Idle problems for '82 300 TD

I have an idle problem that will rise and then drop to a lower RPM when cold. After the engine warms up, the problem is gone. What could be the most likely cause?

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

Most likely a fuel pressure issue

Either restriction with fuel coming from tank (clean tank filter screen and replace both filters), or air getting in to the fuel system overnight. Check all hoses and clamps replace at needed. Or you have a problem with your mechanical lift pump (mounted to the bottom of the injection pump. It could also be a problem with the injection pump itself but that is the last thing you want to worry about.

Fuel rack damper bolt

This is also symptomatic of a fatigued fuel rack damper bolt spring. I had the same problem with my 82 300TD. I had to feather the fuel pedal to get it started and the idle speed would fluctuate, especially when cold.