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Topic: Cummins ISC CAPS intermittent stop engine light (long!) (Read 4764 times) previous topic - next topic

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

Reply #25 –
In engine training from Detroit Diesel, they told us in their research, 80% of the stop engine light engine warning instances in their indestry, were not critical,  and were due to faulty failure codes, mostly due to failed sensors.  I hope this is your case.

That was why MBZ was instituting  their data load upload to the factory for them to quickly analyze, from their long haul truckers engines with GPS installed and call back service to the trucker.  That way, their engineers could analyze the "warning" and respond d posibly saving the trucker time and money.

I never had any follow up training, so I am not sure how that program went.
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Prev: 1990 Barth, 10L 300 2 yrs; 91&92 Monaco Signature, 10 yrs, 10L C 300 &  6C8.3 300; 1997 ForeT 6C8.3 325 since May 2017.  Employed by Guaranty RV 14+ yrs.  Former VW New Car Dlr/Service Dlr, Sales Mgr, Rv Sales, and Service Adviser from 1968-2017
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Re: Cummins ISC CAPS intermittent stop engine light (long!)

Reply #26 –
A lift pump not working up to specs would explain both check light and higher than expected fuel temperatures.

And, a lift pump is a LOT less $$ than allowing it to take out the CAPS pump.  Again, a fuel pressure gauge would be your diagnostic friend.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
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Chairman FMCA Technical Advisory Committee 2011-2020

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

Reply #27 –
I am definitely going to install a fuel pressure gauge before the CAPS pump. I would like to put one in that includes vacuum so I can get a baseline for the restriction level before I put in a HD lift pump. One of the peculiar aspects of the Cummins CAPS system is that the lift pump is only active for 30 seconds after the ignition key is turned on, basically just to prime the gear pump part of the CAPS system. If the lift pump doesn't achieve prime, it will throw a check engine light with a different code, not the stop engine light which goes away as soon as the code becomes inactive that I have been struggling with. A diesel pusher with the tank up front presents a less than optimal environment for supplying the injectors. That is a long straw to suck fuel through for any gear pump... To me, since Cummins abandoned this setup after only four years or so in favor of the common rail system, that amounts to a tacit admission to the "Achilles Heel" inherent in the CAPS system. However, the CAPS system functioned without an issue for 17+ years and 150K miles in our coach, so I will have to give Cummins a C- on this one...
Don
Quote from: wolfe10 –
A lift pump not working up to specs would explain both check light and higher than expected fuel temperatures.

And, a lift pump is a LOT less $$ than allowing it to take out the CAPS pump.  Again, a fuel pressure gauge would be your diagnostic friend.
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

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

Reply #28 –
This thread is over six months old, so I will quote the relevant part of the original post and add an update the topic. I believe I may have finally solved the issue causing the intermittent stop engine light. There is no way to know how prevalent CAPS pump fuel starvation caused issues are on the 99' through 05' ISC's and ISL's or thereabouts are, but my gut feeling is that this is could be a root cause for check/stop engine lights, loss of power, rough running under load, etc. At this point, now that I believe I have had some success with an approach I first considered more than two years ago. I have been on a campaign to reduce restrictions and improve the fuel supply plumbing in an attempt to keep the CAPS pump happy. Our issues with the fuel system started with a load of bad diesel five years ago. I was able to address the issue initially by changing the Racor primary filter several times and somewhat less frequently, the engine mounted Fleetguard FS1020. After so many filter changes, I got tired of the inconvenient location of the Foretravel OEM Racor RP90. I rearranged some of the fuel supply plumbing and installed a Davco 382 fuel filter/water separator at the rear of the engine compartment just above and to the right of the air dryer. Not only a whole lot more convenient for filter changes, this location satisfies Davco's installation guidelines that the cartridge be mounted at or above the fuel fuel level of the tank for optimum results.
Since the Davco didn't solve the stop engine light issue, I went on a mission to eliminate the 90º elbows in the fuel line plumbing to reduce potential restrictions. The fuel cooler loop itself had five 90º elbows. The suction side had three. That did seem to help some, but the problem persisted. In looking for possible sources of air leaks on the suction side of the fuel system, I noticed that there was one OEM fuel line that Foretravel had not replaced. I found the Cummins replacement part with the QuickServe Online and ordered it. It was about $60 for a 1' braided fabric covered rubber hose with crimped on fittings. Since it was covered in braided fabric, it was impossible to see if it was deteriorated inside. Since it was the supply hose for the CAPS pump coming of of the secondary filter and it was over 20 years old and subject to a lot of engine heat, it seemed a prime suspect for an air leak. It helped some, but again didn't completely solve the problem. Next step, I bought a FASS UP95 (95gph) from Brazel RV Performance. Although the same model number pump could be had from other authorized dealers for almost a hundred less, Brazel adds a relay pigtail that plugs into the old lift pump circuit and makes the Cummins ECM think that the factory installed electronic lift pump is doing its thing and that thing is to prime the gear pump when starting the engine. I suppose that the added part is just a switch with a resistor in line to tell the ECM that there is a load on that circuit. Al, the tech guru at Brazels, says that they modify the wiring harness for this application. I imagine that the modification process just means installing a longer pigtail on the pump. They also modify the instructions to reflect the differences between the ISC and the more common Dodge, Chevy, and Ford PU applications the FASS pumps commonly used on. Bottom line is I felt I could save time by buying the FASS pump from Brazel at thier value added price of $599. At least getting it in Oregon from Brazels saved me sales tax.

To cut to the chase, I installed the FASS UP95 HD lift pump in an RV park and we had our first stop engine light free travel day that involved any sustained grades. It was only about an 80 mile drive, so I don't consider it a definitive test, but it was a definite improvement on the status quo. I also upgraded the fuel cooler at the same time, but I am convinced that the FASS pump has improved matters. Time will tell, but I am fairly optimistic at this point. I will post some pictures of the fuel pump, fuel cooler, and Auto Meter remote fuel pressure gauge install in another thread at some point.
Don

Quote from: Don & Tys –
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.
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson