jwmcgregor Posted July 17, 2018 Share Posted July 17, 2018 I have a US7 MP8 in t 2010 CHU. Not spark assisted DPF setup. I've taken care of and have now got no fault codes showing up on the engine. Soot level showed 90%. When I force a regen through TEXA I get a slow clime to about 600 deg on the front side and the back side stays 50 to 55 deg cooler through the process. I am seeing the dosing module status at 100% but no increase in temp. I tested the DRV supply pressure with my thumb at the DRV valve and It builds plenty of pressure rapidly once regen is initiated. I supplied pressure to the DRV valve when i had it removed and it operates smoothly. I find no sigh of leaks. I removed the dosing module, cleaned the tip and initiated a regen. The nozzle immediately puts out three bursts of fuel then nothing so I cancel the regen. The system completes the regen process without any errors but never reaches temps over 600 deg and soot level is higher at the end of the process. I run VGT test and I can hear the actuator traveling through it's stroke and back. EGR position says zero when truck is idling but i can't see it's position while running the regen. Pressure to the dosing module shows similar to pump pressure when the truck is idling but I can't see where it's at while running a regen. Don't know what to do next...Trying to avoid taking it in to the dealer for what seems to be a $2000 minimum fix. I purchased four of these trucks and I'm working through issues with each of them. Love the trucks and the way they are set up...struggling with the emissions stuff. Any Ideas or dirrection? Thanks Quote Link to comment Share on other sites More sharing options...
turckster Posted July 18, 2018 Share Posted July 18, 2018 Your temps are slow to rise and never reach proper temps? is that correct? Problem could be egr valve never closing. Best check is to unplug egr valve electrical connector, removed egr tube that crosses the valve cover(since it the easiest to remove). Start the engine and there should be hardly anything coming out egr venturi outlet, you can hold your hand over the outlet with no resistance. We will attach a nitrile work glove on the outlet, with the engine running if it blows up and pops withing seconds you've got a bad egr valve. The egr gas will keep the exh. from reaching proper exh. temps during the regen. 1 Quote Link to comment Share on other sites More sharing options...
jwmcgregor Posted July 18, 2018 Author Share Posted July 18, 2018 Did the glove test. EGR command was zero and stayed at zero. The glove filled up and blew in about 20 seconds. Is that enough leak to cause my regen problem? Dealer is telling me it's injector cups. I checked the return for air. Nothing when i started the engine..10 sec got a burst of multiple large bubbles....no bubbles for 30 sec...then got a consistent small bubble every 5 sec or so. Thoughts? Quote Link to comment Share on other sites More sharing options...
jwmcgregor Posted July 18, 2018 Author Share Posted July 18, 2018 Checked it again and caught video...a couple bubbles when first started then nothing... Quote Link to comment Share on other sites More sharing options...
jwmcgregor Posted July 18, 2018 Author Share Posted July 18, 2018 Took the truck and the load of wheat that was behind it to the elevator with my TEXA hooked up. 97% dpf. A mile or so down the road i noticed the dosing valve was at 100%. Fuel supply psi to after treatment was low..like single didget. Temps did not rise. About 5 miles into the 14 mile trip the dosing valve was operating between 15 and 25% and the fuel psi to the after treatment was 64 psi...primary pump psi was 68 at the time. Temps came up to 900 and 1000 deg. The passive regen continued until I reached the check in. HEST light came on when I stoped. I continued the regen with the blue switch until i needed to move. Dumped the load scaled out and drove back with the dosing valve at 100% and single 1 psi on aftertreatment supply psi. Temps never got over 600 deg empty. Soot burned off to 78%...was at 80% when I reached they yard empty. Is it normal for the dosing valve to be wide open with no fuel psi....wondering if I have intermittent signal from the psi sender on the after treatment side or did it just make enough heat while loaded to successfully "burn"? Any thoughts? Quote Link to comment Share on other sites More sharing options...
turckster Posted July 19, 2018 Share Posted July 19, 2018 (edited) Usually if the egr valve is ok the glove will expand a little but not pop. You will have some air in the fuel return when you start up an engine but it should go away in about 5-10 min. When not doing a regen the dosing valve will be at 100% to purge air--to keep the 7th inj. tip clean. Being under a load may have helped the regen to build temp but if its not happening during a parked or forced regen there is an issue. Many things will affect a regen form one reason or another, but not building temp is usually either a dirty/poor spray pattern on a 7th injector (adaptive factor percentage should tell you condition of 7th inj.) or an egr valve flowing slightly all the time. It will also cause frequent regens. Another thing to consider, with egr failures we have seen over temps with egr coolers as well (plugged). It may not happen right then but it will happen soon. Best to check inlet and outlet on the egr cooler if/when replacing the egr valve. Also, check the egr diff. psi sensor ports for excessive soot. Edited July 19, 2018 by turckster Quote Link to comment Share on other sites More sharing options...
jwmcgregor Posted July 19, 2018 Author Share Posted July 19, 2018 Thanks so much turckster! I'm going to address the EGR valve as soon as I get a chance and possibly swap out the dosing module with one from a sister truck?? and see if things change. Could you explain "adaptptive factor percentage"...This tractor goes from 0% to 100% when doing a parked regen...when it was hot on the road with a load it ran 12% to 25% which is what the other 3 sister trucks do while parked.... Quote Link to comment Share on other sites More sharing options...
turckster Posted July 20, 2018 Share Posted July 20, 2018 Since you will be replacing the egr valve you should clean the 7th inj tip. We use Berrymans B-12 carb cleaner and a soft nylon brush but any quality carb cleaner should work. I wouldn't swap the dosing module. As a 7th inj. starts to get dirty its efficiency drops, that is it's adaptive factor (as the eecu measures it). When you replace or clean a 7th injector you need to reset the "adaptive factor" to tell the eecu to re calibrate to new. On Volvo/Mack software (PTT2) it's under the "aftertreatment diagnostics" tab, not sure on other software. During a regen the 7th inj. is at 100% to keep the tip clean(purging air), once the pre-dpf temp sensor reaches a certain temp then the 7th inj. starts to deliver fuel. Because the egr valve isn't closing all the way or leaking, it is cooling the exhaust temps enough to prevent proper temps. When going down the road under a load the engine was able to create enough heat to perform a partial regen. therefore the 7th inj. worked ok. Be careful when removing the egr valve mount bolts, they have a bad tendency to break off in the exh. manifold. Work them off slowly and use a lot of quality penetrating oil. When going back together use copper anti-seize on the bolt threads and under the bolt heads/spacers. Torque for the egr mount bolts is 35 ft/lbs. Good luck Quote Link to comment Share on other sites More sharing options...
jwmcgregor Posted July 21, 2018 Author Share Posted July 21, 2018 Thank you! Quote Link to comment Share on other sites More sharing options...
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