80 300SD hard start with warm engine

I have been having intermittent hard starting with the engine warmed up. The problem only happens after the engine has warmed up to 80-90 C. The car has new glow plugs decent compression (300+ average)and starts right away when it's cold (below freezing).
The car always starts eventually but I have to crank for awhile 10-30 seconds. Same problem when running on diesel or veg and with oil just changed or ready to be changed. I don't think that I'm getting air in the lines and again it's intermittent so sometimes it starts right up when warm?

Forums

Diesel Engine Specific Aid

Chassis Model Number

W116

How long does it sit?

How long do you let the engine sit before restart? Or does that not matter?

Hard start with warm engine 1980 300SD

It doesn't seem to matter (usually 10 minutes or less). If it's long enough for the engine to cool down some then it starts fine. Car is 1980 300SD.

Suspect vacuum shutoff valve not fully releasing

Try doing this the next time it will not start hot. Immediately get out of the car and pull the vacuum line off the shut off valve at back of injection pump. Listen for any hissing sound when you pull the line. If the engine will immediately start you have found the problem. Most often this happens when the two vacuum lines to the ignition switch get reversed or the vacuum lines are full of oil. This prevents the vacuum from bleeding off quickly so when you go to restart, the valve is still cutting off the fuel in the injection pump. Report back your findings.