Cummins ISC issues were not CAPS related

May 08, 2019, 03:59:07 pm

Recently I have been having issues with my Cummins ISC- bucking , missing, blowing puffs of black smoke, abnormal fuel pressure codes on my VMSPC, but no engine de-rating. Sometimes this happened under load climbing , other times on level ground. Very nerve racking while in a construction area, no place to pull off and wondering if the engine will die right there- thank God it didn't.

At first I thought this was fuel related- had my fuel and tank professionally cleaned by Keith Risch in NAC- ran if through a 5 micron filter twice. Changed fuel filters, air filter- coach ran great- thought my issue was solved until it happened again. I added biocide and fuel injector cleaner, changed fuel filters 2 more times, still having issues. Then I thought it was my CAPS fuel pump- I had replaced the accumulator for that pump in November 2017 but the pump is original so..........?

I took the coach into Cummins Coach Care in West Chester Ohio, just north of Cincinnati. I have used them before with success. I explained what was going wrong and what I had done so they had a baseline of the issue. The Cummins Insite system had codes for fuel pressure errors, found a bad wire and a sensor that was reading incorrectly even with the ignition off. The tech replaced the pressure sensor part # 4025130 and surge suppressor part # 3944110 and did some electrical repair on the wires. The explanation is that the wrong pressure readings going to the ECM caused the ECM to try to compensate for the bad readings ( high and low pressure) which caused the issues with the engine. Coach is now running very well and with my Cummins Power Club I got out for less than 1.5 coach bucks- well worth it in my view.

This is another example of trying the simple things first- fuel filters, biocide, cleaner, etc, but when I reached the end of my expertise it was time for the experts. I am really glad it was not the CAPS pump.

I always encourage everyone to carry spare fuel filters for your engine and generator. I have gotten pretty good at changing filters myself, but if you don't want to or cannot, if you have the right filters with you it will help you out greatly when you do have a fuel filter issue.

Be safe and cya down the road.

Re: Cummins ISC issues were not CAPS related

Reply #1 – May 11, 2019, 09:30:04 pm

Ted,
I am glad to hear that this issue has finally been resolved! Replacing the pressure sensor and possibly the surge suppressor are on my short list of of possible causes of the stop engine light. I haven't experienced the issue since leaving New Mexico after changing the secondary fuel filter, but I am not convinced that I am done with it yet. Thanks for the part numbers, they appear to match up with what I had researched. The parts are not expensive, but my next step will be to install a fuel pressure/vacuum gauge with a dash mounted gauge and a sending unit. I haven't identified a suitable unit yet, or I would have done so already. I may change out the pressure sensor at the same time, but I may want to see what the pressure gauge is showing if/when the stop engine light goes on. I don't want to change to many factors at once. Anyway, I am happy you are done with that vexing issue!
Don

Re: Cummins ISC issues were not CAPS related

Reply #2 – May 12, 2019, 10:45:51 am

Don- thanks for the follow up. The interesting thing about my pressure sensor was that it was giving off false readings with the ignition off. So was the fuel pressure really off that much or just the electrical signals saying it was? The tech seems to think it was just the signals to the ECM. He also replaced some bad electrical connections on the sensor and surge suppressor which might have contributed to the issues. Older electrical wires, connections, sensors, 163000 miles, etc........all contributed their part. With your clean fuel, Dave filter and new secondary filter I hope you have no more problems, but these are a few more areas to look at if you do. Safe travels to you & Tys.

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