Bleeding air through Yanmar

[pmcrosta]

My efforts at routine maintenance have gone awry and I need some guidance.

I replaced 3 fuel filters (2 primary and one secondary) and am having trouble bleeding the system and getting her started again. I finally found the fuel lift pump on the starboard side of the Yanmar 4JHE, and have pumped vigorously trying to get fuel/air to come out of the secondary filter petcock.

Does anyone know how long one needs to pump this for? Should I loosen the injector bolts and pump as well? Does anyone know how much to prime the primary filters using the priming pump on top of the assembly? (The guidance in the Yanmar manual is not great).


The TLDR is below, and I've attached a photo of the primary filters (since I can't seem to find any info about these online).

Thanks in advance!

Long Version:
On Saturday, I changed two primaries and one secondary filter, but put them all back on without filling with diesel (and without bleeding). Then Started the engine. It ran for about 30 seconds using the existing fuel in the lines I guess, but then it died. Then we unscrewed all the filters and added fresh diesel. Then we opened the secondary filter petcock to bleed and opened one fuel injector to bleed. Tried starting it for about 20 minutes, and actually ran the starting battery down (this was Sunday). Then Monday, I tried two things. Each of the primary filters has a priming pump. So I pumped them for a bit. Then I found the manual fuel lift valve on the engine. I opened the secondary petcock and started pumping to see if i could get fuel out of the petcock. Nothing ever came out. I loosened a fuel pump bolt and saw some fuel come out. But nothing out of the petcock. I eventually tried cranking again and the engine started for about 5 seconds and died. So I think there is still air in there. I’m not sure how long I am supposed to pump the lift valve for or if I just need to unscrew all the injectors. (I also read about dangers of having the freshwater intake open while doing this, which I have, and so now I am worried about flooding the engine).

 

[Bill Roosa]

I was taught that you need to chase the air out of the system from tank to injector. Start at the first filter in the system and make sure no air is trapped there first. Move to the next and prime till no air come out. The next one should be after the engine feed pump so use the manual lever to get the air out of the inlet line on the next filter first then open the outlet line and pump till no air bubbles,........continue to the injector pump. Yanmars are self (sic) priming after the injector pump so you should be good after that.
As a general rule don't take all the filters off at the same time. Take them off in order of fuel flow to limit the introduction of air.
As to how much do you have to pump? Well if you filled the filter with fuel before you put it on and tried to keep air out to begin with you only have to pump a lot. if you are filling up the filter with the manual pump a lot is putting it mildly.
good luck

 

[Michael G]

The other thing about the 40.5 is that the fuel runs down hill due to gravity and on mine all i have to do is open the bleeder screw and the fluid itself always seems to push the air out. I always shut the fuel off at the tank while changing filter then open it up and let her flow. Good luck.

 

[splax]

One should fill the new filter and housing with fuel, if possible, when installing. An in line squeeze bulb is nice to have when priming. Open the bleed screws on the primary filters in order from the tank. After fuel leaks from the closer close it and continue to prime until fuel comes out the farthest. Don't worry about the bleed on the secondary, instead open the bleed at the injector pump. Priming then takes care of the secondary and the injector pump. After fuel bleeds at the injector pump, close it and use the starter for about 15 seconds at a time, with 1 minute rests in between, until the engine starts. The air in the injector lines should purge itself, but if rough idle is persistent you then need to bleed the injector lines. There is a procedure in your manual, I think.

 

[ice breaker]

With as many filters and valves as you have in this set up it may well serve you to install on inexpensive electric fuel pump close to the fuel tank that can be run to prime the system. This would give you the opportunity to work all the valves and get the air out of each filter and its connecting hoses. I assume that the 2 primaries are for a quick change over if one gets plugged.

I have an electric fuel pump on my panda gen set, with a push button to prime. When I change filters, and then push the button all the air gets purged very quickly. You can hear when the system is air free.

 

[VanIslandGuy]

With as many filters and valves as you have in this set up it may well serve you to install on inexpensive electric fuel pump close to the fuel tank that can be run to prime the system. This would give you the opportunity to work all the valves and get the air out of each filter and its connecting hoses. I assume that the 2 primaries are for a quick change over if one gets plugged.

1+ on this. On our old boat, the fuel tank was in the bilge well below the engine. There was approximately 6 ft of fuel hose to get to the racor. We plumbed in a walbro fuel pump between the tank and the bilge with a clear automotive fuel filter to protect the pump. Turning on the ignition but not to start was all that was necessary to get fuel pressure. Simply open the set screw over the blocks fuel filter with some paper towels ready until the bubbles stop. I could bleed effectively in 3 minutes.

I haven't changed my filters yet on our 410. That's another spring project on my list. Hopefully the higher position of the tank will eliminate the need for a fuel pump to get this done. Plus the 4Je is supposed to self bleed much better than my old 2qm motor.

 

[pmcrosta]

Thanks to everyone for your suggestions. Went down to boat today and started from the first filter closest to the fuel tank. I released the bleed screw on the Racor 200 assembly and pumped the priming pump until just diesel came out. Then did the same thing with the second primary filter. After, I opened bleed screw on secondary filter and primed it using the lift pump on the injector pump. Finally diesel came out of the bleed screw. Turned the key and it still didn't start. So I unscrewed all 4 fuel injectors and turned the key again, it didn't start, but I saw fuel and some bubbles leaking out. So I tightened them up (now everything is tight) and used the lift pump one more time.

Turned the key and she fired up!

I think there was just a ton of air in the system from my first start after changing all three filters at once. Rookie mistake, I am sure, but I wish this process was well documented in any manual anywhere on the vessel. This forum was a great help though!

 

[scottdube]

Nice Job!

 

[weinie]

I have a different Yanmar, but found that starting the engine after a filter change, letting it die after the air gets in, and THEN priming the secondary filter (I don't have a pump mechanism on the primary), I am able to get fuel to bubble out of the secondary filter bleed screw. It's weird, but it works every time.