Cummins 6.7 Ottowa Spotter DPF

[marka683]

We are getting check engine light and limp home for the DPF clogged with soot. issue was occurring every 4 to 5 hours of run time, forced regen cleared the code and unit was returned to service. DPF was replaced, we went 500 hours and the issue returned, same code, limp home, forced regen, back in service. The repair tech says the engine needs replacement because at 23,000 hours it has exceeded the manufacturers recommended lifespan. I do not buy it. Any advice on where to go? The year of this machine is a 2018

Thanks

 

[Truck Shop]

Depends on percentage of blow-by. DPF does not like oil.

 

[Birken Vogt]

Offhand I would say that is a huge number of hours. Does this thing work 2 or 3 shifts continuously since 2018? Does it ever see a good load or does it putt around the yard all the time? Does Ottowa have any advice about it?

 

[marka683]

Lots of idle time, three shift operation, each load moves about two miles and it must get up to 45 MPH for about a half mile.

 

[Birken Vogt]

I am hoping somebody more knowledgeable will chime in, but we use these on generator engines as well, and we figure that 1 hour roughly equals 35 miles of operation, so 23k hours would roughly equal 800k miles, seems to me like it served its time and now it is time for rebuild/replace, everything inside is probably worn slick, that is why the guy does not want to mess with it, fix one thing and then within a few weeks/months something else will go out and he might get blamed.

 

[Truck Shop]

I am hoping somebody more knowledgeable will chime in

I think you covered it.

 

[skyking1]

^ what they said. The CRs are not happy with all that idle time. Keep running it if you can, and it will start breaking rings that are carbon-backed.
In farming terms, it has hoed it's row.

 

[terex herder]

Somewhere in that computer there should be a total for the gallons of diesel burned. It would be interesting to see what the average duty cycle has been on this engine. I'd guess its pretty light.

35 mph for gen set engines? Sounds way to low to me even if they are unloaded stand-by. Unless you are running funny frequencies, those are hours at 1800 rpm. There again, fuel consumption would be useful.

 

[92U 3406]

Sounds to me like its burning oil and clogging the DPF. I wouldn't be suprised if the cylinder walls were polished smooth.

 

[Nige]

The repair tech says the engine needs replacement because at 23,000 hours it has exceeded the manufacturers recommended lifespan.

At 23k hours I would say it will be comprehensively Donald Ducked. Quite frankly I’m surprised that it has lived that long. Usually it’s only big engines that get to that sort of hours. As TH said have someone get into the electronic control and find out how many gallons/litres of fuel it has burned in its life so far.

 

[cfherrman]

Have you tried high idle instead of just idling?

 

[pushbroom]

The medium duty cummins are famous for having failed injectors which produce too much soot causing the dpf to plug early. Remove the exhaust before it enters the dpf and have someone floor the throttle. There should be a puff of smoke when the engine is revving up then clear at full throttle. Puffs of black or grey while at full throttle point to injector issues or air handling issues.
Idling that much I would assume the grid heater is plugged solid with soot as well as the egr components.

 

[John C.]

Disconnect the crankcase ventilation if possible and measure crankcase pressure. Got an oil sample and analysis.

Those hours are very high for that engine. Light load is actually detrimental to a diesel engine. They don't wear out from metal touching metal. The wear is caused by acidic compounds formed from incomplete combustion that settles on the walls of the cylinders. Lots of idling and light work shortens diesel engine life. You basically hit the jackpot on that engine.

 

[skyking1]

^ it's why I caution anyone about buying a work truck out of the Dakota oil fields. Cold weather = too much idling. The miles might be low but if you dig into the display the hours are waaay whacked.

 

[Truck Shop]

I said that right from the start, percentage of blow-by.

 

[Birken Vogt]

35 mph for gen set engines? Sounds way to low to me even if they are unloaded stand-by. Unless you are running funny frequencies, those are hours at 1800 rpm. There again, fuel consumption would be useful.

That is a number I have come to, from experience. I can equate the degree of "wore slap out" of a generator engine with the equivalent you would expect to see in a car with x number of miles. Usually the ratio is 35 mph, plus or minus a lot.

Probably the fact that it runs for many hours at 1800 and never changes, is helpful.

 

[terex herder]

Your comparison of "wore slap out" from a gen set to road vehicle seems as legitimate as it can get for two vastly different loading schemes.

 

[skyking1]

I imagine it involved a few piles of parts and chickeneye. Wore slap out

 

[Nige]

We used a factor of 30 between off-highway equipment hours and on-highway engine miles. Like BV it was +/- a factor of quite a bit but it was generally pretty close.

 

[marka683]

This is the most recent report from the service contractor, this seems like what has been described here. Thank You all for your input.

FOUND CODES FOR EXCESSIVE REGENERATION CYCLES AND LOW EGR FLOW REMOVED EGR DIFFERENTIAL PRESSURE SENSOR AND FOUND OILY SOOT ON EGR SIDE, CLEANED PASSAGES AND REINSTALLED SENSOR REMOVED CHARGE PIPE FROM TURBO, NO EVIDENCE OF OIL PRESENT RAN UNIT WITH OIL FILL CAP REMOVED, UNIT SMOKES THROUGH FILLER HOLE DUE TO COMBUSTION BLOWBY SUSPECT EXCESSIVE CYLINDER WEAR CAUSING INEFFICENT COMBUSTION AND EXCESS ENGINE SOOT PRODUCTION EXCESS SOOT PRODUCTION IS CLOGGING EGR COOLER AND CAUSING EXCESSIVE REGENERATION CYCLES TO CLEAR SOOT FROM DPF ENGINE HAS 23437HR, USEFUL LIFE EXPECTANCY IS AROUND 25K HOURS ENGINE IS NEAR END OF USEFUL LIFE AND NEEDS REPLACEMENT