Fuel filter

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Well-known member
Nov 15, 2007
Mamers, NC
I can find only 1 fuel filter on my 330 Cat.  It is at the rear of the coach and serves as a water separator as well. 
Is there one somewhere else?  I located the oil filter and that is all.  Thanks
There were about 2 years where Freightliner only installed 1 fuel filter.  You may only have the one.
I have only one on mine Ron and I've took both floor panels in the bedroom up looking for another filter. I did find a sticker on the top of the motor that told me that it was a Cat 3126.
Happy trails  :)
2003-2004 and early 2005's typically had only one filter, per a relaxed requirement from both Cat and Cummins. Then they both went back to requiring both a primary and a secondary.
I built a primary filter with a manual priming pump out of spare parts.  Readily available on ebay..  Cat 112-6521 fuel filter housing and a caterpillar hand primer.

The hardest part is making up the fuel hoses to plumb the fuel from the tank to the new filter.  downstream from the new (primary filter) is the water separator/filter unit.

Let me be the first to remark that in most marine applications...which is where my expertise comes from...  We would have a Water separator/coarse filter (30-10 Micron) as the first line of defense and a secondary filter of a finer micron rating (2) as the last filter your fuel sees before it hits the injector pump.

My operation here will have a 10 micron primary filter and THEN go on to the 2 micron Water separator....

This is simply because I do not want to retrofit what freightliner set up.  If they figured that the one filter was sufficient....then my added primary filter should not be a problem.  The beauty is that I now have the ability to swap filters and manually prime the system.

That said....  Freightliner COUNTED on the remaining fuel in the line to be able to run that Cat 3126 until it filled the filter.  Their instructions explain NOT to prefill your filters.  Under perfect conditions, this might be ok.  E.G.  I am sitting here with a replacement filter ready to go on and I dont dick around with the system open too long.  BUt when I have to go inside and wipe the diesel out of my eye, or find where I dropped my glasses and I leave the system open too long.... Bad JuJu and we have an airbound cat.
Both Freightliner & Spartan used single filer fuel systems for a couple years in 2003-2004, with approval from Cummins & Cat. Apparently experience showed that two filters provided  more reliable operation, and Cummins withdrew their approval around the end of 2004 or early 2005. Chassis built after that time have two filters.

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