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Old 12-20-2020, 02:23 AM   #1
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CAPS, FASS and AirDog

Hi All, I'm up to my eyeballs on the CAPS fuel issues and many people adding pumps to their RV's. There is an active thread currently on a guy broken down in Denver with a fuel issue. It is this thread that has me and many others searching for more information etc. I have a question. Are there a lot of people who have absolutely no issues at all with their CAPS system and have high miles on their coach without every having added a pump or changed out their CAPS pump? I have no issue at all with my coach currently and have a factory 2 filter system that I am very religious about changing the filters on. I try and run from a full tank to a half, then fill up again. I change the engine oil at 8-10K miles. I am an old car mechanic from the 80-90s and am not afraid of working on my coach. I don't however want to (just yet) do anything to my fuel system as I have actually no issues and it runs great. Are there others out there like me? Also, has anyone found a different alternative to installing a FASS or AirDog? Maybe something out of the box so to speak? Just asking. Thank you.
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Old 12-20-2020, 10:17 AM   #2
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My '99 8.3 CAPS has 111,000 miles on it. I don't have the history before I owned it. I installed an Airdog as a preventive measure as I have many friends in the performance diesel world (pulling tractors) and the benefits IMO far outweigh just the Caps issue. Anyway, When I was installing the pump, I saw that my Caps pump was a rebuilt dated 2011. So, my 20 year old 100,000+++ mile coach has had at least one replacement. For what it's worth.
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Old 12-20-2020, 11:07 AM   #3
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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.
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Old 12-20-2020, 11:33 AM   #4
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I think Larry just answered your question as well as anyone could.
One other thing to consider...any fuel starvation, cavitation or fuel foaming can potentially destroy a CAPS pump. Why is this becoming more problematic now than ever? I believe one, these systems are aging. Not much can be done about that except good maintenance.
Two, I think this is the elephant in the room so to speak, the CAPS injection systems were never designed to operate on no sulphur diesel fuel. That lack of lubericity, coupled with occasional fuel starvation due to partially restricted filters under negative pressure is a killer over time.
I don't see how a good positive pressure fuel delivery system with a regular filter maintenance and fuel lubericity additive can hurt.
If anyone running a FASS or AirDog has lost a CAPS pump I'd sure like to hear about it....just my $.02c
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Old 12-21-2020, 09:41 AM   #5
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I have a Cummins 8.3 /315 hp ISC with about 70K miles in my 2001 American Tradition. While passing through Buffalo NY I lost all power coming through a toll booth. Towed to a Cummins factory shop where the diagnosis was a failed CAP pump assembly. With parts and labor the bill was about $5,200 and we lost 4 days of our trip. The new (factory rebuilt) was warranted for 1 year or 100K miles (100K on a motor coach, why bother.) It been 2 years now and Iíve put about 3K miles on it. The Cummins mechanic said he thought it was the original 2001 pump. The sudden interruption in our trip, the inconvenience of moving into a hotel, and the expense has me looking into of of the systems described here too. My biggest issue right now is finding a knowledgeable diesel mechanic who has installed these before.
Does anyone have a ballpark cost installed?
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Old 12-21-2020, 03:13 PM   #6
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Following with interest as well, I have had the stop engine light flash briefly and lost power on 1 trip. A change of fuel filters let me continue on, however I'm not sure fuel pressure is not playing into it as well.
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Old 12-21-2020, 03:21 PM   #7
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Old 12-21-2020, 03:38 PM   #8
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Make sure the bolts holding the priming pump (lift pump) are tight.

The leak at that gasket can leat air into the system, and that's bad.

A system like the FASS will eliminate that by supplying positive pressure to the CAPS pump. Also, it returns fuel to the tank, and suposedly air as well.
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Old 12-21-2020, 03:53 PM   #9
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CAPS, FASS and AirDog

I will tell you that it is hit or miss when it comes to the CAPS failures. Maybe I was lucky, I donít know. I owned a 02 newmar Dutch star with a 350 ISC. Bought it with 140k on the clock. Previous Maint. Records showed the accumulator was the only thing changed In the life of the injection pump. It had a 177K on the clock when I sold it. It only had the the FS1022 that I changed every 3k miles/ 6 months just so I didnít have any problems. That motor never skipped a beat. I now own a 400 ISL with caps. This will be my last coach unless I hit the lotto. Air dog will be added as Iíve already had to replace the lift pump. This coach has 110K on the clock.
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Old 12-21-2020, 04:15 PM   #10
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Does using a lubricity additive greatly reduce the chances of a caps failure?

Anyone know if using a fuel additive affect an Aquahot in anyway?
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Old 12-21-2020, 06:24 PM   #11
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Quote:
Originally Posted by irishguy View Post
Does using a lubricity additive greatly reduce the chances of a caps failure?

Anyone know if using a fuel additive affect an Aquahot in anyway?
I don't know, but they really do not like getting air inside with those super close tolerances. Just takes seconds to seize up with no fuel.

Probably won't bother anything, just might carbon up the DPF a little quicker, causing more frequent regens.

As far as the Aquahot, they will drink up anything close to diesel.
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Old 12-22-2020, 12:14 AM   #12
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Quote:
Originally Posted by irishguy View Post
Does using a lubricity additive greatly reduce the chances of a caps failure?

Anyone know if using a fuel additive affect an Aquahot in anyway?
Iíve been using Opti-lube for about 4 1/2 years with my Fass pump. Has not affected my Hurricane heater.

https://opti-lube.com/opti-lube-xl-x...1-280-gallons/

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Old 12-22-2020, 11:22 AM   #13
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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/
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Old 12-22-2020, 07:54 PM   #14
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I'm wondering if I can install it before my stock primary filter, instead of removing and replacing.

https://airdogliftpumps.com/product/...versal-150gph/
Instead of removing and replacing what?

I would install it after the primary filter and before the secondary. In other words, bypass the lift pump with two new hoses from the filters. Cap off the lines from the lift pump and if needed, can be used as a backup. Many members here are installing the expensive fuel pumps with two filters that constantly filters the fuel and returning it to the tank. Itís nice to have but not necessary. Iíve been happy with my Fass (pump only) for over 4 years.

https://www.lmperformance.com/783399...-d08-095g.html

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