Racor fuel vacuum guages - SailNet Community
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post #1 of 10 Old 11-01-2019 Thread Starter
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Racor fuel vacuum guages

I am wondering what you advise regarding the value of Racor fuel vacuum guages to assess how clogged the primary fuel filter is. I think that the guages sense the pressure or vacuum between the primary fuel filter and the secondary filter on the engine. One recent Racor guage model has a second needle that records the most vacuum encountered since reset, so I could read it as part of my routine prelaunch engine check. My Crealock 34 has an electric fuel pump in addition to the pump on the engine, so there would be vacuum at the guage only when the primary filter is significantly clogged. Still, I am considering adding one so that I get some warning. (New owner, four year old fuel tank that hasn't been cleaned, at least two year old fuel, biocides added)
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post #2 of 10 Old 11-01-2019
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Re: Racor fuel vacuum guages

The first thing I'd do is insure the fuel and tank are clean, but adding a vac gauge is never a bad idea.


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post #3 of 10 Old 11-01-2019
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Re: Racor fuel vacuum guages

Here's a method to assay the correct 'when to change out the damn filters'.

Install a vac between the engine lift pump and the last filter in series. You can add other vac gages between each filter for greater control/observation.
All filters newly installed
Run fully warmed engine with trans in forward and boat securely tied to dock.
Run engine at WOT- wide open throttle ... as you slowly close the tank valve ... until the engine begins to 'stumble'
Record the vacuum reading at 'stumble'. Multiply that number by .85 (leaves you 15% of reserve in case Murphy comes calling.)
Periodically 'test' the engine and the vac gage at WOT ... if the vacuum is approaching that .85 value ... its time to change filters.

If you want to get fancy, install an electric vac switch (12vdc wired to an alarm) between the lift pump and the vac gage. with its set point adjusted to set off an alarm at the .85 value.
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Re: Racor fuel vacuum guages

If one will be buying fuel from reliable sources (virtually all US supplies would be and local knowledge should keep you away from the bad ones), a water separating primary and engine secondary filter is probably all one needs. The alarms and gauges are never a bad idea, but not really necessary for a weekend warrior in the first world. I think the OP is in FL, but not sure of the boat's intended use.

Be sure the tank and lines begin clean, keep water out and properly dose all fuel with a biocide. Then inspect the clear bowl on the racor and change the filters regularly. If the filter starts to become excessively contaminated, you'll know something is up long in advance.

If your fuel source is questionable, that's a different story. If it is, I'd also want a by-pass filter, so I could keep the motor running, while it get somewhere to make the repair.
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Re: Racor fuel vacuum guages

I would not want a Racor filter without a suction gauge. Without the gauge, you only have the equivalent of a dummy light...and that being, the engine dying of fuel starvation. Seeing that gauge needle move and hold steady in a counter clockwise direction is a very good indication of what is happening inside of the filter so it can be dealt with before the starvation happens.
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post #6 of 10 Old 11-02-2019
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Re: Racor fuel vacuum guages

Quote:
Originally Posted by Minnewaska View Post
If one will be buying fuel from reliable sources (virtually all US supplies would be and local knowledge should keep you away from the bad ones), a water separating primary and engine secondary filter is probably all one needs. The alarms and gauges are never a bad idea, but not really necessary for a weekend warrior in the first world. I think the OP is in FL, but not sure of the boat's intended use.

Be sure the tank and lines begin clean, keep water out and properly dose all fuel with a biocide. Then inspect the clear bowl on the racor and change the filters regularly. If the filter starts to become excessively contaminated, you'll know something is up long in advance.

If your fuel source is questionable, that's a different story. If it is, I'd also want a by-pass filter, so I could keep the motor running, while it get somewhere to make the repair.
Its not the fuel that goes into the tanks of reputable fuel suppliers. Its those fuel suppliers tanks.
The best ones filter from tank to pump, at the pump, whether in states or other...
Some truckstops filter but i dont see that for most land based furl suppliers...gas stations

Last edited by RegisteredUser; 11-02-2019 at 08:19 PM.
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post #7 of 10 Old 11-03-2019
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Re: Racor fuel vacuum guages

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Originally Posted by RegisteredUser View Post
Its not the fuel that goes into the tanks of reputable fuel suppliers. Its those fuel suppliers tanks.
The best ones filter from tank to pump, at the pump, whether in states or other...
Some truckstops filter but i dont see that for most land based furl suppliers...gas stations

Actually, its the fuel dealers with a high turnover of fuel, wherein the fuel is constantly diluted with 'fresh' uncontaminated and water free fuel, are the 'reliable' sources. This would be sources that are pumping 90% of their storage capacity per month. This would exclude almost all marinia where the fuel sits around for months before being pumped; only those marinas that service commercial or mega yachts should be considered reliable sources.

The reason for all this is that diesel fuel has a relatively short 'shelf life' when exposed to atmosphere ... drawing down of fuel from field tanks accelerates the aspiration of fungals (cladosporiiums) into the field tank vent. Moisture quickly equilibrates into the fuel through the field tank vent and open boat tank inlets when fueling and then through the boats tank vent. Most particles in diesel fuel are simply the agglomeration (growth of particles by electronic surface attraction into larger and larger particles).

Unless diesel fuel is hermetically sealed in containers, once open to the atmosphere the shelf life is only about 45-90 days before the contamnation starts to really accelerate to grow/agglomerate into a contamination bearing possibility.

Rx: buy your fuel only from high turnover sources*, do not 'top off' your tank but only take onboard what you will USE in a nominaly short time ... plus some reserve, Empty the tank for long term storage.
When buying fuel, FIRST step should be a test for contamination: pour some of the fuel into a clear glass container, then hold that glass ... full of oil up to strong light .. the glass between your eyeball and the light source and denote any 'haze' in the fuel. If haze, then the resident particles are already at 5M or greater ..... and you should close down and look for a 'reliable' source with 'fresh' fuel.

*buy your fuel at a high turn-over truck stop and 'jug-it' in to your boat.
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post #8 of 10 Old 11-03-2019
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Re: Racor fuel vacuum guages

I too have PSC 34, and I have a Racor vacuum gauge after the Racor 500 filter and before the Walbro electric fuel pump. I also have a 3 way valve between the Walbro fuel pump and the Yanmar fuel pump. That valve can direct the once filtered fuel back to the tank via a tee in the fuel return hose from the injectors, or the valve can send the fuel on to the Yanmar fuel pump and hence to the Yanmar fuel filter, high pressure fuel pump, and the injectors. In the half closed position the 3 way valve can block any flow beyond the Walbro fuel pump.

The three way valve allows me to purge the air from the Racor filter and fill the filter after I have changed the filter element or to "polish" the fuel in the fuel tank by running the Walbro pump with the engine off and circulating the fuel from the tank, through the Racor filter and Walbro pump then back to the tank.

The vacuum gauge serves two important purposes. First, I use it to prove that there are no air leaks into fuel supply system in the parts that are under vacuum. That is done by circulating the fuel from the tank and back to the tank for a few minutes, then closing the fuel supply valve at the tank, waiting until the vacuum gauge reaches a maximum, putting the 3 way valve in its closed position, shutting off the Walbro fuel pump, and waiting for an hour or two for the vacuum in the blocked off parts of the system to break off. With no air leaks the gauge will fall a little as some fuel vaporizes and remain stable after that. Second, I use the gauge to determine if the Racor fuel filter element is dirty. As suggested above I partially closed off the fuel supply valve at the tank to determine the maximum tolerable vacuum and applied a bit of a safety factor to the number. I put a mark on the gauge at that point and keep an eye on it.

Bill Murdoch
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Last edited by wsmurdoch; 11-03-2019 at 09:55 PM.
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post #9 of 10 Old 11-04-2019
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Re: Racor fuel vacuum guages

I like the alternate fuel polishing idea. However, the normal fuel pickup is above the bottom of the tank, so it would not likely ingest much of the settled contaminants. I think this is why it's positioned there and often only grabs sediment, when the tank is sloshed at sea. Do you find you do?

If I'm right, a couple more bits, for an alternate pickup, might do the trick.


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post #10 of 10 Old 11-04-2019
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Re: Racor fuel vacuum guages

The fuel tank on a PSC34 slopes both fore and aft and port and starboard toward the fuel pickup tube. The tube is in the lowest part of the tank and virtually touches the bottom of the tank. (The FWD arrow on the attached drawing is incorrectly reversed.) I have never had a fuel feed or filter plugging problem with sludge in the tank. However, this year in George Town, Exuma I bought 15 gal of fuel from the Shell service station that was contaminated with water and rust. I put one 5 gallon jug in the tank before I saw that I had a problem. The other two I settled overnight and decanted the good fuel into my tank. I then 'polished' the tank for six or eight hours collecting some rusty water in the Racor bowl before draining the bowl and replacing the filter element. Other than that I've little interesting to report.

I want my fuel pickup to pick up the crud in the tank so that the filter can get it out of the system. I don't want it to remain in the tank, accumulate, and bite me later.

The story is in the June 4, 2019 entry in my wife's blog. https://irish-eyes-to-the-bahamas.blogspot.com/

Bill Murdoch
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PS34 440037-PSC 34 FT STANDARD DIESEL (NO REV) 05-14-18-page-001.jpg  

Last edited by wsmurdoch; 11-04-2019 at 10:06 AM.
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