2010 F-750 6.7 ISB cummins fuel issue

2vkiller · March 4, 2014

I have a strange issue with this cummins. The complaint I have is lacks power on hard accel. Code I have is 0559

I've noticed that the commanded fuel pressure when WOT is around 23000psi and actual is 13500psi. If I cycle the key off to on the fuel pressure is fine until i go WOT then the pressure drops again. Cycle the key off to on, it's fine. Problem only occurs when I go WOT. Any help is greatly appreciated. Thanks

Chris

66glide · March 5, 2014

I have a strange issue with this cummins. The complaint I have is lacks power on hard accel. Code I have is 0559

I've noticed that the commanded fuel pressure when WOT is around 23000psi and actual is 13500psi. If I cycle the key off to on the fuel pressure is fine until i go WOT then the pressure drops again. Cycle the key off to on, it's fine. Problem only occurs when I go WOT. Any help is greatly appreciated. Thanks

Chris

The first thing to check is the fuel filter. Next is the low side (supply) pressure.

2vkiller · March 5, 2014

Filters have been replaced

66glide · March 5, 2014

Do you have service info on checking injector return flow? If this is the same 6.7 used in the new dodge pickups, I can look up diagnostic info @ work tomorrow.

dieseldoc · March 22, 2014

559 faults suck to troubleshoot because they are very hard to create the conditions they happen and still be able to troubleshoot. I am going to venture a guess at the pressure relief valve in the rail, based on your symptoms. I dont remember for sure off hand on the ISB but on the ISX this valve is a two stage valve that once tripped will seat to a first stage after the pressure drops which will let the engine run but not at full power, it than will seat fully once the fuel pressure is lost at key off. It will be stated for sure how this valve works in the theory of operation section of the service manual, or possibly in the description of the system when you search the fault code in quickserve online. I have found though on the older common rail engines once this valve is unseated a couple times it is much more susceptible to opening agian. Do you guys use EDS(expert diagnostic system) for troubleshooting or are you lucky enough to not have to deal with this stupid system? Another common place we see high pressure leaks is the connector tube nuts. The high pressure connector retaining nuts have a tendency of loosening up with heat cycles or technicians not installing/torquing them correctly during service. I had an ISL in a truck one time that the only time I could get it to act up was flaming hot after 20 minutes on the chassis dyno and it turned out to be a loose high pressure connector nut, it barely moved when I put the torque wrench on it.