Hey guys, I though I would share this most recent repair with you all b/c of the complexity of the diagnosis and direction the repair went. I had a 2005 F550 w/6.0LPSD w/dump body on the back and 57K miles. Customer complained of fuel loss and stalling. The customers own personal truck mechanic brought me the truck after picking the truck upfrom another diesel shop and they diagnosed it as needing 8 injectors, fuel pump module and an FICM.
Symptoms: Truck starts perfect, idles for several hours with no problem, plenty of power but slightly less than 100%, no overheating, slight imbalance of power while idling, but no dead misfires. Engine would run mint for 1/2 mile under full acceleration and then lose power rapidly, seaming like each injector was cutting out 1 by 1. If the truck was driven causualy, it would go bout 2-3 miles before the same 1 by 1 injector drop out would occur under acceleration. The truck would start again after cycling key a few times and cranking over. There were many codes present for all 8 injectors, a few glow plugs, loss of signal for CKP sensor and a few other DTCs. I believed this to be from the many hands "playing" with the components and controls.
Diagnosis: Cleared the codes and drove it only to have a few injector codes and GP codes return. Additionally, if the cap on the secondary fuel filter or any joint in the fuel system were removed, a burst of pressure would spray out. More pressure then the max of 45psi that the system should ever see. Obviously, something was pressurizng the fuel system beyond the fuel pump. I tested a few other things and replaced the fuel filters only to find they were fine, but did so simply to satsify my suspicions. The one code that caught my attention was a performance code for inj #1, b/c the others were not performance codes, but resistance and so on. Using a temp gun, I checked that cyl #1 was infact not reaching the same temps the others were.
Repair: Replaced injector #1 finding no visible damage to the copper washer, injector seat, orings or the inj body. Reassembled and test drove. Truck ran great for a mile or so, but a misfire indicated on cyl # 5. Fuel loss and stalling ceased and did not occur after 10 miles of driving. R/R inj #5. Reassembled and test drove for another 5 miles. Truck ran like an SOB. Trouble was fixed.
I hope this will help others with the same problem. Apparently, if an injector fails, depending on the nature of the failure, the injector can allow compression to be introduced into the fuel supply backwards from the injector nozzle. This in turn overcomes the delivery pressure and starves the injectors of fuel. The most important features to keep in mind, are the extremely high pressure in the fuel system and the accompanying misfire. BE CAREFUL! The pressure in the fuel system overcame the check valves (did not damage them apparently). This was extremely dangerous b/c the burst out of the secondary fuel filter housing was like a water balloon popping w/less volume in the spray! This can catch you off guard espcially if your not wearing safety glasses (as you should while working w/any pressures).