Patrick_Hamann

If I bring it in today ill pull the filter and check it out and let you all know

Hey guys, Complaint is that this truck will lack power after 1-2 hours of driving on the highway, 65-70 mph. A little background on the truck, it is a Charter Communications bucket truck, has a utility bed and is LOADED down. The customer states that you have to hold WOT to try and maintain speed uphill on highway. 310,xxx miles on the clock. I test drove the vehicle while monitoring inlet restriction and fuel pump pressure at the outlet of the pump, Inlet restriction stayed at 7 in. hg the entire time, idle, or wot. Fuel pump pressure stayed solid at 62 PSI. According to history the fuel tank, pickup and pump were replaced for restriction from rust/delamination 60k miles ago. max boost is only 13 psi. My question is would it be possible that the 7 in. HG of restriction be a sign of delamination even though fuel pressure never drops? Any help appreciated. i drove the vehicle for roughly 1.5 hours and I could not fully verify the concern.

Ive heard this before on a 6.4 and the high pressure turbo was shot, bearings went out and the compressor wheel was making contact with the housing.

I have my fingers crossed hehe, still have to finish it up tomorrow

I made some progress today, only had about 1.5 hrs to work on it but I removed the turbo and disassembled. found no carbon coking or siezing, carbon was pretty light, unison ring looked good, very -slight- wear on it from the crank pin. went ahead and cleaned it all out per WSM, the shop manual says to put antisieze lube on the unison ring and on the housing (I went ahead and did this but I was always told not to do this by several people) so correct me if im wrong there. I went ahead and powered up the VGT actuator per PPT KA5. sure enough, the valve did not move, even at 100% duty cycle, repeated 10-100% on active command 5 times, finally, I tapped on it with a wrench the valve popped and moved. I cleaned the valve with PM-2 carb tune up cleaner per PPT AK7, tried again, then the valve would move each step. Im thinking this would explain my intermittent underboost and my surging,and it working after it warmed up BUT, I ordered a new VGT actuator and im reinstalling tomorrow and I will let you know how it goes

Thanks for the tip mchan, Just an update, Test drove the vehicle this morning, still lacked power, wouldnt build any boost. After it reached operating temp then it seemed like all the power came back and didnt underboost anymore, surging was still present, EGR pids would cycle between 6-100% VGTDC 32-42% under moderate load cruising. went ahead an ran pinpoint test KA. havent removed the VGT actuator yet to watch it move but I will tomorrow. Boost test and EGR test passed on IDS. The VVT test didnt look so good on the graph. It would overshoot each step by quite a bit. but still had the 7 steps. hotline seems to think the turbo is coked/siezed but I have a pretty hard time believing that since it only has 200 miles on the new turbo (this bus sits alot). Unfortunately no one in the shop has a known good VGT actuator to put it so I feel like the next step is going to be removing the actuator and cleaning it. Did notice that if I took active command of VGTDC# the surging would completly stop. I do appreciate the tips, im a new diesel tech and still learning the ropes. Thanks guys Keith, the whole turbo assembly was replaced

yes it is a cylical surge, comparable to 'trailer hitching' but im going to reinstall the EBP tomorrow and retest. If the VGT solenoid is bad would that show up on the VVT test on IDS/VMM?

Bus came in with a blown egr cooler. Diaged and replaced EGR cooler, Oil cooler. Found turbo completely siezed from coolant,worst turbo ive ever seen. replaced turbo assy, did not replace the VGT solenoid. vehicle came back a month later with a lack of power concern, wasnt building any boost, roughly 7 PSI MGP at WOT. found the catyltic converter plugged. replaced cat. Boost now around 19-20 PSI WOT. Watched a few pids, noticed that EBP_G will surge from 31-37 psi, also VGTDC# will also have the same 'sawtooth' pattern. ICP, ICP desired are solid at 3100 PSI wot, no pattern in graph. noticed that EGR pids do not move, Desired pid stays at 0. wont pull to redline, stays around 3000 rpm. Tested fuel system with diesel fuel flow tester at back of cyl. head. pass. 38 psi. no dtcs's present. Removed EBP sensor, found the tube partially plugged cleaned tube. do you guys think that the partially plugged EBP tube could cause this? any help greatly appreciated. it will surge basically anytime, hot or cold.