Hey there,
I bought my first diesel, a 2003 F350 King Ranch with the 6.0 . Have had it for a month and been slowly doing maintenence when I can. After I replaced the alternator, about a week later, I'm getting code p0261(cylinder 1 injector circuit low). The cylinder dropped out very suddenly while driving home after running errands. I had already gone 40-50 miles that day with half a dozen restarts and never noticed the classic shudder/shimmy.
FICM was replaced by someone prior to me and is giving 48.3V but I cannot run a successful buzz test. All this leads me to believe I screwed up the electrical connector at cylinder 1 right under the alternator, but it doest seem damaged, it wiggles a little but doesnt seem "loose" or fall into the head type thing. I'm out of ideas on how to diagnose my problem.
I know there are some things I can do to help the injectors, like I want to put in a blue spring kit, new fuel filters, and I'm probably due for an oil change, but the failure was pretty quick to be those things, I would think... Also the truck was throwing a code for glow plug circuit on cylinder 4 and thats how I found the bad alternator, but this cleared as soon as my starting voltage was correct. Weird thing is it threw the code again on my first cold start this morning for the first time since I replaced the alternator, but then did not repeat as I restarted the car for several tests. I have no idea what this means.
Ideas are appreciated,
Argus

 

What voltage are you getting with the new alternator?
Check you tube for some Diesel tech ron videos on diagnostics for glow plugs. Pretty easy tests that you can do to see if they are in spec or not.

 

Can be any number of (multiple / chained) issues --- start by confirming grounds, doing housekeeping under the hood:

 

Thanks guys,
I appreciate the help but I am way beyond those ideas. Maybe I gave too much info... I think there is a broken connection between the FICM and the Injector. I have decided that a full replacement of the wire harness and a New FICM would guarantee a fix but that is a lot of work if I can find the one bad connection. But my chiltons manual electrical diagrams look like they were drawn by a colorblind child so as of now I'm just going to keep chasing wire till I find something broke or disconnected. And the alternator is giving 14.0-14.2V as expected.
Argus,
*update* I was mistaken and it has the original FICM so I'm probably replacing it no matter what

 

You could try swapping injectors around. See if the misfire stays at 1 or moves to a new location. Seems you would want to investigate a repeat glow plug code. There are some easy tests that can check if they are in spec.

 

You can use a multi-meter to check the #1 connector for shorts to ground and the injector's resistance to confirm it's in spec. My diagnosis software says P0261 is usually fixed by replacing the FICM or the injector. Less frequently the harness and fuel filters.

 

I think you hit it on the head. I went to pull the FICM so I didnt have to return for the core fee(extra 1.5hr travel) and the wire harness furthest in the back of the FICM had never been locked in. Not even sure how it ever functioned, as somebody must have bumped it when installing the obviously new air intake. Once I snapped it back in it threw every past code and a few extras, but upon a full reset and restart the thing performed better than it ever has for me. Will drive it to scrub the p1000 code, but at least its nice to drive now. I appreciate the help guys! Another victory for the boards.
Argus

 

Even a Bonehead's broken clock is right twice a day. Congrats!