FUEL IN OIL 2010 CUMMINS ISC 8.3

The HEST lamp will usually be set to come on above 500F and below 5mph. Nothing concrete to go off of here except that the exhaust was hot. Did it complete a passive regen? Stop in the middle? or just start one....... No way to know. This is why you need to review the regen history.

This is a toss up IMO. Engine fan running continuous does tend to keep things from heating up engine wise but you also have the increased load of the fan on the engine. Either way this should not be a big enough issue to be the root cause of frequent regens.

Face plugging DOC and DPF soot blocked are going to be the result of the failing injectors if they are determined to be the root cause of all your troubles with the fuel dilution. Do we know when or if it has ever been serviced?The regen history will tell a story of what is going on in the aftertreatment. If it really is regening even once a day it is too often IMO. I would say given the application on a healthy engine and DOC/DPF you should be around the 20-25 engine hour mark for regen frequency. I would be getting the DOC/DPF apart for inspection and performing the snap accell test I suggested in my previous post. Heavy is correct that DOC's can lose their platinum washcoat over time causing poor temperature rise.

If your regen history shows troubles getting up to temp and regens every 5 hours the oil will be getting fuel diluted much quicker than normal. Does this truck run OK? Does it have any history of CEL coming on? If so what faults have been logged? I know you said this truck has an idle timer set but then drivers defeat them every day.......this is why I asked for total engine hours? Please post ESN and we can look deeper into TSB's and injector updates that may apply to this engine.

 

Now we are getting somewhere......You need to troubleshoot the fuel system rail decay as you have a leak somewhere in the high side common rail. One of the injectors, the relief valve , or the fuel pump head is leaking causing the decay. Check the relief valve first, it should have zero leakage and I see alot of them fail and go from there. Its the easiest to check and the cheapest to fix as well.Get the rail decay solid and get that IPT test to pass. I highly recommend a reman filter versus cleaning, but make sure you get the fuel system squared away before you put it all back together.

I will look into tsb's and update with more info later on.........Engine software level?

 

That fuel injector performance test is quite telling.
I am willing to bet your issue is a cracked injector.
I have seen this many times with common rail Cummins.
Remove the valve cover start it up plug in and run the test that runs the rail pressure all the way up and get a light and check each injector.
You should not have any problem seeing fuel spraying out of the bad one.
They usually crack up the side.

 

Yes, this is the pressure relief valve. Flow from the return of this valve should be zero (I believe the spec is in drips per minute) during the fuel system leakage test. You should have no fuel coming out of this valve during the test. You can replace it and recheck the rail decay if you choose to.

Complete system diag steps are found in the Service manual on QSOL - fuel system Diag.section 005-236

If it comes down to injectors-they want you to measure return flow and cap each injector. This is a valid test. I'll be the first to admit , I usually cheat on this and just time the rail decay during the test with each injector capped and note the changes to the decay time for each injector. If you cap one and it holds steady, you found your bad one. There will be some fluctuation in the rail pressure sensor but for the most part it should hold pressure.