a solenoid for the glow plugs, which come pre-installed on newer engines.

There are all sorts of different ways to do things, like it or not.

The trick is to learn what you have, how it works, and what to do with it.

Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, (Maple Bay Marina) SR/FK, M25, Rocna 10 (22#) (NZ model)
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