Secondary Fuel Filter Replacement

[Stevan47]

Hi all: I am just about to change out the secondary fuel filter of my 3YM30 engine in my R21-EC. As you would know, the secondary filter is situated on the stbd f'rd side of the engine, just above the injector/feed pump. This will be the first time I have changed the filter and I just want to ensure I do it right. Not exactly rocket science, I know, but as they say, ' no such thing as a stupid question'. I don't have a special tool to unscrew the filter bowl, so I propose dislodging it first with a couple of sharp,firm blows with a wooden dowel and small hammer, then unscrewing the rest of the way.

Once removed, cleaned up and ready to reinstall with a new filter element, I will then fill the bowl with clean fuel and rescrew it back on to the body of the filter assembly. All good so far.

The main question I have is: do I also need to loosen any injector lines and bleed the system of air, or will operating the hand pump vent lever do the trick for me? I am aware that the injector pump system is a self-venting system once running, but as my boat lives on a trailer when not afloat, I can't really start the engine to see if this does the trick. I have read the operation manual and it merely mentions using the hand pump to vent the system of any residual air.

Would appreciate your collective advice.

Kind regards and fair seas.

Stevan

 

[Kaisardog]

I am no expert on the YM yanmars, but have some ideas:

yanmar makes not only the thin little operators guide you got with your boat , but also a service manual, an install manual, and a parts manual. these are the best $80 you will ever spend . they give very detailed instructions about all of the questions you have. the parts manual, as it shows blowup diagrams, is particularly helpful if for example you are trying to figure out how to take apart your heat exchanger to clean the tubes.

as to the Yans, my manual says.. ' anytime the fuel system is e exposed to air the accumulated air will have to be bled from the system..' usually there is a priming lever on the feed pump to push air out. on our 2Gm3F and 3JHE's , operating the little prying pump laboriously did indeed bleed the air out. our manual says ..

to bleed air from the system proceed as follows:
1. loosen air bleed screw at top of s secondary filter between lift pump and injector pump..
2. when operating the priming lever on the pump be sure to push down completely to ensure full operation of the pump. Operate priming lever until fuel free of air flows from the air bleed screw, then tighten the screw.

only if air has gotten into the injector pump do you have to loosen lines on t he injectors ONE TURN then crank the engine to bleed air (on my models).

NB air can be drawn into the fuel system from a faulty bleed screw washer. yanmar recommends replacing the washer if you've bled the system because this loose 25 cent washer can really cause trouble. yan also says 'DO NOT over tighten the bleed screw, it is hollow and can break. '

3. 'if the high pressure side has been opened you will have to bleed the injector pump, injector lines and injectors. '
to do so (on my models) you loosened the bleed screw on the injector pump and operated the priming lever on the lift pump until fuel free of air flows from the bleed screw, then tighten the screw,,,'

4. then loosen the injector line nut ONE turn . if the injector has a hex spacer nut, hold the nut stationary with a wrench while loosening the line nut. (DO NOT try to loosen the line by turning the spacer, it will twist and wreck the fuel line , very expensive and messy to fix.)

5. place engine speed to full throttle, using the starter, crank the engine until air bleeds from all lines and fuel runs from the connections. then tighten the nuts securely...

another place you may check is boat diesel.com this is a website where owners of diesels can go to get answers on various engine issues. it is one of the best bargains in the family boating budget at $40 a year, which allows you to post questions to be answered by kind expert mechanics on your particular engine. you can pursue for free, search boat diesel.com then tab to yammers .

good luck and let us know how it went

 

[tuggertoy]

While Kaisardog has posted some good information, the simple answer is no you shouldn't have to bleed any air from the system.

Having changed this filter many times on my 3YM20, filling the bowl with fresh diesel before installation should allow you to start the engine. It will stumble a little as the small amount of air is eventually drawn through the system but should pick right up again once it has cleared.

Running the engine on the trailer is possible but I don't have time to detail the process right now. If you run the engine in the water for the first time after a filter change make sure you stay tied up until you are sure the engine is running properly. You don't want to experience an air locked engine a mile from the dock should that actually happen.

Eric
Tugger Toy
2006 R21 Classic

 

[Stevan47]

Kaisardog and Tuggertoy: many thanks for your kind and comprehensive advice. Good to know there are such knowledgeable guys out there. I will bear all your hints in mind and let you know the result once I have done it. Kind regards to you both from Down Under. Stevan

 

[Stevan47]

Secondary filter changed and system vented using the lever on the fuel feed pump. No issues - engine ran well on first trip post-change. Another successful 'maintenance availabity period'. Thanks to all for your advice. Regards, Stevan

 

[Kaisardog]

some late added thoughts on the filter change and bleed:

1) the little manual pump used to have a resistance about 1/2 way thru the stroke, often folks would not depress the lever all the way thru this detente , and thus could not successfully bleed ..

2) don't over tighten the retaining bolt on the secondary filter top. if you do you it strips the threads and you may have to buy a whole new assembly....

 

[Stevan47]

Thanks for that little gem. Also, as you said, there is some slight resistance when depressing the hand priming/bleeding lever. I depressed it all the way and everything worked well. Kind regards