Sailinghartu - I read a lot of these
forums, and used to
work on engines, now spend more time advising on installations these days, although generally not in a
marine environment, seems the
Yanmar lift pump, can fail in a few ways,
1) leak
fuel externally.
2) leak
fuel to the crankcase.
3) allow air into the fuel.
Like any part of the fuel system air can get in even if fuel cannot get out, the
pump will have a
diaphragm, inside so won’t last forever.
I always ask myself - is it really needed? Because the more things you fit the more you have to fail. Sometimes adding something that you think is good can actually drastically reduce the system
reliability.
Generally I would consider removing a mechanical fuel
lift pump, where ever possible. No matter of the manufacturer also in some cases a lift pump is not even required. Which is a much better solution.
That said I had an
Electric lift pump on my Beta, and had a fuel issue in an estuary ( had to run to the bow and throw the
anchor out - things never fail when you are in a safe place) anyway I replaced the filters and removed the lift pump, and had no issues since.
If you see also about pressure testing your fuel system with air and using soapy
water to check for
leaks like you would with a Gas pipe. You only need to add a low pressure and a gauge. I have never had to do this myself on a
diesel system ( mandatory on Gas ) but I have strongly suggested that others to carry out this test, when they cannot fix their issues.
Yanmar Still one of my favourite small engines.