We had a 6.0 Powerstroke come into our shop last week that gave us fits. This is why it’s so hard sometimes for shops to get the diagnoses right instantly. The truck had been in a different shop for head gaskets and some other work. Afterwards, it never ran properly again. It would cut out and buck randomly after running for a while. They brought it to us to try to figure out after the original shop was out of ideas.

We went through and checked all the simple things first. The fuel pressure was way low. It is supposed to be 50 PSI and would easily drop into the thirties. Ah ha. We got it. Put a new fuel pump and upgraded regulator in it figuring the problem was fixed. Nope. It cured the low fuel pressure but it still would buck and cut out after running a little bit. So we next proceed to ruling out every sensor on the engine by unplugging them one by one. Nothing changes, but we did realize that the other shop left the throttle plate in the intake even though they deleted the egr. This can cause the bucking issue. Ah ha. We got it. Nope.

By the way, the truck is throwing absolutely no codes and passes all diagnostic tests on the scanner. So next we decide that it could be a faulty IPR valve since we have ruled out everything else and swap that out with a new one even though the one that was in there looked brand new. Nope. At this point since we are grasping at straws we decide to also swap the oil filter out since it is the NAPA style large cap that we have seen issue with before. When we do we realize the oil smells strongly of fuel. We had checked the oil level when it came in and it was on the full mark. Not it is way over full. By about two gallons. Oh boy.

Here is the thing, there is really no way for fuel to get in the oil on the 6.0 Powerstroke if it is running ok. Which this truck was. No smoke, missing, or anything out of the ordinary. Usually if an oring on the injector is leaking the truck will miss terribly and hydro lock. The only place that fuel can come from is the injectors though. So we decided to pull them all for inspection.

The culprit was that the injectors were not torqued properly. They were all very loose when we removed them. But oddly, this usually cuts the orings and lets fuel pour into the cylinders causing all sorts of smoke. The reason they were not was that the other shop had coated the bottom of the injectors in some sort of grease. I’m not sure why. I’m assuming this was sealing the lower portion of the injector from the cylinder and letting the fuel come up into the valve cover area and mix with the fuel.

We replaced all the orings on the injectors and torqued them in properly. The truck ran a lot stronger after that and the problem was gone. Unfortunately, we had to go through all these other steps to get to this solution. Hopefully this helps someone else who has a similar issue.