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Several times when I've had less than 200 liters of fuel in the tank I've removed the inspection port covers to look inside the tank. I've never emptied the tank completely.
What I can also say is that when I changed the racor filters and opened the valve to refill the bowls on each side that the fuel flowed very freely from the tank to the racors. So I don't think that there was any obstruction there.
I do have the wiring for the water detector on the Yanmar fuel filter, but I've never drained any water from that fuel filter, or from the simple drain on the bottom of the Onan fuel filter, or seen any water in the Racor bowls (which is the first place that I'd expect to find water, and I inspect pretty regularly).
Thanks for the extra recco's.
Best regards, Daniel Carlson, on sv BeBe, SM #387
Did you ever check the filter inside the fuel tank?
Kimberlite Amel Super Maramu #376
Thanks all for the helpful tips which also provides great emotional support :-) Nothing like a hick-up with your main engine out at anchor to get a little anxiety up.
I changed both racor filters which had both been used since last changed. The in-use racor had noticably more dirt on it. I also changed the fuel filters on both the Yanmar and Onan as they were right at a year since last change and the Yanmar had over 400 hrs due to above normal use on the long haul from the Caribbean to Chesapeake Bay in May and back after hurricane season this November.
Both engines started and ran fine.
I can suspect that a lot of extra motoring/motor-sailing, often when beating to the windward could have contributed to added gunk load on the fuel filters. Also, in the last couple months we have had six rollicking reaches back and forth between Antigua and Barbuda with only about 200 liters sloshing around in the fuel tank. They were all sailing except the final 45 min to an hour using stirred up fuel to get into the anchorage. And the we just refueled last week as well, immediately motor-sailing for over a hour around to our anchorage. Plenty of reasons to stir up the tank and add load to the fuel filters.
- there were no issues with the Onan (but now with the LiFePo batteries it only had 100 hours over the last year and I'm sure that will go down more with my added solar capacity)
- no signs of water in the Racor bowls, or fuel drained from either the Yanmar or Onan fuel filters.
- Fuel filters are Racor, Yanmar and Onan OEM parts.
- last month when I was down to about 180 liters in the tank, I opened the rear tank inspection port and could clearly see to the bottom of the tank and it was clean stainless steel. Could still be a little gunk in the corners or far forward.
- I have been using Howes fuel treatment the last due refuelings, as well as a Valvetech biocide since Cartegena in Jan of 2020 (due to concerns with the hot humid environments we we're sailing in and also concerns about potentially having to purchase fuel with some bio-diesel in it)
- changing the Yanmar fuel filter is one of my less favorite maintenance tasks. Yes it's pretty straight forward and thanks for Bill Rouse simple instructions, but it's always a bit messy and I don't like the smell of diesel in the engine room.
- right now I'm chalking it up to restricted fuel flow due to dirty filters, but I guess that I was surprised to see it show up suddenly at idle.
Daniel and Lori Carlson on sv BeBe, SM #387, currently in Antigua
I don't have any amazing magic things to add to what others have said, but I would STRONGLY discourage you from fiddling with the idle speed adjustment on the injection pump. The inability to run stably at normal idle speed is a symptom, not the first cause of a failure.
This is not like the mixture adjustment on your outboard carburetor. It does not control the fuel flow itself, rather it controls the set point of a speed governor than then in turn adjusts the fuel rack. Adjusting the idle speed adjustment is not typically done as part of a repair, but is part of the set up of the injection pump.
If you can get the engine running at a stable speed (slower is easier for this test) it might be worth opening the nut on the injectors, one at a time. When disconnected, each injector should have a similar effect on the speed/smoothness of operation. If one has little or no effect, then that injector is likely bad or clogged.
Another trick that can help sort out things, put a piece of clear plastic tubing into the system just before the lift pump. If you see bubbles flowing by when running then you know you have an air leak that needs fixing. If you see only clear fuel flow, then you can check off everything upstream of this as OK. With your fuel tank nearly full, I doubt this is the problem, but it helps to be sure.
Last thing, I might have missed this, but if not yet done, changing the secondary fuel filter on the engine would be a good idea. Again, not a likely, but a possible, cause of this kind of problem. For this filter, I would recommend (if possible) using a Yanmar OEM filter. Some of the aftermarket filters have smaller elements and add excess restriction to fuel flow, especially after then get a bit of dirt in them. Normally problems with this filter are seen at high speed, not idle, but you have checked most all the easy boxes, so the less likely ones are what is left.
Tracking down fuel system issues like this can be a pain, but it will work out.