O C Diver
Guru
- Joined
- Dec 16, 2010
- Messages
- 12,878
- Location
- USA
- Vessel Name
- Slow Hand
- Vessel Make
- Cherubini Independence 45
Few days ago there was some discussion regarding the yellow and red colored portions of the Racor Vacuum gauge for their fuel separators in this thread:
Fuel Filter Reduce WOT?
I wanted to follow up on this and post a little additional information in it's own thread after talking to my Cummins dealer, as I believe many members who have these gauges may not have seen this information before.
The Racor Vacuum Gauge shows vacuum in "Hg (inches of Mercury) from 0 to 30. From 0 to 7 the background is white suggesting the normal operating range. From 7 to 10 the background is yellow suggesting a caution zone. From 10 to 30 the background is red suggesting a warning zone. Through out the life of the filter element it may be normal to see some vacuum. On my trawler when the fuel tank is near empty, it's normal to see about 2"Hg of vacuum on the scale which reflects the effort to lift the the fuel from a lower level up to the level of the fuel pump. Also, it's common to see the vacuum level increase near the end of the filter element's life reflecting the suction required to pull the fuel through the dirty element. Finally, one can also see some vacuum if the engine has a high flow lift pump and the separator is not of an optimal size for that pump.
The point of the thread is to make people aware that the implied warning and danger zones are not reflective of the engine but possibly the separator housing or the element. The issue regarding your engine is the maximum vacuum that can be tolerated by the lift pump. Lift pumps vary by both engine manufacturer and engine model. When excessive vacuum is reached, flow may be reduced, stop, or even damage / break the lift pump. Manufacturers give maximum values for "Hg of vacuum in their engine data sheets. As an example: for the Cummins "C" series engines, the clean filter maximum vacuum is 2.5"Hg (normal operating conditions), and the dirty filter maximum vacuum is 4"Hg (end of filter element life). These are far below the Caution Zone (7 to 10"Hg) of the Racor vacuum gauge. According to my Cummins dealer, operating above the 4"Hg limit can and has caused terminal failure of these pumps.
I'm not suggesting that the particular engine you have in your boat has this same vacuum limit or that your lift pump will even terminally fail if you exceed the limit. What I want people to understand is that warning zones on the Racor gauge likely aren't your engine's limit and that you should consult your manufacture's engine manual to determine the true limits.
As an interesting comparison, the limits for my John Deere 4045 are 9"Hg in clean fuel and 12"Hg in dirty fuel.
Ted
Fuel Filter Reduce WOT?
I wanted to follow up on this and post a little additional information in it's own thread after talking to my Cummins dealer, as I believe many members who have these gauges may not have seen this information before.
The Racor Vacuum Gauge shows vacuum in "Hg (inches of Mercury) from 0 to 30. From 0 to 7 the background is white suggesting the normal operating range. From 7 to 10 the background is yellow suggesting a caution zone. From 10 to 30 the background is red suggesting a warning zone. Through out the life of the filter element it may be normal to see some vacuum. On my trawler when the fuel tank is near empty, it's normal to see about 2"Hg of vacuum on the scale which reflects the effort to lift the the fuel from a lower level up to the level of the fuel pump. Also, it's common to see the vacuum level increase near the end of the filter element's life reflecting the suction required to pull the fuel through the dirty element. Finally, one can also see some vacuum if the engine has a high flow lift pump and the separator is not of an optimal size for that pump.
The point of the thread is to make people aware that the implied warning and danger zones are not reflective of the engine but possibly the separator housing or the element. The issue regarding your engine is the maximum vacuum that can be tolerated by the lift pump. Lift pumps vary by both engine manufacturer and engine model. When excessive vacuum is reached, flow may be reduced, stop, or even damage / break the lift pump. Manufacturers give maximum values for "Hg of vacuum in their engine data sheets. As an example: for the Cummins "C" series engines, the clean filter maximum vacuum is 2.5"Hg (normal operating conditions), and the dirty filter maximum vacuum is 4"Hg (end of filter element life). These are far below the Caution Zone (7 to 10"Hg) of the Racor vacuum gauge. According to my Cummins dealer, operating above the 4"Hg limit can and has caused terminal failure of these pumps.
I'm not suggesting that the particular engine you have in your boat has this same vacuum limit or that your lift pump will even terminally fail if you exceed the limit. What I want people to understand is that warning zones on the Racor gauge likely aren't your engine's limit and that you should consult your manufacture's engine manual to determine the true limits.
As an interesting comparison, the limits for my John Deere 4045 are 9"Hg in clean fuel and 12"Hg in dirty fuel.
Ted
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