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Discussion Starter · #1 ·
Does anybody recognize this as the bleeding screw on the yanmar 3gm30f ?

If yes is it necessary to bleed this screw when bleeding the system ? and how much should it be turned for bleeding ?
 

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The bleeder is located near the centre of and on top of the secondary fuel filter. It may have yellow paint on it. Back it off until fuel comes out and no more.
Depending on how you are introducing pressure, ie; via a priming pump or by turning the engine over. The engine will start to fire up or the fuel will be free of air.
Retighten the screw after the engine fires or after no more air is noticed.
If you are changing out the fuel filtre's I prefer to warm the engine up before taking the old filtre's off.
A warm engine is easier to start than a cold one.
 
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Discussion Starter · #3 ·
Thanx for your reply. The manual says that the bleeding screw on the fuel i jection pump should be bleeded too. Do you bleed only the bleeding screws on top of the Primary and Secondary filter ?
 

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Thanx for your reply. The manual says that the bleeding screw on the fuel i jection pump should be bleeded too. Do you bleed only the bleeding screws on top of the Primary and Secondary filter ?
The only one I have had to bleed is the I mentioned. It might depend on what your doing, All I have done with my motor is changed the filtre's.
 
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You are correct, that is a bleed screew. Should not need to bleed this point if all you did was change the filters. If however you managed to run out of fuel then this will need to be bleed as well. You may even need to bleed at the injectors.
 

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Basically there are (3) bleed points on a Yanmar 3GM30F. Working from the low pressure side there is a bleed screw on the primary fuel filter, second there is a bleed screw on the high pressure pump(as shown in your attached pix) and then there is/are the bolt(s) that connects the fuel rail to the individual injectors. Usually the first two bleed points are generally used after fuel filter(s) replacement.

Sometimes if there has been alot of air ingested possibly from changing both fuel filters..if one has a water/fuel seperator like a Racor.. there is a good chance that one has to open the individual high pressure injector bolts that hold the high pressure fuel rail inorder to get the last bit of air bubbles out of the high pressure pump.
 

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I change both my primary and secondary fuel filtre's once a year. I have only had to use the secondary filtre's bleed screw to evacuate the air for this procedure.
The Racor can be drained of it's water and debris with the engine running.
 
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Discussion Starter · #8 ·
Thanx a lot for your replies.

I will change the filters, bleed the on the primary filter and secondary filter. If that does not work I will have to try to bleed on the high pressure pump too and potentially the injectors.

Suppose I will to need bleed only the higher of the bleeder screw on the secondary filter and the high pressure pump
 

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If you do bleed both filter bleed screws, bleed the primary first and then the secondary filtre's bleeder. If you do it the other way around you will just introduce more air into the system again.
That's why I only bleed the secondary as it is after the primary filter and this will evacuate all the air that has been introduced into the system. It also helps to fill the filter canisters with fuel before reinstalling them.
You shouldn't have to bleed the high pressure end of the system unless air has made it's way in there somehow by running it out of fuel, trying to start it without bleeding the filtre's first, or by having worked on that part of the fuel system, etc.
If it's just a simple change of filtre's and you have not done "anything" else you should be ok by just bleeding the secondary's bleeder.
 

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May i suggest that for your own piece of mind that you bleed to the high pressure pump using the primer pump, every time. Not only to ensure that all the air is vacated but also to eliminate the need for having to bleed the high pressure side if you do happen to get air in it. First to the secondary filter head, then to the h/pressure pump bleed screw you pictured. It's good practice, and with practice you will further your mastery over the basics of engine maintenance. A suggestion to further your mastery is to not bleed the low pressure side by cranking the engine because although the high pressure pump does not have the ability to pull fuel from the tank, it can pull air as it pumps but it does not have the stroke to efficiently compress the air and force it out past the nozzle. You would then have to bleed the air at the injectors using the cranking engine to do so.
 
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