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Old 12-01-2016, 16:45   #1
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New filter, getting 10" of Hg

I just changed my primary filter element and put one 10 micron one (at least that's what I believe it said on the filter). I also installed a vacuum gauge between the primary filter and the lift pump. I then started up the engine, and the needle on the vacuum gauge is going back and forth between 0 and 10 inHg. It's going back and forth so quickly that it's almost hard to get a reading, but I guess this is expected since a vacuum is created each depression of the lift pump. However, the 10 inHg is higher than I expected.

My motor is a Yanmar 2YM15.

This is the vacuum gauge that I got.
Interstate Pneumatics G2024-030V 2 -1/2 Inch 30 PSI - 1/4 Inch NPT HG Vacuum Pressure Gauge - -

I appreciate any help.
asahi is offline   Reply With Quote
Old 13-01-2016, 09:57   #2
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Re: New filter, getting 10" of Hg

Without knowing the brand and model of your primary filter, it is difficult to comment of the level of vacuum you are experiencing, however a quick look at the vacuum gauge which is available from Racor Filters for their turbine series might give you a base line for further action. The Racor gauge gives from 0 to 7" of mercury as an acceptable level of vacuum, from 7" to 10" of vacuum as being in the yellow segment of the gauge, and over 10" of vacuum as being in the unacceptable "red" section of the gauge.

Looking at the Racor information for their spin-on filters, the typical maximum new filter vacuum is about 1" hg.

All this points to your vacuum level as being rather high, but with a wildly oscillating gauge needle it is really impossible to tell what you have. What you might try is to install a restrictor between the gauge and the vacuum source to dampen the pulses. A fitting with a drilled opening of about .015" or .020" might work, or you could install a fluid filled gauge as Racor uses.

Hope this gives you something to think about.

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Old 14-01-2016, 00:42   #3
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Re: New filter, getting 10" of Hg

A liquid filled gauge will soften the pulses and last longer. Use them anywhere there are strong pulses, like behind a pump.
As a guide, I have Racors with a 4 micron primary feeding 2 Detroits and a Perkins generator. About 80 gallons an hour cycle thru the filter. With a new filter, my gauge reads 0. When it gets to 10, I change it.
Why my primary is a 4 micron is a long story, but I buy clean fuel and my tanks are kept clean. My secondaries never get dirty, but I change them about once a year.
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