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Old 08-23-2019, 07:15 PM   #1
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Cummins ISC - Engine Starts But Then Quits & Why We Upgraded To FASS TS Pump!!!!

This thread hopefully will save you a lot of time, frustration and money fixing your "SUCKY" Cummins Lift Pump.

We will also share our story with you, and then explain why we decided to upgrade our fuel delivery system and install a FASS TS electric pump (with filters) to safe guard our CAPS fuel pump from failure.

You will be surprised at how easily we fixed our Cummins-ISC-350HP (CAPS) engine which would sometimes would start but would then quit 30 seconds later. All we had to do is tighten 3 lift pump manifold bolts!

NOTE: Our Cummins engine is a 2003 ISC. And previous lift pump gaskets have been known to be more problematic than ours. So if you have an older coach you may need to replace the lift pump gasket -- and you need to double check you got the right gasket for your engine and lift pump if it has been changed since delivery.

After you fix your leaking "SUCKY" vacuum fuel delivery problem, then we highly recommend you upgrade your CAPS engine to a FASS Fuel Delivery System ASAP.

Enjoy the attached read and safe driving to us all!

See .pdf attached for FASS installation instructions on a 2004 Itasca Horizon 40AD with 2 remote mounted fuel filters.

...Basically, you just remove the primary filter and install a FASS TS Pump. You then will have 3 filters (20u=>10u=>2u) and you will have to pump a fuel return line.

...FASS also makes an Adjustable pump (FA) without fuel filters, but as you will find out there are significant advantages to the TS pump and it does not cost that much more to install. (And you can install the FASS TS pump yourself if you are armed with the information we provide you!)
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File Type: pdf Mark's FASS Lift Pump Installation Guide, (IRV2) 8-1-19 (PDF).pdf (2.76 MB, 346 views)
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Old 08-26-2019, 03:13 PM   #2
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TR4/BigLar368: Thanks for drawing a pink-highlight to show the "preferred" method of installing a FASS Titanium pump with filters.

...and since you guys keep "hammering me" (ha-ha) on why I plumbed my FASS pump like did, I will summarize my reasons so other owners know they their installation choices will probably be limited based on "Winnebago-Apples" vs "Monaco-Oranges." I.e., different chassis types dictate the installation you choose.

Specifically, on my 2004 Itasca "Horizon" 40AD I do not have easy access to the top of my fuel tank like BigLar368 has on his 2004 Monaco.

In addition, I have an Independent Front Suspension (IFS) that took up all the room in front of my fuel tank... and BigLar'3 Monaco has a straight axle and therefore room in front of the tank.

And in my engine bay, the primary filter and secondary filter was installed with fuel lines that were routed back tot he lift pump manifold... and I did not want to go to the extra time and expense of re-routing fuel from the FASS pump to the #3 filter (which was previously the secondary filter).

So I asked alot of people why I could not just remove my primary filter and install the FASS Titanium (TS) pump and filters in that same spot and no one had real answer other than "try it and see."

So I am pleased to report: After 2,000 miles I had no fuel leaks or pressure concerns by letting fuel pass into and out of the lift pump manifold. The fuel pressure in now 17PSI at idle and will drop to 15PSI when the Manifold Pressure (MP) is over 20".

I also think I can conclude these things:

* My fuel lines are fine and not rotted out on the inside.
* I have no vacuum leaks on the suction side of the FASS #1 filter, because if I did I suppose I would hear the pump cavetating (making a loud sound) and/or my fuel pressures would drop below 15PSI under load. Note: FASS says not put smaller than 20-micron filter on the #1 side of the pump, which is the suction side.
* We think the TS pump with 2 filters and return fuel line may help to keep injection pump pressures between 15-18PSI at all times. This is because the TS pump self-regulates and will return unused fuel back to the tank. We think this TS design is better than the FA pump which does not have any additional filtration or return fuel line.
* The FA pump also puts out 95 GPH, but without a return fuel line, all that fuel has to go though the injection pump. We did NOT like this idea since that would increase the fuel return pressures and then all the unused fuel would have to go through the 1/2" OEM fuel line.

Note: Brazel's says they always install the FA pump between your two existing filters; and they say there never has been any issues. So apparently the 1/2" OEM, CAPS return fuel line can handle the additional fuel return after installing the FA pump, but we still think the TS pump with a dedicated fuel return line and 2 filters is a better way to go.

So if you are willing to splice-in a 2" fuel Return Manifold (RM-1001) and run 36-38' of 1/2" blue FASS return fuel ($150 with split tubing). Then we recommend the FASS TS pump over the FA pump. And you will find the Dodge Ram mounting kit will work perfectly if you have an Freightliner Evolution Chassis like we have, because all you have to do is drill 2 holes in the existing chassis support and your TS pump will be ready to go in only 30 minutes vs. the FA pump that does not include a kit.

And as mentioned before, we like our 20u => 10u => 2u filter setup!

Note: The TS "Signature Series" pump is a strong and very, very quit pump. You will love it and it fits perfectly in your engine bay on the left side of the engine.

To summarize: YES... it would be better to mount the FASS pump closer to the tank, but that was impossible in our coach. Yes... it would be better to run a fuel line directly from the FASS pump-out to the #3 filter-in, but we see no reason why you can't just let fuel flow back to the lift pump manifold and follow the diagram we provided.

* And if you only have 1 filter on your Cummins ISC then you should be able to take it out and install a FASS TS pump in it's place, so long as you have enough fuel line to work with. So if anyone, has this configuration, please let us know how you make out!

Side comments:

* No fuel snubber valve is needed. A) You can install a fuel pressure valve on top of your secondary filter block using a 10mm x 1.0 to a 1/8" npt... if you get a 1/8" fuel pressure gauge off Amazon. Or B) you can install a sensor in the FASS 1/8" npt fuel port and then run 4-wire (speaker wire with insulation) with your FASS return line so you can reach your front, dash firewall.

* The sooner you upgrade to a FASS TS or TA pump the better, because your CAPS injection pump may be running on borrowed time! Then disconnect the Cummins Lift Pump and add a high quality relay between pins 85 & 86 to the ECM leads to keep a check engine light from popping up on your dash.

* If you have Monaco your installation will be more like TR4 and BigLar have described.

* If you have a Winnebago product with a Freightliner Evolution Chassis, your FASS installation will be like ours if you have remote mounted fuel filters in your engine bay... and then you can get switched-ignition power from the pink wire in your 7-pin tow light wire harness.

* FASS does not have an RV kit at this time, but we hope they put one together soon! We think there are a number of RV owners who will want to do a FASS upgrade just as soon a s they find out what it is and how to do it themselves... or how to coach a diesel mechanic to do it for you!

Over and out!
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Old 08-26-2019, 03:28 PM   #3
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Winnebago-Itasca FASS TS Pump Installation Pictures

More pictures that show how I spliced in the fuel Return Manifold (RM-1001) which is silver in color; and how routed the fuel lines with 4-wire (Speaker Wire with insulation) to remote mount a fuel pressure gauge in my dash.

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Old 08-28-2019, 08:47 PM   #4
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Very impressive.

That looks like a job for me after I retire.
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Old 08-29-2019, 03:26 PM   #5
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Thank you. I had fun researching this subject and with help from TR4 and BigLar368 along the away I was able to figure my fuel delivery system out and how to best install a FASS TS Pump in my Itasca-Freightliner Chassis.

FASS Tech support and Parley's Diesel (FASS Distributor) also field my questions; and in the end the Dodge RAM Truck Kit for the 1998.5 to 2002.5 fitment (Titanium Kit #: TS D08 095G ) worked out great!

I also used almost all the Dodge Kit parts and that saved money. And while modifying the wire harness was easy, it still took a few hours.

So I wrote FASS asking them to build a FASS RV-TS Kit and to start educating their distributors on the RV market, because I think most RV owners with a Cummins ISC/ISL engine don't know much about the FASS pump upgrade -- but will want to buy the TS pump if they did.

If you want to read the email I sent to FASS, and to further clarify what parts you need to add to the Dodge Kit for your RV installation, please download the attached .pdf.
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Old 09-29-2019, 02:09 PM   #6
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Very happy with the fass fuel pump - every caps owner needs one!!!

I am very pleased to report that I just completed a 8,500 mile trip after having installed the FASS Titanium fuel pump and it performed flawlessly!

The roads were of all types: From Montana to Texas to Chicago to Old Quebec City in Canada to Brooklyn-NYC and back to Chicago...

...And my engine just kept running better and better for the first 3,000 miles! My guess is that the FASS extra fuel filters was cleaning all he crud out of my fuel tank and I never knew my engine could sound this good.

Engine benefits:

* Starts up faster

* Sounds smoother at idle and at higher RPM

* The CAPS injection pump now receives 15-18 PSI of positive fuel pressure which provides 95GPH of cooler fuel and better filtered fuel.

* No more vacuum problems that could potentially starve the CAPS pump of diesel fuel, which leads to premature pump failure.

Side benefits:

* The FASS pump returns unused fuel to the tank. This also means it is constantly filtering fuel over-and-over. They call it "fuel polishing."

* FASS stands for air separation and they claim your fuel injectors benefit from removing the air from your fuel. As a CAPS injection owner, this not that important to me, but you HPFR owners may find your engines purr after you install a FASS lift pump.

* I think my algae concerns are now a thing of the past!

* I now have 3 fuel filters and can now filter my fuel down to 2-microns without any concern of fuel restriction. (Note: Cummins stock fuel delivery systems warn about filtering below 10-microns to avoid fuel restriction.)

* I can use standard Fleetguard fuel filters and other brands since the FASS filter thread size is the same size.


I felt like the FASS upgrade was so beneficial that I decided to add "Power Chip" to my 2003-Cummins-ISC-350HP-CAPS engine and I am very glad I did.

I really like the extra 60HP and torque! That's about 18% over stock and you will like how your coach rides over hill-and-dale at 65MPH without downshifting!

I also like the 10-15% increase in highway fuel mileage too. However, I think when you are on mountain roads you will find you get less MPG, because you will stepping on the fuel peddle to much.

Previously I was getting between 7.0 to 7.4 MPG on the highway... doing 55-60MPH and towing a small Saturn Aura toad. (No wind and good surfaces.)

...But after I added the Power Systems "Agricultural Diesel Solutions - Truck Edition" Power Module #12100 I now get 8.1 to 8.5 MPG and I can easily do 65MPH - 70MPH when towing.

Note: There seems to be no penalty for "chipping" your engine by using this Ag-Diesel-Power-Chip; however, we cannot speak for other brands. We can tell you that if you start driving at 70MPH you will burn more engine oil... but you will still get better MPG!

The parent company is called Power System Innovation and they have been putting their chips in farm tractors for years. They have also built a solid reputation in their Indiana farm community; and they are just now introducing their products to the RV market.

The #12100 Power Module now has a lower price too. Only $710 on Amazon.
And the best part is that the installation is very, very easy. So easy, almost anyone can do it in 1-2 hours or less.

We now feel our Cummins-ISC-350HP is easily capable of putting out 410HP, and you will FEEL THE DIFFERENCE IMMEDIATELY!

Before you order, we recommend you call Power Systems Innovations at 812-618-9166 to verify the part number for your type of engine.

Last but not least: The #12100 Power Module does not have a selector switch (at this time) for you to pick your desired HP/torque increase. However, we when we installed our 12100 in our RV, we did so at the Power Systems Innovations shop in Newburgh, Indiana; and we put our RV on their Dyno; and what we found is that a total of 410HP is all you need for a 32,000 lb. coach (pulling a toad). Further, we do not recommend more HP than this, because it's unnecessary, but I suppose you can ask the techs to push-it to 425HP if you want.
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Old 09-29-2019, 02:35 PM   #7
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I really appreciate the detail you shared in this post. Do you know if your ISC 8.3L is the CM554 engine?

I'm trying to adapt your plan for my coach. I only have a single 10 micron filter + water separator per Spartan and the Cummins shop manual for my engine.

Was this your starting point too?
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Old 10-11-2019, 01:39 AM   #8
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Glad to be of service!

Yes... I have a 2004 Itasca "Horizon" (40' DP -32,000 lbs) with a 2003 Cummins-ISC-350HP-CM554 engine... Freightliner Evolution Custom Chassis.

The key to the way you will plan your FASS electric TS pump (with 2 filters) will mostly be based on your chassis manufacture:

A) If you have access to your fuel lines on top of your fuel tank. (Monaco have an inspection plate to give them access to the top of their fuel tanks. In this case you just add a "T-Fitting" to the tank so that both your CAPS return fuel line and your FASS return fuel line can share the port. Then you just cap-off the OEM fuel deliver line that goes to the stock lift pump, because you will by-pass the pump... and plug the FASS delivery fuel line to either your 3rd filter or you can go direct to your injection pump.)

Then all you have to do is add a relay to trick the ECM into thinking their is a load on the other end to switch on and off so you don't get a "check engine" light. (See .pdf in previous posts.)

Note: The above also assumes you do NOT have an Independent Front Suspension (IFS) and/or you have room up front to mount the FASS pump near the fuel tank.

B) If you have a Winnebago coach with a Freightliner Chassis then you do NOT have access to your fuel lines and you have to do the installation the why I diagrammed above.

In this case you need to find a way to mount the FASS pump in your engine bay, which turned out to the the easy part in my Freightliner chassis. Just look for a flat mounting bracket on the left side of the engine bay, and then use the Dodge brackets in the FASS kit. They will work perfectly and these brackets are 1/4 steel so they are very strong.

* Examine your fuel lines and be sure you have the right parts before you start.

* Cutting the fuel tank filler neck was not hard. Just us a saws-all and a good metal blade. Our filler neck was 2" which is the silver color filler neck you will need to order separate because the Dodge FASS Kit come with a blue 1-1/2" fuel manifold with "Y" fitting for the return fuel. You also need to look at your slideout mechanisms to make sure you mount it out of the way.

There will be things you need to workout as you go, but overall it's not too hard. The first time you will want to be over cautious. Like how to run the fuel lines past your exhaust. We ran them almost horizontal from the tank to the engine on the driver's side, and the only concern we had was avoiding the Turbo exhaust pipe.

* We also have a side radiator on our coach so I'm not saying everyone has room in their engine bay for a FASS pump.

* For +12V you can go straight to your ENGINE battery bank.
* For switch +12V off your ignition key, we tapped into the 7-pin tow light connector for the +12V used to for power brakes... which we don't have since we pull a toad. BTW, at first this did not seem like a good idea, but with over 5,000 miles on our FASS pump I can now say that worked out great.

* We also ran 4-wires with the FASS fuel line and then hooked up a remote fuel gauge so we can see it when we drive. This is really nice to have, but I think you would do fine to buy an oil-filled fuel gauge, and a 10mm male to 1/8"NPT female adapter, that can mount on top of your 3rd filter... if you have a 10mm plug on to top? This will let you examine your fuel pressure from the engine bay when you do your pre-flight walk-around.


What chassis does your Newmar have? Spartan right? Do you have easy access you have to your fuel lines above your fuel tank the way Monaco owners do?

Do you have an IFS?

Do you have a side radiator?

Is your stock fuel filter in your engine bay or do you have a side bay dedicated for fuel filters?

Where are you planning to mount your FASS pump?


I think all Cummins engines will benefit from a FASS fuel pump; and I don't know why anyone would spend money to repair or replace their stock Cummins Lift Pump. Mind you, the stock pump is a good pump, but not the right pump for a Diesel Pusher applications.

* Be sure to download the .pdf in my previous posts so you can have a complete description on the installation I used -- and how I wired the relay to the ECM after I by-passed the stock Cummins Lift Pump.
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Old 10-11-2019, 02:13 AM   #9
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AG-Diesel "Truck Addition" Power Module (aka "Chip")

We were so please with the FASS upgrade we decided to take our Cummins-ISC-350HP coach to Power Innovative Solutions (Makers of the AG-Diesel #12100 Power Module) in Newburgh, Indiana ...and there we put our RV on their dyno.

All we can say is that we wish we "Chipped" our engine sooner!

On the dyno proved our Cummins-ISC went from 347HP stock HP to 420HP. That a true 20% increase in HP and torque we can feel. You will too! It's that obvious!

$709 On Amazon:

You will be amazed at the added acceleration in the 25-65 MHP range! And our MPG when up from 7.2 MPH to 8.1 MPH (towing a Saturn Aura 4-door sedan). Now the problem is keeping under 70MPH!!!

So don't ask for 30% more HP. In our opinion you don't need it and you will only be stressing your engine unnecessarily. On the other hand, it will not take you long to get use to the extra HP and you will want more! ...But don't do it. Stick with 20% more and then if you want you can always remove the huge muffler and put in a 5050XL muffler/resonator you can order on Amazon ($100 + clamps). We plan on doing this next year.

The Ag-Diesel Power Module upgrade is easy to install and you can do yourself in less than 2 hours. It's a very worthwhile upgrade in our opinion and if you drive a lot then you will be saving ~$20/full tank (assumes $3.00/gal). And if diesel fuel goes up then you will save even more... and reach your ROI faster! The point is that you will have fun stepping on the accelerator pedal and you will be able to merge onto freeways safer!

We say: "Buy the AG-Diesel for the extra ponies! ...And keep it for the extra MPG!"

Note: Our #12100 "Chip" did not come with a switch to select HP levels (+10% or +20% or +30%), but we have been told that future versions will have this feature. So if you are done RV for the season, you might want to wait for the next revision to come out.

* We also would not "Chip" a Cummins engine unless you add a FASS fuel pump first.
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Old 10-11-2019, 06:13 AM   #10
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Originally Posted by imnprsd View Post
Glad to be of service!
I appreciate the help. Thanks.


What chassis does your Newmar have? Spartan right? Do you have easy access you have to your fuel lines above your fuel tank the way Monaco owners do?
Spartan Mountain Master. I am not sure on access. I haven't been under that part of the chassis yet.

Do you have an IFS?
Yes. Reyco Granning IFS1200.

Do you have a side radiator?

Is your stock fuel filter in your engine bay or do you have a side bay dedicated for fuel filters?
It's on the opposite side of the coach as the radiator. It's under the battery compartment. I only have 1 filter. 10 micron with water separator.

Where are you planning to mount your FASS pump?
I have room in the rear side next to the filter. I hope to find room closer to the tank near the front. I do have fuel filler on each side of the coach.
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Old 10-21-2019, 07:57 AM   #11
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FASS tech support is great. Anytime you have a question, just give them a call and they will give you good advice... even though they are not that familiar with RV applications they know what their Titanium pump can and can not due.

Here's what they will likely say:

* Mount the FASS pump as close to the fuel tank as possible.
* Use the same diameter fuel return line as the fuel delivery line.

Note: The pump is a constant velocity pump and is has a spring inside the fuel return line. So the back pressure in the fuel return line is important to the pump putting out 15-18 PSI, but as one member told me: "Any positive fuel pressure to your injection pump is better than what you have right now."

Note: Fuel pressure does not always correlate to fuel flow. Meaning, you can't say for certain how much fuel flow is reaching your injection pump unless you pump a "flow meter" in line. And no one is going to do that, but you can trust the FASS design spec. And since the Titanium Pump you get is rated 95 GPH they tell me that's way more than you ISC will ever need... even under full throttle... accelerating or climbing grades.

* You can put additional filters after the FASS lift pump, but not before.

* You can substitute other fuel filters and put them in any order you want. Naturally, we are talking about larger microns followed by smaller micron filters. My filter setup is 20-micron on the FASS #1 side (this is the suction side); then 10-micron on the FASS #2 side (out); and my third filter is the FASS 2-micron filter that came with the FASS "Titanium" Kit.

* Don't go smaller than 20-microns on the FASS #1 suction-side. This to to make sure you do not restrict the fuel flow to the FASS pump... else the FASS pump may make noise.

* FASS came out with the 140-micron filter and made is "serviceable". That means you can clean it an re-use it. This maybe an advantage to a Dodge owner who drives a lot of miles, but I will just change out all my fuel filters every 2 years because of age, not use. (Note: FASS says to change filters every year, but I don't think this necessary if you use a biocide when you store your RV.)


* FASS uses a 140-micron filer on the suction side, because the kit is designed for Dodge-Cummins applications and their V44-Injection Pump has a very weak injection gear pump.

* FASS tech support is not that familiar with DP applications or the ISC-CAPS injection pump. So you might need to provide your own feedback. Just refer to the chart I provided and then modify it for your chassis needs.

Remember, the chart I drew is for my Winnebago with a Freightliner Chassis; but you Monaco owners with Spartan chassis can probably mount your FASS pump closer to the tank... but if you can't I would not worry too much about that.

As for Newmar owners with an IFS, I don't know if there is enough room up there? However, I think there is room to add the FASS pump to the filter bay? Hopefully, we will see pictures of these FASS installations in the near future.

My FASS "Titanium Pump" is mounted in my engine bay and it's been performing great for over 5,000 miles now.

I'm starting to see my fuel filter pressure drop to 14-PSI under acceleration, so I'm still monitoring the meaning of this. I first thought it might be fuel filters getting clogged, but I'm not sure. The only way for me to know is to change out one of my filters and then see if the FASS fuel pump pressure goes up 1-2 PSI. TBD. I will post these results next season.
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Old 10-26-2019, 02:42 PM   #12
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Hi Everyone. 1st post. anyone gave any guess on what install cost might be.
Thankd Craig
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Old 10-27-2019, 03:59 AM   #13
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Time to install

This is a good question.

It depends on your chassis and how your existing fuel deliver system is plumbed. And by that I mean it depends on if your your existing remote fuel filter lines are in good shape and are reusable.

It's like this: Once you tear apart your fuel delivery system, there is no moving your coach after that... unless your engine starts and keeps on running.

We decided to install the FASS "TS" pump with the fuel lines, and did NOT by-pass the lift pump in the beginning.

We took our RV to Freightliner-Spokane and all lthey did was hook-up the
dummy-relay to the ECM. (See picture.) And they did a good job, but it cost us $350 for a "Fricken" relay and adapter wire!

As a rule this is what I find true. Anytime you take your RV to the shop or do it yourself:

1) It always takes you more time than you think it should.

2) It always cost more than you think it should.

That said... for the average owner I would recommend they pre-install the FASS fuel pump without messing with the fuel lines or the ECM wires to the stock Cummins Lift Pump. And then if all is going well, you can install the "yoke" in your fuel line by the fuel tank.

I would recommend you go as far as you feel comfortable going, understanding that each application will be different from what we have documented -- unless you have the same model RV. In our case I showed pictures of a 2004 Itasca "Horizon" 40AD.

Then you can drive your RV to a qualified mechanic to finish the job.

...And by qualified I would recommend a diesel performance shop specialized in installing FASS fuel pump on a Dodge or Chevy. Or you need to find a Freightliner dealer or RV shop that has installed a FASS fuel pump before.

The Performance Diesel Shops are the most knowledgeable about installing a "FASS KIT," but you may find they do NOT know how your CAPS injection and ECM play together... so help them. They assume your CAPS pump is like a V44 pump and it is... but different when it comes to the gear driven pump... so help them understand your stock lift pump TURNS OFF after 30 seconds and does not run after that. They will accept this point if you tell them you have researched this matter fully.

Specifically, you need to install a dummy-relay to trick the ECM into thinking there is a pump (a ohm load) on the other end so you do not get a "check engine light."

As for time to install from scratch (,,,,assuming you provide the mechanic with all the necessary parts):

Beginner: 2 days
Intermediate: 1.2 days
Advanced: 8 hours

You can do the math based on shop rates; but if you pre-install the FASS fuel pump you will save money.

If possible, get a firm quotation up front.

Note: If you have a Freightliner Custom Chassis, you will be able to mount the FASS TS pump using the Kit Parts by drilling 2 holes. And the rest of your time will be spent "fishing" the return fuel line to the tank; and wiring the pump for power. A) Tapping in to the tow light gang plug; and B) Running additional 12-gauge wire to the engine battery.

If you have a Spartan Chassis you will probably be mounting the FASS TS pump very close to the fuel tank -- and luck you -- you should have access to the top of your fuel tank to install a "T-Fitting" so you can return fuel from the FASS pump to the tank; and then you will run a long fuel delivery line to your remote filter in your engine compartment... or you can plump it direct to your CAPS injection pump.

Good luck. You will be glad you did this upgrade. And next you will want to add an Ag-Diesel Solutions "Power Module." We did! ...And wish we did so 4 years ago! ... Then again, both the FASS TS pump and the Ag #12100 were just revised in 2019 and are truly ready for market bases on our experience (over 3,000 miles on the Chip and over 5,000 miles on the FASS "TS" Lift Pump.
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imnprsd is offline   Reply With Quote
Old 10-29-2019, 08:42 PM   #14
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Posts: 795
FASS TS PUMP INSTILLATION DIFFERENCES * Itasca-Freightliner vs Monaco-Spartan


Monaco RVs, and possibly others with a Spartan Chassis, may have access to the top of their fuel tank. And if you do, then you can remove the fuel supply line and hook it up to your FASS-IN-LINE. Likewise, you can remove the fuel return line fitting and add a "T-Fitting" ... so your tank can receive recycled FASS TS fuel and your OEM fuel returned from your lift pump.

Then your decision will shift to the best location to mount your FASS TS PUMP (with 2 filters):

A) You can choose to mount it near your fuel tank; or

B) Your engine bay or maybe you have a fuel filter bay.

Either location will work. FASS just doesn't want you adding any "check valves" or filters before the FASS TS PUMP, and they don't want you to run the fuel line higher than 3-feet above the fuel tank (bottom I assume). So don't be convinced you have to mount the TS pump near your fuel tank.

Other considerations include:

*Do I have room near my fuel tank to mount the TS pump with filters in this area?

...My guess is that you don't have room if you have an Independent Front Suspension (IFS). TBD

...And if I do mount the TS PUMP with 2-filters underneath your front end, do I have enough height to crawl under my RV with the jacks down? ...However, I suppose you can always drive a tire up on a curb to get the height you need. (Just a thought.)

Freightliner Chassis like I have on my 2004 Itasca "Horizon" 40AD do not have access to the top of the fuel tank; and since I DO have an IFS, there was no room by the tank. Consequently, I was forced to mount my TS pump in the engine bay, which turned out to be a great location!

...And fortunately, my Itasca-Freightliner has a side radiator.

...And fortunately, my Itasca-Freightliner was previous converted to a 2-filter system so I did not have deal with all the fuel lines that are routed back to the Lift Pump MANIFOLD.

Note: Please don't call the "LP-Manifold" a lift pump. It's not. It's a "manifold" that routes fuel like a highway cloverleaf (when trying to understand it.

The real lift pump sits underneath the LP-Manifold; and NO fuel flows through it after the ECM shuts it off, thanks to a check valve in the LP-Manifold.


I say I was fortunate to have a 2 filter setup only because someone else routed the fuel lines (properly) from the LP-Manifold to the new primary filter on the left side of my engine bay. (The 20u filer with a viewing bowl).

...And with the 2-filter upgrade, the mechanic turned the single OEM filter mounted on the right side into a secondary filter (10u).

...And again I say fortunate, because all I had to do was remove the primary filter on the left (looking at my engine) and I replaced it with the FASS TS pump. (Very easily because my existing fuel lines in the engine bay area were the right length!)

* The real fortunate part was that all I had to do was:

-- Drill 2 holes to mount the TS-Pump (Using the Dogde Ram Truck Kit)

-- And then turn one of my fuel line fittings 90-degrees to mate it with the FASS Filter #1 inlet. (Worked out great!)

* I suppose if your RV only has one filter in the engine bay (presumably on the right) you can mount the FASS-TS pump on the right side of your engine bay in the same manner, because the right side chassis frame also has a "FLAT" steel area -- and you can drill 2 holes in it just like I did. (See picture with yellow tape so you can draw the template. Just be sure you do NOT drill the hole too close to the frame or you will not be able to place a washer on the underside.)

FACT: In my Itasca-Freightliner application I ran 38' for the FASS TS fuel return line and connected to the "Y-filler neck" I installed in my fuel filler neck.


The real concern about the right way to install a FASS TS pump seems to be centered around:"What do I do about by-passing the Lift Pump Manifold?"

In my Itasca-Freightliner installation I did not by-pass the LP-Manifold and all is well. I now have driven ~9,000 miles since I installed the FASS TS Pump and my engine has never run better.

Would I want to by-pass the LP-Manifold? "YES!"

Would it be easy to by-pass the LP-Manifold in my Itasca? "NOT FOR ME."

In my case, I would have needed to tap into my fuel delivery line located at the LP-Manifold; and that effort was beyond my experience and abilities.

Plus I concluded that I might not have the right tools to compete the job; and should anything go wrong, then I would not be able to drive my RV to a shop. So I decided to work with the "hand I was dealt" and I decided to leave the LP-Manifold "AS-IS."

Why not? ...No one can tell me this is a wrong. Not even Cummins. And believe me I called Cummins several times and talked with their second-level support team. (All great BTW.)

Further, I found no one IRV2 who could state as a matter of FACT that it was wrong to leave the fuel lines "AS IS" and let the fuel run (under pressure) from the FASS TS Pump to the LP-Manifold.

What these members do say is that they would not recommend it; or "I would not do it that way." So I took a chance; and this is what I can share with you now:

...After my FASS TS PUMP installation and after ~9,000 miles of driving, I have NO PROBLEMS WHATSOEVER with the installation as I have documented it. (See .pdf Installation Guide in previous post.)


I think any average person with good mechanical skills can install a FASS TS Pump in any RV if you use the information I have provided and adapt it for your application.

I think Spartan Chassis owners have a choice when it comes to where they mount the FASS TS PUMP: In the front or in the engine bay, but Freightliner Chassis owners probably do not.

And factors like having an IFS and side radiator do come into play; in addition to existing fuel line condition, available length, etc.

Further, if you do route your fuel lines to bypass your stock LP-Manifold (and plug the unused ports) then you might consider letting a professional mechanic do this part of the job... or the whole job for that matter.

Regarding labor costs: I'm guessing a Truck Shop will want to charge you for 2 days of work or about $2,000 in labor. Further, they will not be challenged by hooking up the relay to the ECM, but they may not like cutting into your fuel filler neck. TBD

I also don't think you will NOT find an RV truck shop who has ever installed a FASS TS in an RV. So you might have better luck taking your coach to one of those Diesel Performance Shops who have installed lots of FASS and AirDog Pumps. (If they have room for your RV.)

These guys will have no qualms about cutting into your fuel filler neck, but you will have to school them on adding a relay to fool the ECM.

I also think a Performance Truck Shop will quote you 1 day of labor, but they may end up billing you for 1.5 days. I really don't know.

As a final note: I don't think any shop would mind if you if you pre-installed the FASS TS Pump; and then you can drive your RV to their shop to deal with disconnecting and reconnecting the fuel lines and wiring the electrical. In fact, I think you will find them curious about your FASS-RV-UPGRADE!

Good luck with our installation and please share how you decided to do it!

==> Be sure you print out the attached .pdf Installation Guide for more information and pictures.
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cummins, upgrade, engine

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