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Old 10-25-2016, 05:50 PM   #1
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Onan 20Kw generator- fuel leak at the fuel filter

the odd looking rectangular fuel filter....leaking drops from the bottom. I replaced these with new filters just 40 hours ago....but it's been over a year and now can't remember if I watched it after changing to make sure no leak....but pretty sure I did.

I have two of these...one is leaking pretty bad....constant drip, drip, drip when running....the other is perhaps a drop every 20 seconds...from same location on the filter...bottom right.

Any idea if perhaps I didn't seat the seal quite right or is this a common problem with Onans of this vintage (1993) ?
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Old 10-25-2016, 06:32 PM   #2
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Hmmm...can't say I've ever had a problem with them leaking.

Could the filters have been sitting around a long time before you used them and the seals dried out?

Or the sealing surfaces were contaminated with old gasket/o-ring material when you changed them last?
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Old 10-25-2016, 06:44 PM   #3
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I'm not at all familiar with these specific generators. But if the filters are leaking.... did you swab the seals with fuel prior to installation, or were they installed dry? If installed dry, that might explain it. But I'm poking in the dark here.
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Old 10-25-2016, 07:20 PM   #4
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Quote:
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Hmmm...can't say I've ever had a problem with them leaking.

Could the filters have been sitting around a long time before you used them and the seals dried out?

Or the sealing surfaces were contaminated with old gasket/o-ring material when you changed them last?
I did use filters that were in the boats spare parts inventory so lord knows how old they were. I vaguely recall they were sealed in plastic, but not sure...definitely new but don't know how old they were.
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Old 10-25-2016, 07:28 PM   #5
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Those filters are the same as used on late 80's GMC pickups with 6.2 diesel and Stanadyne injection pumps. Same mfr pump on the Onan. Should be able to get filters at NAPA, etc.

Can also leak at fittings to the filter base. Try to isolate exact source of leak. I think just rubber grommets form the seals, maybe they aged out and got brittle.
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Old 10-25-2016, 10:16 PM   #6
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Never seen a 20kw Onan so this may be entirely irrelevant. My Onan MDKD 6.5 fuel filter screw on thread faces upwards. It would screw on and not leak when run immediately after, but would leak badly later. After several filter replacements, and some tightening, it turned out the receiver fitting was the culprit, replaced it, no more problem. I suspect the damage came from an initial overtightening by a PO. With a similar arrangement, or even a side on fitting, you`d see fuel drip from the filter, but it`s not the filter body that`s leaking.
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Old 10-25-2016, 10:30 PM   #7
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Got a pic?

I saw some excellent suggestions for the normal leaks.

Off the wall, but possible, is electrolytically, chemical or galvanic corrosion. A drip from the same spot suggests a damaged sealing surface.
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Old 10-26-2016, 04:35 PM   #8
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Another possibility is that the old seal came off the filter and remained stuck to the filter housing. Then when you put the new filter on you ended up with stacked seals. That can definitely lead to leaks.
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Old 12-14-2016, 06:04 PM   #9
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Can also leak at fittings to the filter base. Try to isolate exact source of leak. I think just rubber grommets form the seals, maybe they aged out and got brittle.
Finally dealt with it today, the leak was a definitive smoking gun from the brass compression fitting behind the filter...not leaking at the filter itself...but the leak from the compression fitting dripped on the back of the filter and down from there, thus creating the illusion it was from one of the two round filter seals.

The compression fitting was surprisingly loose...pesky generator vibration I guess.
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