Midnightmoon
Senior Member
New dpf, new sensor, new doc so what would cause high temp downstream of doc? deutz tier 4 700hrs? temp climbs at post injection
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High downstream doc temp
- Thread starter Midnightmoon
- Start date
funwithfuel
Senior Member
That's what its supposed to do. Dosing fuel onto heated DOC causes raised exhaust temps to begin breaking down soot into ash.
Midnightmoon
Senior Member
It's high out of spec causing code 4766 fmi 0
funwithfuel
Senior Member
What's it in? Volvo/Deutz had issues with temp sensors. Can you see actual values, or are you going by the code and FMI?
Midnightmoon
Senior Member
Case temps were 540-550 (target 589) then raises to 600-630 then back to 540. I need to swap sensor to confirm its good. Was getting 1455 deutz said doc no good new doc installed now I'm getting 1029 doc high temp downstream. Going to be a few days before I can do more diagnostics
funwithfuel
Senior Member
I would be more concerned with fuel dosing. Does this have the little torpedo heater in line downstream from the turbo, or is it running a 7th injector. A pic of your exhaust would be helpful.
Midnightmoon
Senior Member
It's a deutz 4.1 L4 serial 12074167
No torpedo heater or 7th injector.
It's overfueling or eating coolant just a shot in the dark if someone's had similar issues with these codes. During regen it's under temp then over temp
No torpedo heater or 7th injector.
It's overfueling or eating coolant just a shot in the dark if someone's had similar issues with these codes. During regen it's under temp then over temp
funwithfuel
Senior Member
If your EGR is leaking coolant into the exhaust stream, its gonna foul your DOC. The coolant bakes on the DOC and becomes an insulator preventing the elevated temperatures. I'm more inclined to think you've got a bad injector. Just my opinion.
BigWrench55
Senior Member
X2 what FWF said. if you are seeing temperature rising and lowering like that. There is unwanted fuel being ignited and heating up the doc to much. The computer see's that happening and stops dosing fuel to lower the temperature. What is the temperature before the doc when this happens? Will the machine go into regen on its own or is the soot load too high and it needs a forced regeneration? If you can get it to go into regen on its own. Then try stalling the hydraulics to get a load on the engine. If you can do that while in regen and keep it up until it finishes without coding out. Then you have unwanted fuel getting into the exhaust. If you don't have a burner then the engine is probably firing fuel on the exhaust stroke to raise the exhaust temps. You can have any one injector leaking fuel into the exhaust. Do you have any fuel related codes active or inactive?
Midnightmoon
Senior Member
No fuel related codes. Coolants not the issue 20 minutes after I installed the new doc I got high temp at downstream doc. Before all this dpf was plugged and replaced then plugged in 15 hours. I wasn't working on it then. I'm thinking sending injectors out is next step after some more testing and maybe getting it to regen on it's own. Thanks. Monday I'll have some more info
funwithfuel
Senior Member
Does this machine have an intake throttle? How about the air cleaner and turbo? If you're soot loading too soon or have raised DOC temps, it could be starving for air. Have you checked the overall condition of the running engine? Any way to vent the exhaust so you can see what your smoke looks like under load?
Midnightmoon
Senior Member
Checked with exhaust pipe removed no smoke but I'm wondering if a injector could be leaking and not show smoke . Engine was just serviced new air filters oil ect.
funwithfuel
Senior Member
When you checked smoke, was it full throttle under load and at operating temperature? Is there any chance of plugged or backwards air filter? How about ruptured charged air cooler or boost pipes? Do you have boost, is it VGT or maybe a stuck wastegate?
Only 700 hours, any history of water in fuel?
I did have an excavator, ran like a top. Good power, no engine codes. This thing passed smoke test for three of us. I camped out at the jobsite to observe the machine in operation. Every now and again, this thing would fog the area with rich grey smoke. Ultimately, we elected to replace the injectors. That was last year. No evidence in the injectors as to what was wrong. It was very difficult to replace something when I couldn't prove damage. What gave it away, immediately after parked regen, I pulled arm in and bucket over relief. Watching exhaust temps. DOC and DPF inlet were shooting up as if in regen. Temps were indicative of active regen 1100°F to 1300°F in less than a minute vs slow increase during regen. Injectors were the root cause for me.
With only 700 hours, isn't there any warranty consideration? Good luck.
Only 700 hours, any history of water in fuel?
I did have an excavator, ran like a top. Good power, no engine codes. This thing passed smoke test for three of us. I camped out at the jobsite to observe the machine in operation. Every now and again, this thing would fog the area with rich grey smoke. Ultimately, we elected to replace the injectors. That was last year. No evidence in the injectors as to what was wrong. It was very difficult to replace something when I couldn't prove damage. What gave it away, immediately after parked regen, I pulled arm in and bucket over relief. Watching exhaust temps. DOC and DPF inlet were shooting up as if in regen. Temps were indicative of active regen 1100°F to 1300°F in less than a minute vs slow increase during regen. Injectors were the root cause for me.
With only 700 hours, isn't there any warranty consideration? Good luck.
Last edited:
Midnightmoon
Senior Member
Turned out to be 2 bad injectors