Originally Posted by
97Silvia
Hi all, Been having some real troubles with a 15 F550 6.7 Powerstroke- 85K Miles- Been working on this truck for a week now and unfortunately am stuck scratching my head and could use a little assistance or opinions- Ill provide some details here about the truck, And follow up with my general questions at the end-
Truck came in about a week ago, It showed several codes- P008A (Low fuel pressure low side), P0087 (Low Rail Pressure), and P0093 (Fuel system large leak). Went for some test drives and noticed the problem could be difficult to replicate- But it seems more likely to occur under increased load (Trailer, Hills), While operating temp is hot. Initially, I found a broken housing on the frame mounted low pressure pump as well as noticed it was growling pretty good, changed it out and it seemed to make a good improvement. Went to conduct more test drives and now it acts up far less often, however it still will randomly trip a P0093 which causes the truck to disable fueling and stall out as a safety feature to my understanding. Truck will crank back up and run after coming to a stop and shifting to park, Before replacing the low pressure pump it sometimes would take a lot of cranking however it has since been able to fire up pretty quickly after throwing the P0093, I havent seen a P008A or P0087 code since the pump was changed.
Ive searched through the fuel system quite meticulously, Bypassed the tank and ran the low pressure pump feed/return to a fuel cell on the back and it seemed to make a great improvement, Hammered it around on a test drive for 45 minutes with a trailer on, No stalls and figured perhaps it was solved. Unfortunately went to confirm it with another test the day after and received the same P0093 while accelerating up towards 80 Km/h, The truck had been reaching and maintaining 110Km/h without issue for well over 30 minutes prior on the same test run so I'm quite stumped as to what variable could be changing. I suspected possible air intrusion however I cant figure anywhere else that could happen without obvious visible signs. The truck had been elsewhere for diagnostics beforehand and nearly all the high pressure side of the system has been replaced already. The injectors and fuel rails are original, But show no signs of issue, Did a key on eng off check for leakage at injector return line, and still rather low mile units) The Low pressure switch/Temp sensor, HPFP and VCV, Pressure sensor and regulator in rail are all new. Which I suppose doesn't necessarily mean good, However its made me hesitant to suspect problems with them. The frame filter and engine bay filter have of course been replaced as well. I try to monitor my live data and get the symptom to act up, Unfortunately I have access to an Autel instead of IDS program. However monitoring what parameters I can, Most of it seems to check out well.
The rail pressure actual Vs commanded stay in a very tight range (until the single freeze frame when the DTC sets and the Frame pump is commanded off), and has no problem reaching a full 29K PSI. I can monitor PIDS for "Fuel Volume Control Valve 0-100%, Fuel Volume Control Valve current measured" as well as "Fuel pressure control valve 0-100%, Fuel pressure control valve current measured"- I have a decent understanding of where these components are and what their function is supposed to be- However I cant help but feel like this new VCV is a bit suspect. Both PIDS for current measured lists a nominal parameter of 0-3A on my Autel. The (rail) pressure control valve seems to always stay within this and the % and current both seem to move in a pattern together. However my Volume control valve current will read around 1-2 amps, Then my reader will sometimes say the measured value is 500-900 which seems implausible. When the VCV current takes a dramatic swing like this, The VCV % parameter only changes slightly and they dont seem to have much corelation with eachother. I did notice I seem to only encounter these types of implausible data figures while my engine load parameter reads above ~45%. As soon as I start taking the pedal out, It drops back to a normal ~1.5ish Reading. I dont necessarily notice any dramatic changes with other parameters when this is occurring (Rail pressure, Ect seems alright) and on the occasions I see this I wouldnt ahve any clues anything strange is happening aside from looking at and reading the scanner. However I have had the truck stall on the P0093 while watching this data and it has only occured while this data is out to lunch.. May be just a coincidence.
Anyhow, in conclusion- I have 2 questions here. I dont see any actual problem with the systems, Im concerned the truck sees some strange data for a quick moment and trips this code. Is it possible I can go to tune this truck and disable the P0093 code? With the code disabled, will the truck not be forced into a stall ("Reduced Power") in this condition? Or will it just mean Ill have the same symptoms and just no trouble code to observe? I understand this is a band-aid type fix as the truck is acting this way for a reason.. However im feeling pretty confident it doesn't have any detrimental problems and would likely continue driving fine if the PCM wasnt seeing an issue and disabling the pump.
Is anyone familiar with these data Pids on this 6.7 Chassis? Does it seem like I might have a problem with the VCV or am I just chasing a ghost with that idea? Any other suggestions would be very appreciated. I have some data saved in screenshots and am more than happy to share more details, answer questions, or run tests that may help reach a solution on this. I think this is my first post on this forum however ive been watching and learning here for a while now and am hopeful im looking in the right place of knowledgeable people. My tuning knowledge is still limited and growing however I have done some GM AFM disable tunes and am curious if I can just check this code out the way I would on one of those.. Seems too easy but id be happy to hear that could work. Lol.
Thanks in advance!
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