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Old 07-11-2016, 05:56 PM   #1
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Generator air leaks under load

Hi All. Had an interesting experience with both genset this week as we are away on a week long trip on he boat.. We live on our 70ft boat so all systems are exercised regularly. But the genset are not run under full load...just part load. So this week when running under full load pulling 30 amps they both developed air leaks.

The port genset leaked through the on engine filter o ring. Then again through the racor top o ring then again through the drain assembly and finally through a new washer on the new priming plunger pump which I recently replaced. I removed the washer and all good now. So multiple leaks but minute yet enough to show up when fully stressing the system.

The starboard genset leaked through the priming pump as well. I have ordered more replacements of this little hand plunger pump. I find they always fail. But are cheap to replace.i had already rebuilt this fuel system except for that part...

Anyway all working now but amazing how testing at dock shows nothing yet in real world application the faults show up.

Other than this and a bit of bad connection to the raymarine gps and losing fix it has been a good trip.
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Old 07-11-2016, 10:42 PM   #2
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Don't think you have addressed the cause, only the symptoms. Either under half load, so little fuel is used that all the air leaking into the system went on through without effecting the generator, or there may be another problem requiring the lift pump to increase vacuum which showed symptoms in the form of new air leaks. Do you have a vacuum gauge on the Racor? Symptoms might be from a dirty filter or a partially blocked fuel line. All those vacuum leaks at the same time seem to coincidental to me.

Ted
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Old 07-11-2016, 11:26 PM   #3
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Yes. Replaced filters and have run at max load for hours both motors different days. All sorted.
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Old 07-12-2016, 06:12 AM   #4
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Not to beat a dead horse, but the lift pump volume and vacuum level doesn't change with load. The generator is a constant speed engine, so no performance change for the lift pump regardless of load. Did you determine that one of the filters caused the problem?

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Old 07-12-2016, 06:17 AM   #5
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Thanks and I appreciate the input.

The racor had a hardened o ring. So replaced filter which was fine and o ring at see time. I also checked the drain on the racor and it would not tighten at all then started dripping fuel. It then broke so not having a spare I glued it together rock solid till I order a new one.

The on engine filter o ring also hard and there was the main leak there. When I replaced that filter it fixed it.

The priming plunger leaks badly when priming fuel. So I replaced it and no leaks now.

All going fine again today...hope it stays that way.
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