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Racor System Upgrade

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The "Prime" function of  my Racor filtration system is not working, so Racor has suggested I replace it with their "upgrade", the 790R30 system since the one I have is obsolete.  They tell me that "the fuel connections are not the same" but have not told me much more about the old system (pictures attached).  I had sent same pictures to them but they cannot/did not tell me the old part# or its specs so I'm not sure what to adapt from.  I know the 790R30 ports are  (SAE J1926) 7/8"-14 UNF from the spec they sent me.

The pictures attached show right angle fittings of a sort, they look like they're fuel line disconnects, but I'm not sure of that.  Ideally what I'd like to do is adapt from whatever these are to the 7/8"-14UNF threads in the 790R30.  Does anyone have a system with connectors like this?   Anyone adapted from this setup like mine to the 790R30?




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Not directly pertaining to your questions about fittings, but an increasingly popular fuel system modification is to bypass (or simply disable) the Cummins lift pump and install a FASS or Bully Dog  pump/filter system in the location of the existing primary filter.  The greatest value of this mod is to those of us with older CAPS injection pumps (1999 - 2004) used on ISC and ISL engines.  The CAPS pumps have a history of failures that are frequently due to fuel starvation and/or air ingestion.  The CAPS pump has its own gear-type internal fuel supply pump and its spec is to tolerate negative 5PSI on the delivery line from the filters.  This makes it susceptible to air infiltration and fuel starvation.  Providing positive pressure to the fuel inlet of the CAPS pump precludes that.

The FASS pump runs continuously, pumps at a rate in excess of 85 gallons per minute and returns excess fuel to the tank through a dedicated return hose, so it is continuously filtering and recirculating the fuel.  And, of course, it provides PRIMING capability so that if you chose to, you could install the filters dry.  The Titanium series includes two filters fastened to its body.  The primary one is for air separation, with the air, if any, being returned to the tank.  If the FASS pump fails, the internal supply pump of the CAPS pump will still draw fuel through the FASS system.  FASS is an acronym for Fuel-Air Separation System.  FASS system is approximately $700 and is a thoughtfully engineered, high quality system entirely made in USA.  You might consider it as an alternative to the Racor.  I installed a Racor system on my previous1993 Dynasty.

I installed this FASS Titanium system on my 1999 vintage ISC-350 (2000 Dynasty) along with a fuel pressure gage that reads fuel pressure at the CAPS pump inlet, and an EGT gage.  My installation was in anticipation of adding an Ag Solutions "chip" to modestly increase power.  The EGT gage alerted me to the fact that I needed to reduce EGT before adding any additional fuel.   I modified my wastegate to raise boost from 24 PSI to 30 PSI.  (Boost Fooler would have done the same thing for $15 and half-hour work.) That dropped EGT well over 100*F from a max of 1340*F under "torturing" conditions.  Under modest load (10-12 PSI boost) and steady 62 MPH, the EGT is less than 1100*F.  I have several thousand miles on the modifications, am satisfied with EGT reduction and will install the Ag Solutions "chip" shortly.


NAYSAYERS, CURMUDGEONS, AND PAP'S (Pontificating Apocalypse Predictors) -- Please remain seated with your lips sealed and hands off the keyboard.  I'm not suggesting you do ANYTHING I have done, but if you have the technical knowledge and mechanical expertise you will be pleased with the result.  I don't post things I've read on the Internet.  I post about things I have personal experience with.

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Personally I am not a big fan of the Racor system. Go to any freightliner dealer and look at the fuel filters. They are usually Davco. Fass is another popular system. Air in the fiel system is a real problem. I think Racor also has a more modern system.

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The system you have is the one described in my 2005 Exec Owner’s Manual, but mine came from the factory with a slightly different system installed. It had a “Prime” function but no drain. Something shorted out on our first long trip, and we had a constant “Water In Fuel” alarm. Took it to a shop in Portland, Maine, and they were stumped. got Monaco tech support on the phone (this was back in 2006) and their expert actually conferenced in their Racor contact. Upshot was that they recommended swapping to the 790R30. Had it overnighted in and they swapped it out easily; I don’t recall much of an issue with thread sizes. My current setup looks very similar to your picture in terms of the fittings and the yellow fuel lines. 

Years later, I added a 1/4 turn ball valve shutoff to the incoming line to prevent draining the line back to the tank while changing the filter, and I’m pretty sure I used standard pipe thread hardware from Ace/Star Hardware. This would have been about 10 years ago, so memory is fading.

I would recommend you actually get the new hardware in hand and then work through the connections, as speculation might lead to more confusion...

George C, 2005 Exec

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I added the Racor 790R30 to our 2005 Signature. I was able to the prime function to replace the fuel filters dry.

I also added some shut off valves either side of the filter.






Edited by pwhittle
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I finally received some info  from Racor about the older, obsolete system and I submit this to show similarities and differences (hoping this helps someone else):

  • Electrical wiring between coach and  filtration system are the same three:  12vDC power,  remote warning light, and ground; connectors may be the same. 
  • Part#s of the obsolete systems are 12962 for control and  48027 for the  filtration unit.  The new is 790R30.   
  • The fuel connectors are 7/8"-14 UNF fittings (SAE J1926) in both cases. 
  • If I can re-use my existing connectors  there may be space to put shutoffs in horizontally (I like  pwhittle' s idea of putting in shutoff valves). 
  • If the old connectors are not re-useable I'm not sure what's involved installing (crimping?) new ones.   Suggestions?
  • The filter elements used are different, the old using the Racor S3230P; the  new uses the Racor R90P.  
  • The now obsolete 12962/48027 system has prime and  "drain water" capabilities, whereas the new, 790R30 system has only the priming capability, with draining done manually.  

One possibility, now that I have the complete spec of the old system, is that problem diagnosis/repair may be possible.  If it's the momentary switch which is preventing the pump from working I may try that repair, at least in the short term.  If the pump motor is bad, I guess the whole thing is 'toast'.  One way or the other, I know I'll eventually install the  790R30 .

I am not sure  if I can post the documents Racor sent me.  All have copyright notices.



Edited by rpasetto
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Note:  From Racor's wiring diagram I was able to determine continuity of wiring to pump motor and of momentary switch.  Measured voltage from switch when momentary was pressed at <12vDC so that momentary switch button seems to need replacement. Cleaned contacts of 6 pin connector between control panel and pump unit with contact cleaner & put back together.  Pump worked.   Replacing the filter unit with the new 790R30 is now in the  *Eventually* section of my to-do list.

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  • 10 months later...

Thanks to all for your help and suggestions. I now have a plan (half the battle) to:

1. Check the existing system out thoroughly and if inoperable,

2. Replace the Priming Pump Assembly with the Racor 790R30 and the integrated Control Panel

3. Install Isolation Valves on the gzin and gzout (good idea)

Thanks again all, much appreciated


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  • 2 weeks later...

Hey morning everyone, I read your stories and I just wanted to give my 2cents worth.

I had installed the FASS system, for reasons that are similar to many others, however being a retired Mechanic I know priming the filters is huge, so rather than turn on the key and run to the filter bay to open and bleed them I chose to open there harness that was supplied with the FASS pump and include a Priming switch then I made a bracket and installed it next to the filters. 1,2,3, it has made normal maintenance sooooo much easier.

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While waiting for my790R30 to replace the old Primary filter Setup I came across a picture in the 06 Sig Manual, below.

image.png.6a837fcb0f91bc78004d89d4080d15b4.png       image.png.a86085a172caf06674579c8d10e059c0.png

The connectors on these look just like the ones on mine, and the filter system in the picture looks like the 790R30. It looks like it will be an easy swap if nothing breaks.  My concern is if those plastic connectors break, where to get a replacement, and how to install them on the hose ends.  Rather than that I would prefer the field installable metal type (JIC) but still not sure what size/type of that connector to get.

I wrote to Voss so hopefully answers will be forthcoming.


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On 4/19/2021 at 10:55 AM, Rob M cKeown said:

I have not started on installing the Racor 79030R yet but will advise on size of fittings when I do in the next few days

Do you have the rubber hoses with brass or steel threaded fittings on yours?... or the plastic VOSS connectors like mine? 

I just noticed that one of my fittings has a broken red clip. See Below,  I do not know what, if anything, the clip does to hold the fitting together.


I wrapped the tabs with a zip tie but do not know if that is sufficient to hold it.  

Has anyone with this type of connection replaced the whole thing with steel or brass "field-installable" fittings?


Edited by rpasetto
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