2001 2500HD "misfire cyl 7" help
 

First off it a 2001 2500HD 6.0L w/345,678 miles. About 2 weeks ago I noticed my truck starting to spit and sputter so I looked around and found out that my "secondary" fill tube (the small overfill @ at gas cap area) was loose and hanging down and had water and dirt getting in it so I changed filter (very dirty and "muddy") and ran heet and techron thru 2 tanks. It somewhat got better then started getting worse again. Codes said right and left banks "lean" and numerous misfires. Changed plugs and ran seafoam thru it. Codes now only read misfire cyl 7. It will start right up when cold but after running awhile and shut off it takes for ever to start (after warm-up). Sometimes runs ok but under a load the check engine light always flashes. I moved the coil to another location and the code did not follow it. I did clear codes after re-location and it came back cyl 7 misfire. Sorry the post is so long but I wanted to give as much info as possible. PLEASE HELP. Thanks Jon :confused: :( :eek:

B.T.W. I did a fuel pressure check and I had 55 lbs at key on, 44 while running and when I put under rpm's it rose a little but after key shut off it drops rapidly. The pump was changed out last 9 months and I took the Fuel pressure regulator to the parts store and had it checked under vac and it held ????

Sounds like #7 injector is filled with crap. It's the first one in line on the receiving end of fuel. Check and see if the inlet to that injector is stopped up.

Thanks for you input and I will check that as soos as I can. When I pull the rails should or will I have to replace o-rings. probably should huh. Jon

Yeah I would replace them. If you end up replacing an injector, it should come with new o-rings. I found a similar stuation on a newer, 2006 I think, cutaway van I was working on. Changed plug, swapped coil, just like you did. Pulled the injectors and sho nuff, #7 was packed with crud and #5 was getting there. Seems GM saw fit to eliminate the fuel filter somewhere around that year. Ended up replacing the fuel tank as well. Hopefully your repair won't be quite as extensive.