350SDL ROUGH IDLE IMMEDIATELY AFTER START

Anytime the car sets for a number of hours (overnight) it starts normally, then after about two seconds it runs rough for about 3-5 minutes, then smooths out to normal. First thought was that air was getting into the fuel system but we have eliminated that through substitution of a hand pump and pumping fuel through the system prior to starting. When it begins getting rough after a second or two after starting it, the engine will sometimes die because of the "missing" effect. During the missing, it runs much like when one changes filters and the air has not completely been eliminated.

On another 350SDL with the same problem we went to the extent of replacing the injection pump and the fuel feed pump - this did not solve the problem.

Please help.

Thanks

[Edited by rbdrost on 07-18-2001 at 06:51 AM]

You might have the compression checked with warm engine & then allowed to cool down overnight and checked cold. Many times this engine will have compression problems.

350SDL rough idle
 

Sounds like a reasonable test and it is one that we have made - compression was OK. This was also pretty much eliminated as a cause because when it starts, is runs smoothly for a few seconds - after that is when is goes to running rough for a period of a couple of minutes. Is there any pump adjustment? Noticed that there is an adjustable bolt on the back of the pump - just above the electrical connection. What does the electrical connection control? When it is running rough it changes slightly when I disconnet the electrical plug.

Help - Bob