tcr1016
Leander, TX
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Joined: 02/21/2004
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Why do diesel pushers have 2 fuel filters. My 94 Cummins has 2 filters (1 bowl 30 Micron, 1 fuel 20 microns). I have changed the 20 micron down to a 5 micron. I am wondering if I still need 2 filters. What is the difference between the bowl and the regular filter?
1995 Safari Sahara 33' (5.9 230HP Cummins Diesel) Diesel Pusher
Daily Driver even to the store, Home Depot, restaurants, etc.
1 Dog (Great Dane/Greyhound Mix) goes everywhere with us.
My License Plate Frame Reads:
MY BIG
TEXAS SIZE SUV
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Dog Trainer
Richmond Mi.
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Joined: 08/17/2006
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My 93 5.9 230 Hp cummins has only one fuel filter. I guess it is the manufactures preference as to how many filters. I have never had any problem what so ever with the fuel in this coach.
93 Airstream 35' Dp
5.9 230 uprated to 300 HP
Allison MD 3060
Dutchess and Shadow (fur Bearing Children)
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Emmons
Alabama
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Joined: 04/26/2001
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Our bus has 2 fuel filters also.
After having to replace the fuel pump, I change both filters on a regular basis.
Better safe than sorry. 
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tcr1016
Leander, TX
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Joined: 02/21/2004
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Emmons wrote:Our bus has 2 fuel filters also.
After having to replace the fuel pump, I change both filters on a regular basis.
Better safe than sorry.
I would think that having 2 filters is harder on the fuel pump, since it has to pull through both.
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50pascals
rochester, ny
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Joined: 01/10/2008
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The jockey or booster pump pushes up to the filters then to the injection pump.
The first filter is a coarse one to remove large debris and water. The second one is a fine filter, and maybe a little more water there - though I've never found any in either.
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chuck4788
West of the Middle
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To clarify some of the previous posts:
There is a fuel pump on the engine, referred to as a "lift pump", that sucks fuel from the tank and pushes the fuel thru the engine mounted filter on its way to the injection system. The engine mounted filter is pressurized by the lift pump and the frame mounted filter is on the suction side of the pump. Any leaks on the suction side will let air into the system.
The engine manufacturer installs the filter on the engine to protect the injection system, the chassis builder will often install a filter on the chassis to assist the engine mounted filter by trapping water and large particles. This prefilter allows the engine filter to operate longer without fouling.
The good news is most automotive diesel fuel is pretty clean so we don't have many problems with bad fuel, plus a fouled filter is just an inconvenience on the road. On a boat a fouled filter can have more severe consequences so all boat diesels have water separator primary filters. All of my boats were setup with Racor primary filters in addition to the filters on the engines.
The best way to protect your fuel system is to buy from large volume dealers and have the tank full during storage, the reduced air space from a full tank helps reduce the amount of moisture that can enter the tank. Fuel bacteria need moisture, diesel, and warm temperatures to grow; so eliminating moisture is usually the easiest way to prevent the growth. Bacteria bodies can quickly foul filters and continued growth can become a maintenance PITA.
Chuck
02 Beaver
505hp C12 Cat
Trailblazer toad
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Hjudge49
St. Augustine, Fl.
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Having only the "second" fine micron filter will risk clogging much quicker. As previously stated, the primary filter removes large particles and water that would quickly clog the secondary filters. Fuel can never be "too clean". On my boat, I have dual primaries (separ and racor) for each engine, followed by dual secondaries with a bypass valve. You really, really don't want to be changing filters 50 miles offshore in 6-8 foot seas, in a hot engine room. BTW, that's always when stuff from the bottom of the tanks gets roiled up and enters the fuel lines.
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wolfe10
Texas
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Good answers, Chuck and Hjudge49.
The primary fuel filter/water separator is between the tank and lift pump.
The secondary fuel filter is between lift pump and engine.
Splitting filtration duties between a course and fine filter MATERIALLY extends filter life.
I am shocked that Cummins would suggest a 20 micron final filter-- that will pull out the "rocks" but that is about all. Caterpillar REQUIRES a 2 micron element. I thought (do not know) that Cummins uses a 5.
Brett Wolfe
1993 Foretravel 36' U-240
Cat 3116, Allison 3060
Caterpillar RV Engine Owner's Club: www.catrvclub.org
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Norm Payne
Livingston, TX
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My Cummins / Spartan ISL engine has two filters. The primary is a 10 micron filter and water separator and the secondary filter is a 2 micron. I change both once a year and carry spares.
Norm
2005 Dutch Star 4015, Cummins ISL 370 hp
2007 Honda CR-V
See Ya Down The Road
http://www.seeya-downtheroad.com
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