I've got a 93 F-250 with a N/A IDI manual with about 165k on the clock. It's recently developed a new noise after I replaced the fuel return assembly. Previously, my truck ran fine and had no white haze out of the tail pipe. I replaced the return assembly due to concerns I was getting some air intrusion. The assembly was the original one and the hoses were cracked at the ends. Having read around here a bit, I ordered the Delphi return kit and picked up the correct O-rings from McMaster. I also replaced the 3 olives while at it. Initially, I had some fuel leaking from the plastic fittings on the injectors but was able to get them to seal.

Now at idle it faintly hazes white out of the tail pipe and I have a shudder (misfire?) at about 1300 RPM. I also now hear a "rattle / clatter" when I rev it when it neutral. When I'm driving I can distinctly hear it when accelerating. Temp doesn't seem to effect the noise. Reading around some I see that injectors can cause noises like this and I'm wondering if something happened while I had the system open. I went around to each injector with a stethoscope while revving it but they all sound the same to me. I also went around the valve covers and listened with some heater hose to my ear. I don't hear anything odd from that area at idle.

At this point I'm scratching my head a bit and thought I'd get the advice of people more familiar with these engines. I see that around this many miles people recommend new injectors and pump but I find it odd that it suddenly started right after I worked on it.

I took some video if the noise


Thanks

 

I went out an loosened the injector lines one by one and tracked the issue down to the #1 injector. I'm going to try to pull it apart and see if I can find anything inside causing an issue.

 

I pulled the #1 injector and disassembled it. The needle didn't come out freely but I was able to get it out without damage. I found a small spot on the needle above the tip where the carbon had been cleaned off. So, I'm assuming something got in there and wasn't letting the injector close all the way. I cleaned it up and the needle moved freely in the bore and spun without issue. After reassembling the injector, I put it back in the truck. That fixed my issue and the truck is back to running like normal. I'll leave the post and videos up in the hopes it help someone else down the road.