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Old 05-09-2022, 12:15 AM   #1
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Can Common Rail Fuel Pump Leak Cause Exhaust Smoke

My 2007 Holiday Rambler with Cummins ISB 325/5.9 common rail engine smokes at idle. The smoke occurs whenever at idle cold or hot. It is not visible when driving and the engine performs normally when driving. I know, most commonly an injector problem.

After several hours troubleshooting including new fuel and air filters and injector testing my local service shop mechanic found an EGR valve code and replaced it. Still smoking. After more troubleshooting the shop then contacted Cummins directly. Cummins provided an extensive troubleshooting checklist which the mechanic followed to the conclusion that my problem is an internally leaking fuel pump. My mechanic has assured me that Cummins directions support his tests that my injectors are not the problem. He says that a new injector pump will stop my smoke.

Is it possible for a leaking injector pump to cause smoking with a common rail system? Should I go ahead and have a new pump installed?

As I understand the common rail system the injector pump supplies the common rail with pressurized fuel, fuel then enters the cylinder only when an injector opens. I can't see how fuel from a leaking pump could cause the engine to smoke. I generally believe it wise to pay attention to the opinions of professionals we hire for their opinions. In this case I am definitely not qualified to dispute the opinion of an experienced diesel mechanic derived after following instruction from the engine manufacturer. Still, this one has me wondering. I wish I had the option of a second mechanic's opinion but in this case several factors dictate that would be very difficult.
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Old 05-09-2022, 01:02 AM   #2
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I'm more likely to think you have oil leaking in from your turbo. Also verify for us that your Turbo has a speed sensor; and if so clean it.

Your CAPS-2 system is a HPCR type. As such, it uses the same CAPS injection as as CAPS-1 system but, but in your CAPS-2 there is no STATOR or Fuel Distributor, because you have a common rail to deliver high pressure to so-called smarter injectors.

By smart, I mean your ECM controls the timing vs. in CAPS-1 the timing was controlled by the Stator and a rotating fuel distributor system to "dumb" injectors.

So if you don't have oil leaking into your turbo intake (which is only a 30% chance) then I would bet you have a stuck fuel injector which is more common with 2005-2006 RVs with a HPCR system. And since it's only smoking at idle, think you might get away with a Seafoam cleaning.

Note: Cummins replaced the HPCR in 2004-5 with a HPFR system in 2007 (RV models) and this type of system is still in use today.

Also, the HPCR lift pump (CAPS-2 system used in late 2004-6) is different than the early 2004 CAPS-1 lift pump system. Still, the only purpose of both lift pump types are "to start the engine." So if your engine starts and keeps running, which you say it does, then I would NOT be focused on the lift pump as the problem.

====

What color is the smoke? I assume it's black?

How many miles are on your engine?

===

Seafoam Tip: Fill a fuel filter with sea foam and start your engine. It will smoke a lot at first and then that white smoke will go way. ...And maybe, if you are lucky, all will be good again. ...And seafoam will not hurt your engine.

Tip #2: If that does not work, add Seafoam to your fuel and drive for 200+ miles.

Tip #3: You might also consider adding Seafoam to your engine oil just before an oil change. This is to clean the carbon off your piston rings among other things. Then drive under light loads for 100-150 miles, and then change your oil. It's all good preventative maintenance.

===

One last point: RV delivered in 2005-6... some owners find their fuel hoses are deteriorating due to USLD fuel eroding away the inside of the fuel lines, which seem be made out of a different material than those hosed used in 2004 and earlier. The problem is that with these 2005-6 hoses, the rubber inside breaks down and creates internal "flappers" that cause diesel fuel to "foam" and that causes problems with the HPCR pressure sensors.

One solution is to replace the fuel lines which is expensive and is a PITA. The other solution is to install a FASS or AIRDOG electric fuel pump; and I think the AirDog pump maybe a better way to go for your type of CAPS-2 pump, but I'm not sure about that.

Other than these fuel delivery concerns, the ISC/ISL is still a great engine.
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Old 05-14-2022, 06:33 AM   #3
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BMU-Scotty, thanks for the very complete answers. I apologize for the late response. You were right about a stuck injector. The first injector test was only a cut out test. Following your advice led to isolating injectors to test for leaking. The Seafoam corrected the smoking briefly. It has 124,000 miles so I decided to replace all the injectors. No more smoke.
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Old 05-14-2022, 07:52 AM   #4
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Thanks for the tips on using Seafoam, first time I've seen this. Do you have a source of your info, is this best practice recommended by Seafoam and/or Cummins.


Thanks for the followup as to what cured your problem. Glad you got it fixed.
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Old 05-14-2022, 09:37 AM   #5
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I just Googled Seafoam. It is widely available at auto and marine supply places.
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Old 05-14-2022, 10:10 AM   #6
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YUP, you can buy it pretty much everywhere. Never heard of pouring it directly into a fuel filter.



I use it in my same engines; chainsaw's, mower, brush mower etc.
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