Rough Starting Question

[psaboic]

Ok folks, I am having an issue that is starting to stump me….. rough starting first thing in the morning regardless of cold or warm weather. About a month ago I noticed the 300D suddenly starting rough, and when I mean rough I mean once the glow plug light goes out it will crank and fire within about a second after turning the key but then it runs like it has air in the system or is missing on a couple cylinders. It will knock kind of hard and stumble for about 3-5 seconds with noticeable medium gray smoke out the back then it will suddenly smooth out and will rev and idles fine and purrs like a kitten. It runs like a scared dog on the open road and idles smoothly when stopping. Warm starts are not an issue at all, just turn the key , and bang…. away she goes nice and smooth. It only seems to start rough after it has cooled way down i.e. sat overnight.

So far, I have tried fresh fuel, checked and adjusted the valves, done a diesel purge, changed the fuel filters, checked and tightened all fuel line fittings, and checked the lines at the injectors but it still starts roughly in the morning.

As far as the glow plug system, here is what I have done. I pulled all 5 glow plugs and bench checked them with a jump box. They all glow cherry red at the tip within about 3 seconds of voltage being applied. Next I metered out the wires from the glow plug relay connector to each plug and all the wires are fine (no opens or shorts). I put the glow plugs back in, hooked them up and checked them for resistance from the glow plug relay connector to the plug connector, and all of them read between .04 and .06 ohms…..so that seems ok. Lastly I checked for 12 volts at both sides of the glow plug relay strip fuse and that is ok, so I turned on the key and each glow plug is getting 12.5 or so volts until the relay clicks off……in a nutshell, the glow plug system seems to be functioning properly.

So why would it suddenly start rough when cold, but then run better than ever on the open road? The injector nozzles were professionally re-done about 5000 miles ago and they have been working fine. I suppose I could re-tighten the lines at the IP and/or see if an injector is loose, but wouldn’t that cause it to run rough all the time, not for just 3-5 seconds first thing?
Any suggestions greatly appreciated