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dale1 · 12-20-2021, 07:14 PM

CAPS Pump Failure.

We have a 2001 Holiday Rambler with a Cummins ISC engine with 92k miles I purchased it 4 years ago. It had been sitting for a number of years, and I was unable to recovery any maintenance history.

After tires and the basics came good times. We put over 8K miles traveling to North GA and NC.

Six or eight months ago, we started with having a sporadic Stop Engine Light under high engine loads. At first it took full throttle to make it come on. I could make it go out by letting up just a little. It always ran well and started good. Cathy's Mother was passing at that time, so I didn’t have much time for maintenance. I called 3 or 4 mobile technicians. I was told just plain no, to I don’t have time, to I'll get to it when I can was the responses. One guy came to the coach and scan it. You can see those results in another post. It didn’t help.

In the meantime, it became progressively worse. It started to “de-rate." Going from 68 to 45 in a few seconds on the interstate is bad. Feeling desperate, I started reading other posts and changing parts that I felt comfortable with. Fuel filters, and sensors, etc. Then I discovered a cracked manifold and sticking turbo. I was sure that was the problem because the Low manifold pressure and manifold team codes matched that. I changed both the turbo and manifold with not resolve. Thanks to Jim, he led to a possible overflow tank problem. Mine was defective and the hose going to the tank was clogged. I was sure this time. However, I Installed a new metal tank and hose. Still No help. At this point, I’m at approximately 20 hours of time and 2 grand in parts.

Next came the lift/transfer pump. No change. Then I installed a FASS pump. I like the way it works, but it did not fix the problems. It starting de-rating, had lower power, and a stop engine light more often. Still "NO Codes"

At that point I knew I needed real help, but was afraid to travel to the nearest Cummins network shop. In my case over 100 miles to Savannah and Albany Georgia. I was afraid that it wouldn’t make it that far without a total shutdown.

Somewhat of a hard decision was made and we ordered the Caps Pump. Cummins Accumulator Pump System. $4200 bucks with a $1200 core. Hoping it would fix it I spent most of my free time after work and weekends for 3 to 4 weeks. 20 to 30 labor hours later, its changed. I was shocked how fast the engine started and how much different the engine sounds. It is noticeably quiet. There used to be a bass drum sound coming from the intake port on the outside of the coach. That sound is no longer there? It runs smother, and has more power. Maybe it is attributable to the new turbo also, I don’t know? Ron was a big help with tips and tricks on how to troubleshoot and change the pump.

Would I do it again? I don’t know? I would try to find someone first. I’m I glad it is done? Absolutely. She got a lot of parts included the upgraded Fass Pump fuel pressure gauge. We put it to work this weekend. 300 trouble free miles. If feels strong and I have more confidence in it now. Special thanks to Ron and Jim for providing really good information. Dale

barmcd · 12-20-2021, 08:02 PM

That was an ordeal. Glad you got it sorted out in the end.

jacwjames · 12-21-2021, 06:41 AM

I followed your post everyday and felt your pain.

This should be a wake up call for owners who have the CAPS pump. Fist sign of a problem with my system (a leaking lift pump) I installed a FASS system. Hopefully I was proactive enough to have avoided your type of problem. Time will tell.

Glad you got it fixed and hope you have time to enjoy the efforts of you work.

dale1 · 12-22-2021, 07:17 AM

You know Jim. That is what I as trying to say without sounding like a "know it all"

IMO, If you have an ISC motor you should consider the pump as part of the maintenance schedule. Its only a mater of time before it fails.

That is the same thing as saying. "oh, those 12 year old tires are not going to blow out. they only have 8 thousand miles on them"

dale1 · 12-22-2021, 07:19 AM

Hey, on side note. I have 17 1/2 psi at idle. However, i experienced as low as 15 psi under full throttle? have you seen that, or any thoughts? thanks

jacwjames · 12-22-2021, 02:12 PM

Mine sits at ~16 psi at throttle.

Under hard pulls I've seen it drop to ~13 psi.

I did leave my primary fuel filter in place so it actually pushing fuel through 3 filters to the injector pump and the one return back to tank.

I've put ~10K on my coach since install and have not seen any appreciable change. I will probably change my fuel filters before my next big trip and may also remove the original primary filter.

jacwjames · 12-22-2021, 02:43 PM

Quote:

Originally Posted by dale1

You know Jim. That is what I as trying to say without sounding like a "know it all"

IMO, If you have an ISC motor you should consider the pump as part of the maintenance schedule. Its only a mater of time before it fails.

That is the same thing as saying. "oh, those 12 year old tires are not going to blow out. they only have 8 thousand miles on them"

I knew this was a potential problem so I kept an eye on mine, even bought a spare gasket if I got stranded on the side of the road.

Then one day last year I took the coach for a ~60 mile drive and filled it up with fuel. The next day I crawled under the rig to clean the stems on the jacks as they came up really slow the day before. First thing I saw was a small stain in the new concrete right under the starter, checked closer and sure enough the lift pump was leaking. Went up on top and tightened the 3 bolts.

Then I ruminated on the issue for several months while I was doing other things (building a new garage etc) and earlier this year after reading more and more posts on CAPS failures I decided to just go ahead and install a FASS transfer pump and completely bypassed the old lift pump.

No doubt in my mind this was the right thing to do!!!!

dale1 · 12-22-2021, 06:16 PM

Yea. i really like the idea of the FASS pump. 30 feet is a long way to pull fuel through a hose. The system was depending on the Caps pump to do that after the lift pump ran for about 45 seconds, then the caps pump takes over. the Fass is running all the time pulling fuel from tank and sending it over to the caps pump with 6 to 8 feet of hose distance.

On another side note. i was going to remove the lift pump until i studied the a manifold on top of the lift pump. it does 2 important things. 1. it has a check valve built into the housing. that is helping to keep the Caps pump supplied with fuel. 2. it has the return line connections to allow the unused fuel to cycle back to the fuel tank. As you know recycling the fuel from the tank to the pump facilitates "polishing" or filtering. As the Fass pump does that as well. I guess it cant over do that. Maybe is unnecessary redundancy, IDK?

thanks again for all of the helpful information. i appreciate it.

Timaz · 12-23-2021, 06:45 PM

A few of you guys may remember a post of mine last summer asking about the stop light coming on during the end of a long grade...Well as the same guys here most likely saw my other post last month when I lost my caps pump...I guess Dale1 hit the mark. But in my case I'm not sure there was much in the way of loss of power.

Tim

dale1 · 12-24-2021, 08:11 AM

Tim, your right. I tired to say that while being somewhat polite. It was extremely stressful when it started giving problems. A diesel mechanic told me it was the pump 6 months ago when I mentioned the light to him. He said, If the Pump fails it will not run. I started reading other opinions about filters etc. Became distracted, and put off the inevitable. I wish I had found your post earlier.

Sspdiesel · 12-25-2021, 07:58 AM

The most important as my fathers always said either you pay now or you pay more later ..

Dale
You did a good job swapping that pump .. it’s not that easy ..but you got it squared away and in the end saved others on site to tell them to install fass system before caps fail.

I just ran mine 1300 mikes knock on wood ran like a Cummins …sitting in the sun .
All good enjoy merry Christmas
Rob.

Ps make sure you add fuel additives ..

Timaz · 12-26-2021, 10:01 AM

Rob,
As you may have seen in my post about losing my cabs pump the Cummins mechanic that replaced it said it was upgraded from the original so the same failure won’t happen again. Is this true?

Tim

jacwjames · 12-26-2021, 10:29 AM

Tim
Was your lift pump replaced?? This is what really causes the CAPS pump failure.

Caliber · 12-26-2021, 11:29 AM

Quote:

Originally Posted by jacwjames

Tim
Was your lift pump replaced?? This is what really causes the CAPS pump failure.

Ultra low sulfur fuel is the major cause of fuel pump failures. Diesels built before 2007 where not designed for the low sulfur. The sulfur added lubricity to the fuel. Cummins updated the pumps to handle ULSD.