CAPS, FASS and AirDog

[lbw6303]

This is a summary of a thread that I started in late 2019 entitled (Cummins ISC 8.3 Stalls and heals overnight. Fuel pump? ECM? )
The summary below tries to describe my conclusion as to the “Root cause” --- I concluded it was air getting into our fuel supply system and causing our diesel engines to stall --- In short --- I think it’s the low pressure CONNECTORS on the supply lines from fuel tank to lift pump – Total 4 of them. Air gets in – causes the fuel to become foam – thereby causing the pump to run under-lubricated until an internal pressure sensor shuts the engine down. No codes are set – the engine just suddenly shuts down. Won’t restart. Overnight, the air settles out of the foamy fuel – The engine starts right up and runs for many (100 – 200 miles until it happens again. GGGGRRRR!!!! Since installing the FASS, I’ve made two uneventful 2000 mile trips (total 4000) and the rig ran just fine.
A brief recap of my situation – 2004 Monaco Diplomat with 8.3 ISC Cummins/Allison drive train. This thread started because of 3 stalls That I had on a recent trip wherein the engine stalled unexpectedly and then seemed to heal itself over night (see post #1). As I got into trouble shooting mode, I believed that I had a earlier vintage “CAPS” pump system. Two months at Cummins in Tampa determined that mine is a “HPCR” (Hi Pressure Common Rail) system and thus a different lift pump and a “CAPS 2” injector pump that is fed by a Gear pump at 90 -130 PSI. The ECM actually controls the ignition sequence. The Coach manufacturer relocated the Cummins-designed secondary filter configuration from the passenger side of the engine to a driver side compartment for accessibility. My fuel flow is from the tank, through a 10 micron primary filter, through a lift pump, and then up to a gear pump. That pump feeds my relocated secondary, 2 micron.. filter at 110PSI. The output of that filter then connects to the input of the CAPS 2, HPCR pump for much greater pressurization and timely injection.
The Cummins baseline design for mine and earlier engine/fuel injection systems is to utilize a “lift pump” at “key-on” that runs for approx. 15-20 seconds to prime the injection pump and from there the Injection pump takes over and literally sucks fuel (at low vacuum) for about 20-30 feet from the fuel tank --- through the filters and the “resting” lift pump --- all day long!! This “terrible” design is IMHO the source of many of the pump failures and stall issues that so many of us have experienced. From my tank to the lift pump, are 4 low-pressure (vacuum) connections. These are like “quick disconnects” and I believe are quite susceptible to loosening with age, because of deteriorating seals, thus allowing air to be sucked through them ---- any one of these will, over time, allow air to be pulled into the fuel flow. The failure mode is that this air mixing with fuel eventually becomes like “foam”, resulting in a drop in pressure out of the gear pump to the injector pump making it increasingly difficult for the injector pump to create the pressures it needs for efficient ignition. When the supply pressure drops to around 70 PSI, a pressure sensor in the HPCR simply causes the ECM to shut the Injection pump down---no codes are set, no warning given, just dies as if you’d shut off the key!!!
It simply will not start right back up, even though the lift pump is activated, by the ignition key. The clues for me were two-fold; 1) inspection of the primary filter after the 2nd stall (because we always suspect we just bought contaminated fuel) showed that it was half empty/full of air as though I’d just run out of fuel; 2) by the 3rd stall I’d become suspicious of a magical healing process, because by just sitting for a few hours, like overnight, the unit would crank right up and run smoothly. My assertion is that the “foam” becomes real fuel again after a few hours because the air settles out of it and it can be properly pressurized again.
Others have found that their lift pump bolts were improperly tightened and that simply tightening those bolts was sufficient to stop the intrusion of air into the fuel flow. But IMHO, the underlying issue is not where or how, air gets in, it’s the fact that somehow it DOES and will with this “Sucking system”!! My Monaco spent two months at Cummins in Tampa. They ran exhaustive tests with very sophisticated equipment on both my electrical AND fuel systems. They found NOTHING!! I even offered for them to think outside the box and use their professional judgement to pick the two most likely parts they would replace if they were to just ”throw parts at it”!! No one would bite, Finally I got a rationale that went something like this ---- Usually in these intermittent kinds of situations, we ultimately find that some sort of “restriction” is causing the vacuum pressure to increase as the injection pump sucks the fuel, thus causing air to be introduced at places like the low pressure connectors. (translation by me --- This fuel sucking system sucks, but we’re also not fans of the FASS types of systems like you’re considering that puts the fuel supply system under a slight pressure either) ??????
The term “flapper” was used, I guessed that the term referred to a separation of the inner wall lining of the fuel line. All kinds of reasons came up in the forum traffic suggesting that the ULSD mandate for bio diesel causes fuel lines and connector seals and gaskets to deteriorate. Other horror stories included a shop rag getting into the tank, causing the pickup screen to be plugged/restricted. Algae clumps was another possibility. For an HPCR system, even a stuck injector could cause the entire rail pressure to fall below threshold and cause a sudden stall. But IMHO, it all boiled down to ----Air gets sucked in – the pump is starved for fuel – it might even heat up – it must surely be under-lubricated – the amount of air is so great that the fuel turns to foam – adequate pressure cannot be produced – the ECM intervenes to save the pump – STALL!!!! Solution??? STOP the AIR from getting in. The most likely places are two fuel lines --- 1) The feed from the tank to the primary filter (two low pressure connections), 2) the feed from the secondary filter to the input of the lift pump ( two more low pressure connections).
So here’s what I finally did. --- I had a FASS (titanium model) system installed. I’ve just driven 2,000 miles since that install was completed and am happy to report that all went very well. I replaced the fuel supply line from the tank to the input of the FASS pump. That eliminated 2 of the four low-pressure connections. I also replaced the fuel line that goes from the output of the FASS to feed the lift pump thus eliminating the 3rd & 4th low-pressure connections. This also meant that the original primary filter was replaced by the two built-in FASS filters. Pretty hard for air to get in now at all. The FASS still sucks fuel for about 20 ft or so, but the low-pressure connections are ALL gone and there is something in the design of the FASS that’s supposed to remove air also. I have a gage in my dash that shows the FASS pump output pressure (18.5 PSI +- .5 PSI) If the pump ever fails, I’ll know it right away. None of the other OEM plumbing changed. The lift pump operates the same. The ECM doesn’t know the difference. If the FASS pump fails, I will switch it off and a single ball valve will put my configuration back to “native/OEM configuration (Sans the low pressure connections that were the most likely root cause in the first place) --- the objective being to be able to “limp” out of the way of traffic rather than be towed.
The only tweak I will make yet is to include the original primary filter in this configuration, because currently (for expediency) when I bypass the FASS, I have no primary filter --- I want to get it back if I ever have to bypass FASS.
The only other tweak will be to include the Gear pump output gage, in the cabin, on the dash. I still have a gage in the filter compartment, but want to be able to monitor that pressure (110 PSI) as I go down the road. Just having that gage, would likely have forecast that I was about to stall last fall. This fix has been tested over a 2000 mile trip. My fuel mileage appears to be better and the engine ran great. In retrospect, my installer doesn’t believe that fuel lines were the problem and I probably could have left them alone. IMHO, it’s the four low pressure connectors that were/are the fatal flaw in the OEM design. Never-the-less, I would still install a FASS system, With these two gages, in the cabin, if I were making a recommendation to anyone. I also think that being able to return to “native mode” with a FASS bypass is a good fail-safe approach.
Beyond that, I now use Stanadyne lubricity and fuel treatment additives faithfully. The FASS is purportedly operating at a rate that has it cycling excess fuel back through the tank at a much higher rate than the OEM design resulting in a much better “scrubbing” of fuel to better remove contaminants.
Sorry this is so long, but this forum has been a huge help in getting this situation resolved even as the Cummins techs scratched their heads. I felt I owed you a wrap up post. If you don’t want to plow thru all 100 posts, I’d suggest (#1, #74, #83 & #96.). Thanks to all of you who have helped me get to this “FIX”!!

[CntryCoachRV]

I have an 8.3 ISC 350 Hp in a 2000 Country Coach with slightly over 120,000 miles. My original CAPS pump was replaced in Tucson Arizona, at the Cummins dealer which subsequently closed, under warranty in the fall of 2000, I was having an exhaust smoke issue and they were changing parts trying to fix the smoke issue. There was no problem with starting and engine ran fine so I am of the opinion that the original CAPS pump was working as it should. Fast forward to around 2015 and my lift pump started leaking and I was lucky to be near Colton Truck Terminal as they changed out the lift pump for around $700 including the cost of new pump and labor. Not looking forward to the day the CAPS pump fails. I know that is very expensive.

[TR4]

lbw6303,
Great to hear you got it figured out. One question, does your CAPS2 use the same lift pump as the original CAPS injection pump or does it use the one that has the ECM cooling like the newer injection pumps?

Bill

[45Auto]

Fascinating thread to say the least!
I have an 04 5.9 HO ISB. I love this thing! I have had issues with gelled fuel likely from sitting longer than it should. Since then I religiously use Power Service Diesel Clean, White and silver bottle. In addition to that, I also use the Power Service Bio Kleen to prevent the microbial algae issues if any. For additional fuel lubrication I use Marvel Mystery oil and or Lucas injector cleaner, of which I stand by today! It works! The wife can tell when I’ve added the Lucas or Marvel to her tank, fuel mileage goes back up to when it was new.. because of issues with lift pumps on these Cummins, I didn’t wait for mine to fail so I pulled it out and installed a FASS 95 in 06. I added the low pressure light along with the adapter plate for the OEM LP so I could retain my fuel heater. On occasion, at startup, it cranks over then instantly dies, then I can restart. May be time to check the fuel lines. For the longest time, I thought it may be a glitch with the computer,But after reading this thread I may need to check those lines for aging.
I haven’t heard it in this thread anywhere, but FASS is byproduct of Air Dog, they were a father and son operation until sometime in early 2000 they had some kind of fall out and went separate ways and the son started FASS, the rest is history.

[RockyCliff]

I have known I would be doing either FASS or AirDog for some time now on my 2001 HR Endeavor ISC 330 and have decided on AirDog. I would like to thank those that have posted photo and installation details on this thread. To those who have mentioned "Lance's" support at AirDog and have actually purchased their products, can you advise the contract information and how you purchased, that is I see "authorized" dealers listed on the internet, are they the channel you go through or is there a "factory" purchase option. Thanks,
Cliff

[Mile Marker 42]

Originally Posted by RockyCliff

I have known I would be doing either FASS or AirDog for some time now on my 2001 HR Endeavor ISC 330 and have decided on AirDog. I would like to thank those that have posted photo and installation details on this thread. To those who have mentioned "Lance's" support at AirDog and have actually purchased their products, can you advise the contract information and how you purchased, that is I see "authorized" dealers listed on the internet, are they the channel you go through or is there a "factory" purchase option. Thanks,
Cliff

So I am also going to install an AirDog only pump. I did speak to Lance and although he recommends the whole system opposed to just a pump, he does admit that a pump only install is still a 1000% better option than the factory lift pump. He gave me the Raptor universal pump part number and I bought it on ebay here. You cannot find accessories such as brackets, wiring etc easily, but I finally spoke to someone at PureFlow Airdog who directed me to a PDF document with some of the parts I want. That document is here. Scroll down to page 7 for the actual list. I am buying 1 of the frame brackets (not the set) and the spacer and the wiring harness. I am mounting my pump in one of my fake storage bays where the fuel fillers are. There is plenty of room on either side and getting to the "feed" hose of my tank to connect to the pump will be easy. I will bypass my lift pump and install this relay. I like this relay because it has a built in mount for the fuse. I will mount a fuel pressure gauge off my secondary filter which I will unbolt from the side of the engine and mount it next to my primary filter mounted outside the frame rail. I ordered this fuel gauge which is a kit that includes the sensor and mounting bracket as I plan to cut a hole in my dash and mount it cleanly. They also sell a 40ft wiring harness that I bought for $20 which will make wiring very easy. I am going to run a 1/2 inch grey electrical plastic conduit pipe from the rear of my coach to the front tank area and run the wiring through that along with some other wiring. I will need a couple of hoses and a couple of caps for the lift pump and a couple of fittings for the pump. I'll get key on power for the relay from the back battery or inverter bay, and key on power for the pump from the front left electrical bay. For those of you wondering why I am not going to install their complete unit, is because I am cheap and would rather save that money for other things I will eventually have to buy for my motorhome. The more I can save on each project, the more projects I can do:-) It wasn't my idea to do any of this until I read the thread from Frank who had broken down in Denver last month. Hope this helps a few out there.

[mg2016]

I have a 2000 American Eagle on a 1999 Spartan chassis. I have been following this Thread and previous Threads about the lift pump failures. I have 98000 miles, original owner. I contacted Airdog and spoke with Lance. I had several questions about the installation and after our discussion I decided to purchase the system. I was able to purchase directly.



Not a mechanic but I do my own maintenance. Will update the Thread after I complete the install. Hope to start next week.

[tomgagne]

Originally Posted by RockyCliff

I have known I would be doing either FASS or AirDog for some time now on my 2001 HR Endeavor ISC 330 and have decided on AirDog. I would like to thank those that have posted photo and installation details on this thread. To those who have mentioned "Lance's" support at AirDog and have actually purchased their products, can you advise the contract information and how you purchased, that is I see "authorized" dealers listed on the internet, are they the channel you go through or is there a "factory" purchase option. Thanks,
Cliff

I’ll be installing the complete Airdog unit and I purchased it direct through Airdog with Lance’s guidance/assistance. It comes complete with everything you’ll need, just explain your intentions for the install to Airdog and a kit of connectors will be supplied.

I intend on replacing my primary filter which is located on the street side of my coach behind the AC condenser. The only unknown at this point is the connection from the lift pump to the secondary filter, which is specific to the install. I will be keeping my secondary filter which is currently wired with the water sensor. The Airdog does not come with a gauge, but it does have a sensor for a low pressure light.

I’m scheduled to receive the package on 1/4 and won’t be installing it until the spring when the cover comes off the coach.

As I noted previously the assistance from airdog has been exceptional, and I expect they’ll be available if I do run into any issues during the install. Good luck to all!

[mackwrench]

Just thinking out loud but if you're installing a raptor pump VS a complete system.... what about leaving the OEM lift pump as is, and plumbing the raptor pump after the lift pump and before the secondary fuel filter?

The lift pump would not be under pressure when the airdog raptor is running.

There's no aux fuel return with the raptor, it's only job is the supply fuel under low pressure to the fuel pump.

I know the lift pump gasket can be a issue on older units... but many (me included) have replaced the OEM pump....the newer pumps should be biofuel / low sulfur compatible.

...not trying to start a peeing contest, just wondering why one would bypass a working system.

[Ljwt330]

Originally Posted by mackwrench

Just thinking out loud but if you're installing a raptor pump VS a complete system.... what about leaving the OEM lift pump as is, and plumbing the raptor pump after the lift pump and before the secondary fuel filter?

The lift pump would not be under pressure when the airdog raptor is running.

There's no aux fuel return with the raptor, it's only job is the supply fuel under low pressure to the fuel pump.

I know the lift pump gasket can be a issue on older units... but many (me included) have replaced the OEM pump....the newer pumps should be biofuel / low sulfur compatible.

...not trying to start a peeing contest, just wondering why one would bypass a working system.

I cannot answer for the person you are addressing, but others have asked the same question and, in general, the answer has to do with removing all possible obstructions or restrictions in the fuel flow to the main pump. Many have installed a positive pressure pump just as you suggest, and have had no issues. I would think it's a "peace of mind" as well as a "do it once and forget it" decision.

[Mile Marker 42]

Originally Posted by Ljwt330

I cannot answer for the person you are addressing, but others have asked the same question and, in general, the answer has to do with removing all possible obstructions or restrictions in the fuel flow to the main pump. Many have installed a positive pressure pump just as you suggest, and have had no issues. I would think it's a "peace of mind" as well as a "do it once and forget it" decision.

MackWrench, pretty much what Larry said. Replacing the gasket on my lift pump is a real difficult job and one I don't want to be doing on the side of the road in winter. See Frank's thread "Dead on the road". I prefer to take the lift pump out of the equation and also want to push the fuel and not suck it to the engine. Just a preference thing.

[ArtJoyce]

So following all the posts on lift pumps. Got me doing some research. We have a ISB with about 36k miles. So either I'm going to install a new Carter pump or Fass. Carter is the manufacture of the OEM pump.

Talking to a Fass sales shop that builds performance engines for tractors (tractor pull) next town over. He said either way is good, but the fast is a little more quality. He is very happy with my filters. With the fass I would be looking at $300 for the pump an $200 for him to install it.

[journeyman]

I am considering installing the AirDog up in the LP tank bay (behind the pass side front wheel).

Considering this for easy access and also to reduce the length of the suction line.

Does anyone see a potential problem with this?

[Rob_M]

Originally Posted by journeyman

I am considering installing the AirDog up in the LP tank bay (behind the pass side front wheel).

Considering this for easy access and also to reduce the length of the suction line.

Does anyone see a potential problem with this?

That’s exactly what I’m looking at doing. I really don’t see a down side as you’re eliminating potentially sucking air or collapsing an old fuel line. I’m interested in others thoughts on this also. Pumps are more efficient pushing than pulling.