Like many, I am getting air in my fuel system on my Yanmar 3GM30F. First start of the day is rough but after that it starts at the press of the button. When left over night and I bleed the system I do get air bubbles and can feel a film of diesel covering the connections on the fuel filter hence I know there is not a proper seal there somewhere. In my eagerness to ensure that I didn't have this problem, I'm told that I may have originally over tightened the crush washers/banjo fittings. I cannot find any reference as to a torque spec in my Yanmar Service Manual. Does anyone have a recommendation as to how tight these should be?
Air In Fuel System
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I'm at that point as well (slight leaks and 12-13 yo washers) and willing to purchase a decent torque wrench if I know what the ratings are. The manual has general ratings based on size of nut/bolt but I doubt those are correct for fuel fittings.
Yan3GM30F..thoughts
"Like many, I am getting air in my fuel system on my Yanmar 3GM30F. First start of the day is rough but after that it starts at the press of the button. When left over night and I bleed the system I do get air bubbles and can feel a film of diesel covering the connections on the fuel filter hence I know there is not a proper seal there somewhere."
--are you getting the fuel sheen at your RACOR primary or your secondary on-engine filter? or on the hoses somewhere /
(some thoughts: are the hoses on your RACOR filter secured by adequately tightened hose clamps? many after market RACOR installers just woodscrew the filter into a backing plate, if the racor is loose on its mounts it weakens the connection for the input and out put hoses and air gets in there..)
(the on-engine filter is much less likely to have a loosen hose due to vibrations)(unless of course your engine mounts are worn... ie older than say 5 to 8 years.) )
-- you can take a pristine clean white rag and run it carefully from fuel tank exit to secondary on-engine, stopping every 2 inches to sniff and smell the rag. the first place your rag smells like diesel is a likely culprit for a pinhole leak in the fuel hose ESPECIALLY if t eh hose is making sharp down turns or bends fome tank to filter. if your fuel hoses are OLD just trash them install new and bleed the system. )
I find it odd that despite the fuel leak, the engine is rough starting then tends to run OK. taht fact tells me you s till have a pretty good engine-driven campump driving the fuel into your secondary filter. since there should be good clean fuel left in the injection nozzles after you shut down, this fuel should start up readily THEN the air bubbles come in a make it run rough...
hmmm i will have to hit the books on this one..
Mitch M , s/v Eagles Wing out of Erie PA
yanmar 2GM20F and Yanmar 3JHE
"Like many, I am getting air in my fuel system on my Yanmar 3GM30F. First start of the day is rough but after that it starts at the press of the button. When left over night and I bleed the system I do get air bubbles and can feel a film of diesel covering the connections on the fuel filter hence I know there is not a proper seal there somewhere."
--are you getting the fuel sheen at your RACOR primary or your secondary on-engine filter? or on the hoses somewhere /
(some thoughts: are the hoses on your RACOR filter secured by adequately tightened hose clamps? many after market RACOR installers just woodscrew the filter into a backing plate, if the racor is loose on its mounts it weakens the connection for the input and out put hoses and air gets in there..)
(the on-engine filter is much less likely to have a loosen hose due to vibrations)(unless of course your engine mounts are worn... ie older than say 5 to 8 years.) )
-- you can take a pristine clean white rag and run it carefully from fuel tank exit to secondary on-engine, stopping every 2 inches to sniff and smell the rag. the first place your rag smells like diesel is a likely culprit for a pinhole leak in the fuel hose ESPECIALLY if t eh hose is making sharp down turns or bends fome tank to filter. if your fuel hoses are OLD just trash them install new and bleed the system. )
I find it odd that despite the fuel leak, the engine is rough starting then tends to run OK. taht fact tells me you s till have a pretty good engine-driven campump driving the fuel into your secondary filter. since there should be good clean fuel left in the injection nozzles after you shut down, this fuel should start up readily THEN the air bubbles come in a make it run rough...
hmmm i will have to hit the books on this one..
Mitch M , s/v Eagles Wing out of Erie PA
yanmar 2GM20F and Yanmar 3JHE
I had a similar problem on a 2gm with hard stating after the engine sat for a few days. The main culprit was a check valve in the return line (it went from the injectors to a "T" and then to the tank and the injector pump).
Be super careful over-torquing your banjo fittings. They are easy to strip out. If you can't make them leak free with moderate hand pressure replace the washers.
--Tom.
Be super careful over-torquing your banjo fittings. They are easy to strip out. If you can't make them leak free with moderate hand pressure replace the washers.
--Tom.
Thanks to all so far. MitchM...The engine is a fresh rebuild with the injectors and high pressure pump overhauled and set up at the local diesel shop and all other lines, fittings and crush washers bought new which is why I suspect that I over tightened. Of course the fuel filter and hoses on the Hunter30 are on the side of the engine that is obscured from view and the aid of the wifes make-up mirror I can see some things. I did place tissues around the fittings and I can see small stains. I bought all new crush washers and ordered new bolts today as well(should be here Wednesday) and wanted to ensure I got the correct procedure before I install. On my last engine(YSM12) I ran into the same problem. On our maiden test ride, the boat air locked and shut down in the middle of a narrow channel near some really expensive boats. Guess who had no sails, no anchor, no radio, no cell phone......fortunately we drifted by a mooring which we scooped up and bled the system. Life teaches us so many wonderful lessons.LOL!!!! I'm not leaving dockside until the leak is sorted out.
My fuel tank does not have a return line. On the old YSM12 the return supply went back to the top of the fuel filter(same filter as the 3GM30F) so that is where I attached it. The local diesel shop said that it is a common return as there should be minimal fuel anyway. Any one have any comments on this modification for the 3GM30F?
My fuel tank does not have a return line. On the old YSM12 the return supply went back to the top of the fuel filter(same filter as the 3GM30F) so that is where I attached it. The local diesel shop said that it is a common return as there should be minimal fuel anyway. Any one have any comments on this modification for the 3GM30F?
Disconnect the fuel line input to the lift pump, then plug up the tank vent. Use your dinghy pump to pressurize the fuel system from the inside, use a paint brush to apply soapy water to all the connections. Inspect with a bright light.
Rick; I didn't know that crush washers had a torque value. It seems to me that once they start to crush the resistance goes down and you will nearly over torque them. My understanding was to tighten them until snug and then tighten them 1/2 to 3/4 of a turn. Anybody know better?
Let's hear it.
Joe S
Let's hear it.
Joe S
Yes, somebody knows better: Alan gave you a very valid answer. If you won't believe him, I don't know why you're asking anyone else.
Joe S asks a valid question...
after a number of years building sports car racing engines, I know better and still have at least one torque wrench. There's no way I could fit even a small torque wrench into an effective position on a fuel line banjoe nut in the close confines Hunter gave me to work on my 3GM30F, much less apply the correct amount of torque. (No, I don't have or use a ratcheting one).
As on car oil sump drain plug washers, finger tight and then no more than one face tighter with a wrench should be more than adequate to prevent leaking without stripping the aluminum threading. It worked for me when I overhauled my fuel delivery system with new washers a couple of years ago, with no leaks since. Just don't try to reuse the washers once they've been tightened down!
Joe, the 1/2 to 3/4 turn works better on an oil filter, however.
after a number of years building sports car racing engines, I know better and still have at least one torque wrench. There's no way I could fit even a small torque wrench into an effective position on a fuel line banjoe nut in the close confines Hunter gave me to work on my 3GM30F, much less apply the correct amount of torque. (No, I don't have or use a ratcheting one).
As on car oil sump drain plug washers, finger tight and then no more than one face tighter with a wrench should be more than adequate to prevent leaking without stripping the aluminum threading. It worked for me when I overhauled my fuel delivery system with new washers a couple of years ago, with no leaks since. Just don't try to reuse the washers once they've been tightened down!
Joe, the 1/2 to 3/4 turn works better on an oil filter, however.
Thanks Dan. I read Allan's post and was not trying to be a wise ass. I know that we all come from different experiences and are trying to give the best response we can. 20 ft lbs did seem excessive to me, but I wasn't sure. I had never heard of torquing crushable washers before so I thought I would mention my doubts.
Perhaps my 1/2 to 3/4 turns was also excessive but I'm getting old and rusty.
Thanks for the update and good luck Rick.
Joe S
Perhaps my 1/2 to 3/4 turns was also excessive but I'm getting old and rusty.
Thanks for the update and good luck Rick.
Joe S
Air Out
Just wanted to pass on thanks for the help and add my conclusion. Following everyones advice, it took four times of stripping the fuel lines off the secondary filter section and re-installing new crush washers at various tightness. Finally got peeved and cranked onto the one I suspected and the past two days had no residue around the filter area. It appears that the new fuel line leaving the seconday filter to the high pressure pump was not mounting flush against the filter face and because it is a solid metal and short line it has no flex and was stubborn about seating and sealing with the crush washer. A diesel mechanic at the Club mentioned this is a common "sore" spot on the Yanmar 3GM30F because the vibration of the engine transfers to the fittings and loosen them over time. He suggests to cut a few inches out, flair the ends and insert a flexible piece of fuel line. I will keep this in mind. We done 3 hours of sea trials yesterday without a burp. Hopefully I can close this chapter. So as suggested....there is no proper torque or tightness. Start snug and work it until it seals???????
Just wanted to pass on thanks for the help and add my conclusion. Following everyones advice, it took four times of stripping the fuel lines off the secondary filter section and re-installing new crush washers at various tightness. Finally got peeved and cranked onto the one I suspected and the past two days had no residue around the filter area. It appears that the new fuel line leaving the seconday filter to the high pressure pump was not mounting flush against the filter face and because it is a solid metal and short line it has no flex and was stubborn about seating and sealing with the crush washer. A diesel mechanic at the Club mentioned this is a common "sore" spot on the Yanmar 3GM30F because the vibration of the engine transfers to the fittings and loosen them over time. He suggests to cut a few inches out, flair the ends and insert a flexible piece of fuel line. I will keep this in mind. We done 3 hours of sea trials yesterday without a burp. Hopefully I can close this chapter. So as suggested....there is no proper torque or tightness. Start snug and work it until it seals???????
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