CP4 Injection Pump Failures
There are few redeeming factors regarding the design of the Bosch CP4 injection pump. For an in-depth, detailed review of the CP4 pump's shortcomings and causes of failures, see: CP4 injection pump failure causes. It is widely believed that domestic diesel fuels perform below the minimum performance standards required to properly lubricate the CP4 injection pump, resulting in premature wear and often catastrophic destruction.
A typical CP4 pump failure results in metal filings and fine metallic particles being distributed through the fuel system, ultimately clogging fuel injectors and lines. Such a failure requires an entirely new fuel system; fuel pump, injection pump, eight fuel injectors, and every line where fuel flows, in addition to removing and cleaning the fuel tank itself. CP4 pump failures are prevented by adding a supplemental fuel additive to every tank of fuel.
Excessive Fuel Dilution ("Making Oil")
Fuel dilution in the 6.7L Power Stroke is caused by the active regeneration component of the diesel particulate filter system. During active regeneration, fuel is injected into the exhaust stroke and is channeled through the exhaust system and into the DOC where an exothermic reaction occurs, raising the temperature of exhaust gases flowing through the DPF in order to burn off combustion material captured in the filter.
The fundamental problem with the post-injection method of introducing fuel into the exhaust stream is that raw fuel is bring transfered through the combustion chamber, where it has the propensity to stick to the cylinder walls. The motion of the piston then allows diesel fuel to pass behind the cylinder rings and enter the crankcase, contaminating the lube oil supply. Fuel dilution is worse and widely more common in vehicles that are driven in stop-and-go conditions or that idle frequently. Keeping the vehicle moving at highway speeds with minimal stops is the most effective means of reducing fuel dilution in 6.7L Power Stroke equipped vehicles.
SST Turbocharger Failures
Turbocharger failures have been common on 2011 and 2012 model year 6.7L Power Stroke equipped pickups. The weak link in the Honeywell DualBoost turbo during early production years seems to be the ceramic ball bearings. Reliability concerns with the turbocharger were eradicated with the introduction of steel ball bearings. A turbo failure on these model years is hard to miss, as an obnoxiously loud screeching sound is exhibited in addition to smoke being emitted out of the tailpipe due to burning engine oil. As the turbocharger design is relatively advanced, it's also quite expensive to replace.
NOx Sensor Failures
NOx sensor failures were extremely common on 2011 model year engines. Under certain conditions, engine power is reduced as a result of a faulty NOx sensor. Frequent sensor failures on a large scale prompted Ford to initiate Custom Satisfaction Program 12B33, in which technicians checked and replaced faulty sensors in addition to uploading an upgraded emission control strategy for the SCR system. The Customer Satisfaction Program expired April 30th, 2013.
Glow Plug Failures/Dropping
There have been multiple reports that the glow plug tip on early production 6.7L Power Strokes may break off into the engine, causing a catastrophic failure. These incidents were not widespread and there have not been enough cases to prompt a recall or any considerable concern in later production engines. The problem seems to be isolated to certain chassis cab models. Had Ford detected a problem with the glow plugs, a recall or service bulletin would have been likely in order to reduce the onset of expensive warranty claims.
EGT Sensor on "Ambulance Package" Chassis Cab Trucks
At least one faulty EGT sensor was identified on 2011 and 2012 model year F-350/F-450/F-550 trucks equipped with the "Ambulance Package". The emissions aftertreatment system on the 6.7L Power Stroke diesel features several EGT sensors. When one of these sensors fails, a vehicle may shut down while driving and/or fail to restart. Considerable controversy resulted as emergency vehicles were left stranded, prompting Ford recall 13S10 to replace the faulty sensor(s). Similar instances have been reported in pickup models, although these incidents appear much more isolated and have not contributed to widespread concern.