Have a Yanmar 3gmf and just replaced all fuel lines. Added a Racor filter and changed the the engine mounted filter. I am now chasing an air leak in the fuel system. It will run but stalls. I have a few ideas but wondered how tight the filter bowl at the engine needs to be. I can't really get a tool on it to tighten it. Right now it is hand tight.
Yanmar 3gmf
- Thread starter a65sailor
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I can be tightened with a piece of hardwood that you place on one of the cogs of the cover and hit lightly with a small hammer. Be very careful as it is aluminum and you might break it. I have a 4" inspection port on the startboard side panel and can slide in a pair of channellock plyers. Again careful with these. However, since you changed all the fuel lines, your problem could be at one of the banjo washers. An air leak should also show a fuel leak. Me thinks you still have air in the system and the engine needs to be bled, starting at the newly installed Racor and working your way up to the Yanmar filter, then the injection pump (if needed) and finally the injectors (again if needed). If you have the 3GM30F engine, enlist a friend to hit the starter button after you have decompressed the engine. It builds pressure much faster than busting your finger on the pump lever. Don't forget to shut off water intake while you do that as you do not want water ingestion because of lack of exhaust pressure. Good luck
All good suggestions. I have been chasing an air leak on my 3GMF (only shows up when using the engine for 5+ hours at a stretch) for a while now and would offer the following:
In order to trouble shoot your issue I would start at the Racor and work forward. If you get air in the Racor, then it's either the Racor (o rings etc) or something between the fuel tank and the Racor. Address those points and run the engine. If the problem persists and the Racor has no air in it, then check the Engine mounted filter. If it has air, check all connections between the Racor and the Engine mounted filter. work your way along the fuel system in this manner until you find your issue.
Cheers
MAtt
In order to trouble shoot your issue I would start at the Racor and work forward. If you get air in the Racor, then it's either the Racor (o rings etc) or something between the fuel tank and the Racor. Address those points and run the engine. If the problem persists and the Racor has no air in it, then check the Engine mounted filter. If it has air, check all connections between the Racor and the Engine mounted filter. work your way along the fuel system in this manner until you find your issue.
Cheers
MAtt
Before and after the lift pump
When troubleshooting air in the fuel system I always thought the following to be true: The engine lift pump sucks fuel from the tank, through lines to the Racor and then to the pump itself. Any loose fitting, clamp, etc. in that part of the circuit will allow air to be sucked into the system. After the lift pump, the fuel is pumped, under pressure to the secondary filter, injector pump and injectors. Any loose clamps fittings, etc. are more likely to show a fuel leak rather than admit air into the system. Perhaps an over simlification but it has always worked for me.
When troubleshooting air in the fuel system I always thought the following to be true: The engine lift pump sucks fuel from the tank, through lines to the Racor and then to the pump itself. Any loose fitting, clamp, etc. in that part of the circuit will allow air to be sucked into the system. After the lift pump, the fuel is pumped, under pressure to the secondary filter, injector pump and injectors. Any loose clamps fittings, etc. are more likely to show a fuel leak rather than admit air into the system. Perhaps an over simlification but it has always worked for me.
You sure it is an air leak? I had the same symptoms last Sunday. I could run forever at 12oo rpm(2.25knots), and for shorter periods at higher RPMs before the engine would cut off. Sailed home and found water in the filter bowl. The filter did not look so good either. Added WaterZorb and topped off the tank and all was well.
If the above doesn't address the problem and you're sure it is an air leak (which can only occur upstream of the lift pump) open the fuel line as far back as possible. Elevate that point as high as possible, insert a small funnel, fill with fuel, and your air leak will now become a visible fuel leak.
If it is running and I open the bleed screw at the Racor will it bleed air or suck more in? If it will bleed air could I do the same thing at each of the bleed points until the system is air free?
Might work if the level of fuel in your tank were as high as possible (full tank) to ensure a positive pressure at your bleed points. Also, all fuel filters should be clean to ensure no pressure drops when the engine is running for this exercise..