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Topic: Cummins ISC CAPS intermittent stop engine light (long!) (Read 5545 times) previous topic - next topic

Cummins ISC CAPS intermittent stop engine light (long!)

Background: The first electronic Cummins 350HP ISC's were equipped with the CAPS (Cummins Accumulator Pump System) and started with the 99' model year on U270 and U295 Foretravel Unicoaches. Cummins went to common rail fuel injection on the ISC's and ISL's around 2003. The electronic lift pump on CAPS equipped Cummins ISC 8.3 only runs for 30 ~ 45 seconds after the ignition key is turned on to prime the system. That means the gear pump part of the CAPS fuel injection system has to suck the fuel through about 25' of fuel line to supply the injectors, as well as to return the unused fuel back to the tank after sending it through the fuel cooler. While this arrangement seems to work fine in a front engine vehicle like semi truck where the tanks are much closer to the engine mounted electronic lift pump, on a diesel pusher this set up sounds to me like a problem waiting to happen. I believe that our coach is on the cusp of such a problem. I have read about people paying six coach bucks to have Cummins put in a rebuilt CAPS pump. The cost of a rebuilt CAPS pump is about $3000 with a $1000 core charge.

The way the issue manifests is that when the load goes up (along with the boost) say while climbing, even in rolling hills, I will get a momentary stop engine light. I say momentary because as soon as I hear the ding I have been trained (like Pavlov's dogs) to instantly reduce throttle and or downshift until it stops, usually a second or two, though sometimes on cruise control the stop engine light comes on and lasts for about half a ding and goes off so quickly that I don't even have time to look down and see it. This typically occurs with 70% or more sustained load or intermittent higher loads as indicated on my VMSPC. The boost corresponds to the load of course, and I start anticipating the dreaded stop engine light whenever the boost is in the high teens for a sustained period, though briefly seeing up to 25 PSI while accelerating from a stop light doesn't usually cause the issue. VMSPC  shows the error code as 233, bad program. I have used the Cummins Insite software on my Panasonic Toughbook to check things out and the code thrown shows up there as an over pumping error. It amounts to fuel starvation.

One possible cause is an air leak between anywhere between the tank and the suction side of the CAPS gear pump could cause fuel starvation at the CAPS pump. I have checked all the fittings and everything else back by the engine and could find no sources for air leaks, though I guess I can't rule out a microscopic crack in a fitting or the metal fuel lines between the lift pump and the CAPS pump. I am not sure how to check for what amounts to a vacuum leak in a fuel line. without removing them and using pressure. Foretravel installed new fuel lines in 2014 and I suppose it is possible that there could be a loose fitting somewhere on the suction side of the equation. There is no evidence of a fuel leak. The problem could also be caused by a clogged primary or secondary fuel filter, but I have changed the engine mounted secondary filter twice if memory serves and I know there is no restriction in the primary. I changed the primary filter from the original Racor R90P to the Davco 382. It helped but hasn't completely solved the issue.

To address the issue, I am thinking that my next step is to install a fuel pressure gauge somewhere in the system before the CAPS pump, though the gauge will actually be showing a vacuum after the lift pump stops running and the CAPS pump is doing all the work. I would like to use an electronic gauge with a sender back by the CAPS pump and use a couple of the extra wires to feed a gauge in the dash. To make space in the dash, I will replace the two air pressure gauges with one dual air pressure gauge and put the fuel pressure gauge in the vacated spot. It is my thinking that this will confirm that it is the CAPS pump starving for fuel that is throwing the stop engine code.

The next step is to identify an appropriate pressure/vacuum gage and find the best place to install it. Two possibilities come to mind. For diagnostic purpose, a 'tattle tale' type gage that has an extra red needle that parks at the highest (or lowest) setting attained until cleared. these can be analog or digital. The preferred type of gage for me would be an electronic gage with a sender so I can monitor it from the dash. I have looked before, though not exhaustively, but I wasn't able to use the VMSPc to monitor fuel pressure or temperature though I know that the Cummins ISC has sensors for both since they can throw an error code.

The next step after gage(s) is to add a lift pump that runs continuously while the ignition is on and feeds the CAPS pump with a low positive pressure (5~7 psi) but with as high a volume as the CAPS fuel injection pump requires for cooling and supplying the injectors. At this point, I am considering a FASS UP95 lift pump commonly used in Dodge Cummins pickups that are tweaked for performance. It has adjustable fuel pressure with 95 gallons per hour. There are models of this pump that can support up to 260 GPH. There is one member on the FMCA forums with a cummins ISL CAPS Monaco Diplomat who has done this successfully. He was told by Cummins that you can't put a lift pump in front of the engine mounted electronic lift pump because there is some part in said pump that will reach critical mass and cause the sun to go super nova or some such... So his solution was to keep the OEM lift pump in place and bypass it. In order to fool the ECM into thinking that it was still there, he put in a relay on the lift pump harness that would put a load on it. The original lift pump includes a manifold that takes the return fuel and sends it back to the tank. In his case, he was able to locate the new FASS lift pump next to the tank, which is ideal and his set up has the fuel water separator and primary filter cartridges as part of the assembly.

That set up won't work in our set up, so I plan to locate the new pump after my Davco 382 primary filter. Though I know it will go between the Davco primary and the engine mounted secondary, I am not sure about exactly how I will go about that yet. It would be so much easier if I could simply put it in line before the existing pump. Since the Caps pump is sucking fuel through the OEM lift pump 30 or so seconds after the key on event, I fail to see why a 5 to 7 PSI positive pressure would damage it. Any way, I could simply bypass it and use a relay to turn on and LED light or something... Still just spit balling here, but I need to come to some firm decisions pretty quickly. I may eventually need a rebuilt CAPS pump one of these days anyway, but I am of the opinion that this fuel system tweak would be good insurance and perhaps delay that eventuality. Looking for input...

I plan to update this thread as things evolve because I feel the need to document this project in a way that help me remember, as well as add all the pertinent information to the coach documentation for a possible future owner.
Don

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #1 –
Just a few ideas Don,
 Electric tank switching valve in front of existing pump to select flow and a check valve after the existing pump to prevent back flow. These valves are used on dual tank pickups and are reliable. As I know nothing about your system this is just a thought.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #2 –
Don, this is our fuel pressure gauge:

MaxTow 30 PSI Fuel Pressure Gauge

You could also install several senders and switch them to a single dash meter.

Barry

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #3 –
Don-over a year ago I was having lots of issues with my CAPS pump.  I changed filters numerous times and ruled them out.  Finally I decided I needed help beyond my expertise.  I took my coach to Cummins Coach Care in Avondale, Arizona, just outside of Phoenix.
That is the Cummins shop that John Haygarth had his coach worked on about 4-5 years ago after Quartzite.  John spoke highly of them and I decided to try.  They took it back in for diagnosis which lasted several hours.  The answer, it was the CAPS pump, but not the whole pump.  The unit comes in several components and the accumulator part on mine had failed.  Recommendation, replace that part only, it was in stock, but took a whole day of labor so they would work on it the next day.  We slept in the coach and they took it in and fixed it at the price they quoted- a little over 2 CB's with my Cummins Power Club Discount.  Better than 6 CB's.  I probably have put 10,000 miles on it since then and seems to be working fine except recently I am getting some bucking on hard climbing, no stop engine light, so I will probably change filters again. 

I share this with you and all who have the CAPS system that if it gives you trouble, it might not have to be the whole pump replaced, just one part of it.  Finding a reputable Cummins shop with good techs is sometimes hard, but I suggest trying that before replacing a CAPS pump.

Hope this helps and you have a safe journey.                ^.^d

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #4 –
Back in 2015, had a CAPS pump leaking at the distribution head. At the time no one would work on the pump replace only 5800.00 complete pump and labor. Now  seems as though they ( Cummins) will replace components. With that said the fuel filters will cause the issue you speak of, usually just the primary.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #5 –
I had the same experience as Ted. I had a problem with the Injection Control Valve on mine. Cummins 8.3L CAPS ICV - BK Diesel Service Had it replaced at Cummins in Jacksonville Florida. Been working great. I think I was getting the same error as Don but with different symptoms.

Mark

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #6 –
Have you thought about an accumulator downstream of the lift pump or filters it would smooth out any high demand flow impulses.
Not quite sure of the mode of failure of the caps pump but it seems too common for Cummins to ignore for much longer. But hey it's making big bucks.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #7 –
Mark,
Do you know how they diagnosed the bad ICV, did they to the click test using the Cummins Insite software?
Don
Quote from: MAZ –
I had the same experience as Ted. I had a problem with the Injection Control Valve on mine. Cummins 8.3L CAPS ICV - BK Diesel Service Had it replaced at Cummins in Jacksonville Florida. Been working great. I think I was getting the same error as Don but with different symptoms.

Mark

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #8 –
Chuck, I was thinking along similar lines. Though I am not sure that I would need anything but a check valve on the output side of the OEM pump to prevent back flow and maybe one on the out put of the new pump. I could just remove the one on the output side of the Davco 382 and move it to output side of the new pump. Still thinking...
Don
Quote from: craneman –
Just a few ideas Don,
 Electric tank switching valve in front of existing pump to select flow and a check valve after the existing pump to prevent back flow. These valves are used on dual tank pickups and are reliable. As I know nothing about your system this is just a thought.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #9 –
One thing about the Davco 382 is that you can see what's going on. When I first put the Davco on and was still getting the stop engine light, I would pull over and pop the engine hatch to check it out. I would see that the level had dropped in the clear bowl to the bottom of the filter element. My supposition was that the level had gone below the outlet under load because A.) There was an air leak keeping the gear pump from having a hig enough vacuum to not lose prime. And/or B.) The CAPS gear pump is getting weak or there is cavitation because an elbow or a restriction somewhere upstream. There could even be a restriction in the pick up tube in the tank. I think my fuel lines are fine since FOT put new ones in November of 2013. Unlikely to be a kink there as they are the Parker polyamide plastic kind. There could also be an air leak at the fitting on the tank which is pretty well buried in the middle of the top of the tank. I hope not, that would be hard to check...
The fun continues...
Don
Quote from: bbeane –
Back in 2015, had a CAPS pump leaking at the distribution head. At the time no one would work on the pump replace only 5800.00 complete pump and labor. Now  seems as though they ( Cummins) will replace components. With that said the fuel filters will cause the issue you speak of, usually just the primary.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #10 –
An accumulator would probably help, but the only kind I know are the kind I have in the fresh water system. I think it would have to be pretty big to be effective for a long uphill pull. Don't know, but at this point I think my best plan is to give the CAPS pump a constant positive low pressure feed at what ever volume it wants.
Don
Quote from: Old phart phred –
Have you thought about an accumulator downstream of the lift pump or filters it would smooth out any high demand flow impulses.
Not quite sure of the mode of failure of the caps pump but it seems too common for Cummins to ignore for much longer. But hey it's making big bucks.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #11 –
How long did it take Cummins to step up to the  plate on the 5.9 killer dowl pin problems and resolve the issue at no charge to the owner? Guess what I won't own one

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #12 –
I think I read recently (and now can't find it) that the Davco filter system had a lower throughput spec than the Racor filters, like 1/3 less.  Is this a possible contributor to Don's issue? 

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #13 –
I did extensive research on this aspect. The Davco 382 is rated at 180GPH the Racor it replaced was 90GPH. Interesting bit of trivia, Fleetguard (Cummins) OEM's the Davco filters and gives them a different model number. A smaller version of the one I have, Davco 245 is rated at 60GPH by Davco. Cummins has the same unit and they call it a Fleetguard 236 and they rate it at 90GPH. The application guides say the smaller version rated by Davco at 60GPH and by Cummins at 90GPH is suitable for ISC and ISL. The 382 is used on the largest CATS and Cummins ISX's currently. Is it possible that the 382 is too big and the CAPS pump doesn't develop enough vacuum to hold the prime?  That doesn't make sense to me... but I am sure that the throughput of the Davco 382 is more than adequate for the ISC. Also, this issue started before the filter change and was what motivated me to pursue other filter options in the first place.
Don

Quote from: Roger & Susan in Home2 –
I think I read recently (and now can't find it) that the Davco filter system had a lower throughput spec than the Racor filters, like 1/3 less.  Is this a possible contributor to Don's issue? 

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #14 –
Quote from: Don & Tys –
Mark,
Do you know how they diagnosed the bad ICV, did they to the click test using the Cummins Insite software?
Don
Don, Cummins did extensive trouble shooting to rule out fuel issues (reading fuel pressures)and then they sent some data that they captured on the computer to a lead technician somewhere else in the US. He decided it was the ICV. We also took it for a drive with the tech and his computer while he ran tests on the road. I believe the ICV controls the timing.

Mark

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #15 –
Perhaps I missed it somewhere in the long technical thread, but I'm wondering if it would be possible to make the electronic lift pump run continuously, rather than shut off after 30-45 seconds.  Doing this would take the "sucking" load off the main fuel injection pump.

Would have a similar end result to Don's idea of adding a pump to the system - just use the one already in place.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #16 –
I don't know if that pump is rated for continuous duty.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #17 –
I don't know the details of the CAPS system, but pretty much everything I've read seems to indicate it's another word for "headache." Even though it would undoubtedly be expensive,  I wonder if the best solution would be to upgrade to the system Cummins used after the CAPS system.

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #18 –
 I changed the secondary fuel filter before starting out today, and it did seem to help a bit.  After a while  however, I did get the stop engine light for a few seconds now and again.  One thing different today, was that I added a gauge to the VMSPC for fuel temperature. I have no idea where the sensor for that is, but I suspect it is in the caps pump array somewhere. Anyway, the fuel temperature slowly crept up and finally settled in  between 150° and 160°. I have no idea what is normal for that sensor, but the VMSPC has a default red flag at 200°. I will have to do some more research, but I am pretty sure that I read that cavitation happens more easily at higher temperatures.  Our coach has a fuel cooler in front of the radiator and a little manifold mounted on the frame rail on the pump side of the engine.  I believe there is one 90° elbow on that manifold that I could eliminate which might be an incremental help. I have eliminated a couple of other elbows because from what I have been reading, elbows are very detrimental to flow dynamics.
Still thinking... thanks for the input!
Don

Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #19 –
Don,

If you already have a fuel cooler plumbed in, if you determine that a larger one is needed, should be an easy switch.

Hayden makes a number of different, quality air to fluid coolers.  And, agree cool fuel= happier engine. 

No idea where your temperature sensor is located, but a pretty reasonable "gut check" for fuel cooler efficiency is to compare fuel tank temperature to ambient temperature after driving several hours. Particularly telling when below 1/2 tank.  With the fuel cooler in the return line doing its job, you really want to see a minimum rise over ambient.