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Discussion Starter #1
Hi, I have a yanmar 3gm35f engine. I want to make sure that I have a correct fuel filter changing procedure in place, primarily to avoid getting air in the fuel lines. Any ideas where I can find it? My engine manual doesn’t cover it. Here is a picture of the filter housing.
 

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The Yanmar in our generator requires no manual bleeding. It has a fuel shut off at the filter housing and an electric fuel pump that refills the housing.

The process for our Volvo Main is a tad more involved, but often get away with not bleeding. Not always.

The point is, they’re all different. Find the operator manual for yours. It’s good to have for lots of reasons.
 

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We have a Yanmar gmf30. Similar engine . As long as we fill the Racor to the top with diesel it usually does not involve bleeding.

We always have a small jug of diesel as well as cup with pouring spout to do this as we change our filter at least once in season as well as before winterization.

That being said, you should identify and semi practice how to bleed your injectors. It’s not a hard thing to do. 😀
 

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That looks more like a fuel/water separator with possibly a screen in it to filter out the big stuff. If you have a Racor 500 as your primary, you shouldn't need to bother with the secondary every 3rd or 4th Racor filter change, unless you have water in the Racor bowl.
It appears you have a fuel pump directly before this filter. If you fill the Racor is full and this bowl, you should be able to bleed the system at the injectors, as above. Just lay an oil absorb pad under the injector feed lines and crank the engine until raw fuel without bubbles comes out at the injector feed line/injector connection (nut).
However, also as above, you may not need to bleed the system at all if you fill the fuel filter housings up all the way.
 
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Discussion Starter #5
Thank you for your advice. This is a fine polishing filter past the Racor filter, just before the injection pump. Racor is mounted much higher. I have changed the Racor filter but not this one. I have noticed a tiny fuel leak there. I tightened the filter Cup and the mandolin connectors bringing fuel to and from the filter unit. Electric pump pumps the fuel to this unit. I looked in the manual but the filter changing procedure is not there. These are small pleated paper filters that I have on hand. I’m currently on hard in Brown’s Boat Basin in Nassau for a few more days. Would like to get that done before I leave to go south.
 

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Kriss,
Just fill the secondary filter with diesel as well as the primary as Chef2 suggested and you shouldn't have to bleed. If you do have to bleed, start with the bleed screw on top of the secondary, the one that uses a 10mm wrench. I have only had to bleed at injectors when the engine stalled due to clogged filters and as others have said it's no big deal. If you're doing it by yourself you will need to short the starter solenoid with a screw driver unless you have a remote start switch. Start at the forward injector and turn the engine over till you don't see any air, Move to the second and repeat. Engine will most likely fire after the second injector is bled.
After Thought....
When I say fill the secondary filter I'm talking about the bowl that the paper fits into. You should also change the O ring on top of the bowl when you change the filter.
Hope this helps
 

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If you're in a pinch and need to get this done, without the manual, here are some methods...... Which is yours, I can't know. Isn't the operator manual online somewhere?

Does your fuel pump have a manual lever on it? Many/most mechanical pumps do.

If it does, shut off the fuel at the tank or wherever you can prior to the filter. Remove that ring with the grooves that is holding the bowl on. The grooves can be moved by tapping them, in the proper (lefty loosey, righty tighty) direction, with a screwdriver and hammer, as necessary. Pull the filter housing off, drain it's fuel into something you can see to inspect for contaminants. Clean the bowl and replace the filter. To replace, you can first try to fill the housing, either partially or fully. However, in many installations, you need to tip the housing to get it back to it's mount, making that messy or impossible. I don't bother, on the engine mounted filter. Push the housing back on and tighten the ring you originally loosened. I typically tighten about 1/8th turn past hand tight. Don't over tighten. Be sure the gasket seats normally and is not pinched. Now loosen that nut in the center, on the top of the filter mount. It should be the bleed screw for the filter housing. This is different than bleeding the injectors. Start pumping the manual lever on the fuel pump, until you stop seeing bubbles and see pure fuel come out. I can't reach the lever and watch, at the same time, so I put a paper towel over it and wait for a good slug of fuel. If you are not seeing bubbles or fuel, it's because the cam is not in a position to allow the lever to actuate the pump. You have to tap the starter and not let it try to fire, just to slightly move the cam and try again. Tighten the bleed screw. Turn fuel back on. Start engine. It may chug a bit and smooth out in a few seconds. If it won't start or continually runs rough, you'll need to bleed the injectors.

If you have an electric pump, removal and reinstall is the same. To refill the filter housing and prime the fuel lines to the injector pump, you typically just activating the ignition, without turning it to start. In some cases, with button start, you tap start, but don't hold so it actually starts. This powers the fuel pump which circulates fuel until pressure is achieved.

Of course, in either case, check the housing for leaks. The gasket can need replacing periodically. More often, it's not seated properly, if it's leaking.

If you're forced to bleed the injectors, it's pretty easy. You just back off the nut on top of each injector, until it's not being held by any torque. Don't fully remove. Crank engine, without starting, until fuel appears through the threads. It will get past, as the injector is pretty high pressure. Again, using a paper towel around it can help identify the fuel, if you need to go back and forth to the cockpit. Retighten the nut. Do the injectors one at a time.

That's the best I've got in the blind. Good luck.
 
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One other note:
DO NOT OVER TIGHTEN THE BLEED SCREW. If you're like me and have a tendency to tighten beyond snug be careful. The housing for the secondary is Aluminum and it's easy to strip the threads On it. Stop at snug.
 

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I sometimes had to use the bleed screw at the top of the filter, sometimes not (2GM). Sometimes it would run just fine, a couple of times it ran rough for a bit... Towards the end I just always bled it from that screw. Always have the crush washers on hand if you don't want things to weep.
 

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This is a fine polishing filter past the Racor filter, just before the injection pump.
That filter is just the OE Yanmar filter as you would find on a tractor engine. They are 10-15 micron rated depending upon the Yanmar supplier they ordered from. Changing them is simple.

Shut off fuel at tank
Stuff some rags under the filter bowl
Unscrew the knurled ring
Drop the bowl
Replace the filter and o-ring
Put it back together

To bleed simply loosen the top screw on the housing and prime the manual pump lever on the fuel pump. Do have the crush washers on-hand for bleeding as they often fail to seal after bleeding the on-engine filter.
 

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Discussion Starter #12
To bleed simply loosen the top screw on the housing and prime the manual pump lever on the fuel pump. Do have the crush washers on-hand for bleeding as they often fail to seal after bleeding the on-engine filter.
Thank you, sir. That is where the leak was: under a crush washer.
 
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