CAPS, FASS and AirDog

[castlemusic]

Originally Posted by TR4

Instead of removing and replacing what?

Sorry, Bill, should've been more specific. From what I've seen, most folks remove their primary fuel/water separator and install the FASS Titanium or AirDog 4G pump and filter combo in that location. Like you said, nice, but expensive! If the main problem is fuel starvation that kills the CAPS pump, I'm wondering if the cheaper pump only, from FASS or AirDog, would do the trick to provide positive pressure, instead of the CAPS working on a vacuum. I see a lot of folks adding just the pump to their ISB motors, but not the ISC. I see you have an ISL - is that also a CAPS system?

[Meames1]

Originally Posted by castlemusic

Sorry, Bill, should've been more specific. From what I've seen, most folks remove their primary fuel/water separator and install the FASS Titanium or AirDog 4G pump and filter combo in that location. Like you said, nice, but expensive! If the main problem is fuel starvation that kills the CAPS pump, I'm wondering if the cheaper pump only, from FASS or AirDog, would do the trick to provide positive pressure, instead of the CAPS working on a vacuum. I see a lot of folks adding just the pump to their ISB motors, but not the ISC. I see you have an ISL - is that also a CAPS system?

Yes, installing a positive displacement pump will do just fine for supplying constant fuel to the CAPS pump. The additional features are just that. I agree with TR4 , just install it after the primary filter and bypass the factory lift pump.

[Ljwt330]

Originally Posted by Meames1

Yes, installing a positive displacement pump will do just fine for supplying constant fuel to the CAPS pump. The additional features are just that. I agree with TR4 , just install it after the primary filter and bypass the factory lift pump.

I always get confused by "primary" and "secondary" filters because my ISL has only one filter, the fuel/water separator, located after the lift pump.

If one installs a positive pressure pump anywhere after the lift pump, there is no need to by-pass it as the positive pump will still be drawing fuel through the lift pump under negative pressure. Issues arise when the positive pressure is before the lift pump and this is the situation where many choose to by-pass the fuel inlet/outlets due to erratic fuel pressures or eventual leaking at the lift pump.

[TR4]

Originally Posted by castlemusic

Sorry, Bill, should've been more specific. From what I've seen, most folks remove their primary fuel/water separator and install the FASS Titanium or AirDog 4G pump and filter combo in that location. Like you said, nice, but expensive! If the main problem is fuel starvation that kills the CAPS pump, I'm wondering if the cheaper pump only, from FASS or AirDog, would do the trick to provide positive pressure, instead of the CAPS working on a vacuum. I see a lot of folks adding just the pump to their ISB motors, but not the ISC. I see you have an ISL - is that also a CAPS system?

Yes, it’s a CAPS. Here is a picture of my pump using the stock filters and bypassing the lift pump. The old lift pump fuel lines are capped off in the filter bay and can be reconnected in fifteen minutes as a backup. I also installed a fuel pressure gauge to monitor the filters. This pump will also allow fuel to be pulled through it by the CAPS gear pump if it fails. This will allow you to continue driving to a repair facility.

This is a good thread to read regarding the CAPS pump;
https://www.irv2.com/forums/f123/rep...lp-289659.html

[TR4]

Originally Posted by Ljwt330

I always get confused by "primary" and "secondary" filters because my ISL has only one filter, the fuel/water separator, located after the lift pump.

If one installs a positive pressure pump anywhere after the lift pump, there is no need to by-pass it as the positive pump will still be drawing fuel through the lift pump under negative pressure. Issues arise when the positive pressure is before the lift pump and this is the situation where many choose to by-pass the fuel inlet/outlets due to erratic fuel pressures or eventual leaking at the lift pump.

Sorry I wasn’t clear. I would not recommend running fuel through the existing lift pump. First, it’s a restriction. Second it’s prone to leaking. If it’s under pressure, it will leak fuel. If it’s on the suction side and leaks, it will allow air ingestion causing fuel starvation.

Bill

[Ljwt330]

Originally Posted by TR4

Sorry I wasn’t clear. I would not recommend running fuel through the existing lift pump. First, it’s a restriction. Second it’s prone to leaking. If it’s under pressure, it will leak fuel. If it’s on the suction side and leaks, it will allow air ingestion causing fuel starvation.

Bill

I agree completely with your assessment. Many have not bypassed the lift pump for the reasons I mentioned, but it still is the weak link for all the same reasons. Ease of installation is the main reason.

Keep in mind, both Airdog and FASS are marketed as pumps that remove air from the fuel supply. If they can handle the air from a leaking lift pump is another matter, however.

[Arkansas RV]

Originally Posted by Ljwt330

I don't think I qualify as high mileage but I've not had any issue with my CAPS system. However, the previous owner had the lift pump replaced, due to a leak, just prior to my purchase, and we all know that is the first link in the chain of failure.

My answer to your question would be, yes there are people out there with high mileage CAPS pumps that have had no issue with the main CAPS pump, but have had to deal with a failing/failed lift pump or lift pump gasket. They are two different pumps and points of failure and your question is only about the very expensive main CAPS injection pump.

Your maintenance procedures are excellent for maintaining the system, and you likely will have little issue unless/until the lift pump leaks, and you cannot prevent that without replacing the gasket with a new one that resists the effects of modern diesel fuel, so keep monitoring the lift pump for signs of fuel leakage or symptoms of air in the fuel system such as hard start, loss of power under load, or hesitations.

No "out of the box" remedies to address the weakness of the system because the weakness is in the original design of drawing fuel to the main pump under negative pressure over long distance. Strains the main pump and allows for cavitation or other sources of air to enter, undetected, which endangers the cooling and lubrication of the main pump.

Though I haven't installed a positive pressure system yet, I plan to as a preventative. Your choice, as well. Obviously you take good care of your system and it has worked perfectly for many years and miles. Still, the lift pump will eventually fail in some manner. If you catch it early, no problem. If not, it becomes a very expensive repair.

I concur with your explanation completely. My 2000 DSDP with 88K miles had no problems. However I wanted to be pro active to avoid costly expenses and break downs. The 8.3 ISC and ISLS are bullet proof. The weak link in the system is the lift pump which only runs for 30 seconds at startup. My research showed me that many leading diesel shops recommend doing this conversion for the obvious reasons.

[Arkansas RV]

Originally Posted by castlemusic

I too have been following this thread and others like it with interest. My '99 ISC has a rebuilt CAPS pump on it - sticker on the side says 2017, so a previous owner must've gone through similar issues and costs.

Wanting to prevent a future failure, I'm researching as well. Leaning towards the AirDog for simplicity, but the cost of the pump is holding me back. Has anyone installed an AirDog Raptor pump on an ISC? Significantly cheaper (by about half) of the 4G model, and I'm wondering if I can install it before my stock primary filter, instead of removing and replacing.

https://airdogliftpumps.com/product/...versal-150gph/

I would highly recommend you use the
AirDog FPll-150 or 200 Iniversal 4G pumps as these are for the larger Diesel engines in the trucking industry or motor homes

[Flanz]

Reading and following this thread since I’ve had a pump issue recently and have NO knowledge of diesel motor fuel systems, but I’m learning!!

Our coach, see signature, has a Cummins ISL9 450hp motor, 2017. About 3 or 4 months ago I lost the injector fuel pump. Had a loss of power while trying to enter onto the Highway on a slight grade when all hell broke loose. Fortunately, I was able to back down the on ramp and return to the campground.

Once back at the campground and settled into our site I turned the coach off. She wouldn’t start again after that. Called Cummins and was told to replace both the primary and secondary fuel filters. Replaced - no start. Since we were in a pull in site tow was NOT an option. Cummins sent a mobile technician to us and diagnosed and replaced the injector pump, holy crap the bill was outrageous, thank god we were still under warranty!!

So, my question is, are there bad/problem injector pumps? Could this have been caused by starvation of fuel or an air block? Coach has over 40K on the clock and I’m RELIGIOUS about maintaining the coach... i.e fuel filters, oil, air filters and ALL periodic maintenance. Once the injector pump was replaced the coach cranked over without a problem....

Just wanted to throw my experience out there and get thoughts from this thread.

[Mile Marker 42]

Originally Posted by Flanz

Reading and following this thread since I’ve had a pump issue recently and have NO knowledge of diesel motor fuel systems, but I’m learning!!

Our coach, see signature, has a Cummins ISL9 450hp motor, 2017. About 3 or 4 months ago I lost the injector fuel pump. Had a loss of power while trying to enter onto the Highway on a slight grade when all hell broke loose. Fortunately, I was able to back down the on ramp and return to the campground.

Once back at the campground and settled into our site I turned the coach off. She wouldn’t start again after that. Called Cummins and was told to replace both the primary and secondary fuel filters. Replaced - no start. Since we were in a pull in site tow was NOT an option. Cummins sent a mobile technician to us and diagnosed and replaced the injector pump, holy crap the bill was outrageous, thank god we were still under warranty!!

So, my question is, are there bad/problem injector pumps? Could this have been caused by starvation of fuel or an air block? Coach has over 40K on the clock and I’m RELIGIOUS about maintaining the coach... i.e fuel filters, oil, air filters and ALL periodic maintenance. Once the injector pump was replaced the coach cranked over without a problem....

Just wanted to throw my experience out there and get thoughts from this thread.

I am curious, are you the original owner? When your coach acted up and then wouldn't start, do you remember how much fuel you had in the tank? Had you been under the coach at an earlier time and maybe seen some leakage near the lift pump?

[Ljwt330]

Originally Posted by Flanz

Reading and following this thread since I’ve had a pump issue recently and have NO knowledge of diesel motor fuel systems, but I’m learning!!

Our coach, see signature, has a Cummins ISL9 450hp motor, 2017. About 3 or 4 months ago I lost the injector fuel pump. Had a loss of power while trying to enter onto the Highway on a slight grade when all hell broke loose. Fortunately, I was able to back down the on ramp and return to the campground.

Once back at the campground and settled into our site I turned the coach off. She wouldn’t start again after that. Called Cummins and was told to replace both the primary and secondary fuel filters. Replaced - no start. Since we were in a pull in site tow was NOT an option. Cummins sent a mobile technician to us and diagnosed and replaced the injector pump, holy crap the bill was outrageous, thank god we were still under warranty!!

So, my question is, are there bad/problem injector pumps? Could this have been caused by starvation of fuel or an air block? Coach has over 40K on the clock and I’m RELIGIOUS about maintaining the coach... i.e fuel filters, oil, air filters and ALL periodic maintenance. Once the injector pump was replaced the coach cranked over without a problem....

Just wanted to throw my experience out there and get thoughts from this thread.

Your coach has a different type injector pump than those in this discussion. You have the High Pressure Common Rail injection system, not the CAPS system. You also have a lift or transfer pump, but it is not subject to the same type of failure as the CAPS lift pump. I cannot speak to any issues with that system except to say it was developed, in part, to address the weakness of the CAPS.

Generally speaking, your main pump is subject to the same causes of failure, such as excessive air, lack of cooling, and poor lubrication. 40k miles seems like an unusually short distance for failure, but at least you were under warranty. Personally, I haven’t heard of many Common Rail main pump failures, nor of the lift pump which is located behind the ECM.

[Flanz]

Originally Posted by Mile Marker 42

I am curious, are you the original owner? When your coach acted up and then wouldn't start, do you remember how much fuel you had in the tank? Had you been under the coach at an earlier time and maybe seen some leakage near the lift pump?

Yup, we’re original owners. Tank was 3/4’s full and we had just sat for about 4 months. Prior to leaving I was under the coach and had just completed a lube of the chassis and no leaks.

I guess it was just bad luck on our part that this pump failed.

[Flanz]

Originally Posted by Ljwt330

Your coach has a different type injector pump than those in this discussion. You have the High Pressure Common Rail injection system, not the CAPS system. You also have a lift or transfer pump, but it is not subject to the same type of failure as the CAPS lift pump. I cannot speak to any issues with that system except to say it was developed, in part, to address the weakness of the CAPS.

Generally speaking, your main pump is subject to the same causes of failure, such as excessive air, lack of cooling, and poor lubrication. 40k miles seems like an unusually short distance for failure, but at least you were under warranty. Personally, I haven’t heard of many Common Rail main pump failures, nor of the lift pump which is located behind the ECM.

Thanks for the explanation Larry. No mechanic here, just enjoy doing my own maintenance. I’ve chatted quite a bit with the mechanics up at Spartan whenever we had work performed there. I have received may tips on how to do maintenance and what to look out for while doing it. Very helpful information which helped to cut down our maintenance cost.

I agree, 40K is unusual and the mobile tech who came out also said the same. He claimed that in all his 40yrs at Cummins that this may have been his 2nd or 3rd failed pump he installed. He had no explanation as to why it could have failed. I asked him about a lubricant for the pump and he mentioned Power Service products since they were recommended by Cummins. May start to use them, but a little bit of research is needed. And yes, good thing we were under warranty, cost for the pump and installation would have been ~7K......

[Ljwt330]

Originally Posted by Flanz

Thanks for the explanation Larry. No mechanic here, just enjoy doing my own maintenance. I’ve chatted quite a bit with the mechanics up at Spartan whenever we had work performed there. I have received may tips on how to do maintenance and what to look out for while doing it. Very helpful information which helped to cut down our maintenance cost.

I agree, 40K is unusual and the mobile tech who came out also said the same. He claimed that in all his 40yrs at Cummins that this may have been his 2nd or 3rd failed pump he installed. He had no explanation as to why it could have failed. I asked him about a lubricant for the pump and he mentioned Power Service products since they were recommended by Cummins. May start to use them, but a little bit of research is needed. And yes, good thing we were under warranty, cost for the pump and installation would have been ~7K......

Sounds like you're on top of things, which is always good.

Your injection system, especially since it is a 2017, was built to handle Ultra Low Sulfur diesel, unlike the CAPS system. ULSD caused shrinking of seals in the early systems, and the reduced lubricity put the pumps at a higher risk of failure. Your HPCR system was built for the new fuel and suffers many fewer consequences. That being said, adding lubricity products cannot do any harm, IMO, given the high pressures and close tolerances in the HPCR system.

Air in the fuel is still a killer, however, as it reduces both lubricity and cooling within the pump, not to mention performance.