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Old 11-19-2015, 04:30 PM   #1
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question: fuel filter vacuum gauge

I have twin 135hp Fords on my Marine Trader 38, and I am thinking about installing a vacuum gauge on the fuel filters. I don't need a remote display at the helm; just something to check in the morning before I take off. My original idea was to buy some $3.99 vacuum gauges on amazon and stick them on a T on the discharge side of my Racors. But, I see there are super duper gauges for the Racor T handle fitting that sell for $60 to $80. Is the super duper option really worth that much more money?

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Old 11-19-2015, 04:44 PM   #2
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Go to McMaster-Carr and get some liquid filled ones. The liquid dampens the pulsations from the lift pump. I bought some a couple of years ago, I think around $25.
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Old 11-19-2015, 04:50 PM   #3
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Vacuum is Vacuum, but use a decent gauge as BobH mentions. No need to do the Racor specific application. Mcmaster is an excellent source for all this stuff...

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Old 11-19-2015, 05:08 PM   #4
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the one on my boat works fine but it doesn't have a drag needle to hold the highest reading till reset. I think that would be handy.
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Old 11-19-2015, 06:03 PM   #5
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the one on my boat works fine but it doesn't have a drag needle to hold the highest reading till reset. I think that would be handy.
I have never messed with one of these vacuum gauges, but I would think that the vacuum would be the same whether the engine is running or not. Is this what you are seeing in your boat?
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Old 11-19-2015, 06:07 PM   #6
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IMO they are a waste of money for a low fuel flow engine like a Lehman. You rarely see any significant vacuum reading until the filter element is completely clogged up. Even then you may not see that much vacuum on the gauge.
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Old 11-19-2015, 06:08 PM   #7
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I have never messed with one of these vacuum gauges, but I would think that the vacuum would be the same whether the engine is running or not. Is this what you are seeing in your boat?
You would be 100% wrong.

I've always liked these guys' stuff, screw right into the Racor:

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Old 11-19-2015, 06:51 PM   #8
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If you install a gauge don't get the ones that go on top of the racors. When you change filters the Tee handle gets dropped. Slippery fingers diesel and all end them fairly quickly.

The problem with these gauges, when installed between the primary and secondary is you don't know if the secondary is getting clogged. You should actually install it after the secondary. Then again, if you keep up with your primary changing the secondary shouldn't need changing. (Much)

You will see a buildup of vacuum when the filters get clogged. The vacuum goes away when you shut off the engine. They do sell the gauges with a 'set needle' that stays at the maximum, but this only works if you remember to re set it each time. Better to have a gauge to read when running the engine. You have to get all the air out of the line when installing. air is compressable. and alters readings.

Having a gauge on each filter is great. You get an idea which tank has the bad fuel. My boat has a common vac gauge after the primarys so I cant tell which tank is bad, so I have to change both.

I have seen as much as 7 lbs vacuum on mine when I had bad fuel. But the engine starts making telltale hiccup noises and slight rpm fluctuations. But I know it's coming, with confirmation from the gauge
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Old 11-19-2015, 07:00 PM   #9
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Have "the" gauge. But why worry unless there isn't sufficient fuel flow for full power?
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Old 11-19-2015, 07:04 PM   #10
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Have "the" gauge. But why worry unless there isn't sufficient fuel flow for full power?
I'd sort of like to know before I go through woods hole with 7 knots of current, rocks and ferrys to dodge if the fuel is got a high vacuum or not.

Totally predictive. Nothing like an extra thing to help me decide if/when filters need changing.

When I run on clean filters I show around 1 to 2 lbs vacuum. When it starts to clog up it moves slowly to 3 or 4 lbs vac. Time to change 'em before it's an issue.
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Old 11-19-2015, 07:18 PM   #11
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Is there an electronic "read it on the bridge" version?
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Old 11-19-2015, 07:24 PM   #12
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Fuel blockage doesn't happen all that quickly unless your engine(s) suddenly stall. Applying "full power" occasionally (every time out/daily when underway is a good test of fuel flow.
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Old 11-19-2015, 08:11 PM   #13
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Quote:
If you install a gauge don't get the ones that go on top of the racors. When you change filters the Tee handle gets dropped. Slippery fingers diesel and all end them fairly quickly.

The problem with these gauges, when installed between the primary and secondary is you don't know if the secondary is getting clogged. You should actually install it after the secondary.
Whaaaat?!!

1) I don't know what engines you are talking about, but you will find that the secondary is often, if not always on the pressure side of the fuel pump. So you need a pressure gauge over there if anything. I haven't seen otherwise, but then again I have far from seen them all.

2) The gauges replace the T-handle. In God knows how many filter changes, klutzy old me has had zero problems with this, and I am an expert at creating problems.

Quote:
I have seen as much as 7 lbs vacuum on mine when I had bad fuel
What kind of engine? 7 is very low and well into the green zone for every diesel I know of.
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Old 11-19-2015, 08:12 PM   #14
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Fuel blockage doesn't happen all that quickly unless your engine(s) suddenly stall.
Now gee, why would they do that??
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Old 11-19-2015, 08:23 PM   #15
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question: fuel filter vacuum gauge

Quote:
Originally Posted by caltexflanc View Post
Now gee, why would they do that??

You are correct. I have two secondaries. I forgot about the one just upstream from the fuel pump. For some reason the PO had another secondary after the primary's but before the lift pump. Perkins 4.236


When I was bringing her home last summer off Erie Pa the engine was making funny tonal hunting sounds. The vacuum was in the vicinity of 10 lbs. This summer after a rough trip it went to 7 and I changed them. Fuel filters are cheap. Wife and Grandkids aboard with engine problems.... Priceless. It's different with just myself as mechanic and Captain. Without an engineer I tend to err on the side of caution.

Wish I had a picture of my gauge. It is on a hose, which the PO ran up out of the engine room and fastened it along the edge of the companionway. Barely noticeable. But it is nice to be able to glance down to see how the Vac is holding. Or not. Without lifting hatches. Really, if you had to lift a hatch, would you? Or would you just keep running until it stopped? It would be like having Temp gauges under the deck. Pretty useless down there.
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Old 11-19-2015, 09:41 PM   #16
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Vacuum gages tell us when we are near ready to change the filters keeping us out of trouble and saving time and money. These are 2" gages glycerin filled with snubbers to quiet down the fuel pulses adding accuracy and make reading easier (about $20 each). A new filter is at about 2 psi and it will begin to flutter the engine at about 12 psi - it takes about 600 gallons burned per engine before the gage will go from 2 to about 8-9 psi.


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Old 11-19-2015, 10:48 PM   #17
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Fuel blockage doesn't happen all that quickly unless your engine(s) suddenly stall.
Engine(s) are there to keep the captain cool. Watch how un-cool he gets when they suddenly stop running.

Yes, been there done that. Fortunately there wasn't a thing to hit within 100 miles and the Ocean was flat, so I got it all sorted..... at 3am.
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Old 11-19-2015, 10:51 PM   #18
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[QUOTE=smitty477;389441]it takes about 600 gallons burned per engine before the gage will go from 2 to about 8-9 psi.

That all depends on whether you got nice, clean, fresh fuel last time you hit the fuel dock, how long it sat, what the wonderful world of biochemistry is doing in your tanks, and whether the sea state you're in is enough to shake something loose that grew a looooong time ago.

I've had it happen in hours.
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Old 11-20-2015, 06:59 AM   #19
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"That all depends on whether you got nice, clean, fresh fuel last time you hit the fuel dock, how long it sat, what the wonderful world of biochemistry is doing in your tanks, and whether the sea state you're in is enough to shake something loose that grew a looooong time ago."


Yes - of course it does I agree completely. It also has a lot to do with exactly which fuel filters you are running.
In a past boat I also have had filters plug within hours from new leading me to add vac gages to that boat as well - and on that boat I added two sets of gages on each engine one after a new bulk filter that I added and another after the Racors that were already installed. Those increased the time between filter changes by more than 400% until I could get the tanks much cleaner.
I find that the gages not only help with when to change the filters but also immediately rule out some potential engine problems when they are encountered.
I just mentioned the current real data point about 600 gallons since it always seemed better to change a filter when it needed it rather then based upon some other non related reasons such as seasonal or hours of use.
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Old 11-20-2015, 07:02 AM   #20
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I have Racor mounted gages on both filters. They work fine. I usually see 0 on the large 30 micron unit, and 1-2 on the smaller 10 micron unit with new elements.
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