1984 300D lousy mileage after valve adjustment

I recently changed the glow plugs and reamed out the carbon on my 1984 300D with 129,000 miles on it. At this time, I also did a valve adjustment as I was told all of this would help with hard starting in the winter. Well, it has helped and the car has more power also. The valves were very tight and I had never adjusted them over my 15 years of ownership. Anyway, now my fuel mileage seems to have gone way down. I used to get around 22-24 with daily driving and around 28-30 on the highway. On a recent trip, I was getting 20 MPG on the highway. Any ideas as to why?
FYI, I also put in a lower radiator hose block heater but have not had to use it since the valve adjustment
Thanks

Forums

Diesel Engine Specific Aid

Chassis Model Number

W123

Look for something loose or out of place

Recommend you go back over your work and make sure all lines and hoses were connected properly and in the correct positions after you replaced the valve cover. Pay particular attention to the ALDA clear plastic line running over to the top of the injection pump. If everything looks ok consider rechecking valve clearances. There is also the possibility it may not even be related. Have you done a diesel purge? How old are your injectors?

poor mileage after valve adjustment

Haven't done a purge in over a year. Injectors are original. The plastic line going to the "ALDA" has not been attached since I have owned the car. (15 years). I don't even know what it does. There is some sort of banjo fitting there but no line and I do not know where the other end of the line weould go. Any ideas about that?
Again, this just started suddenly after the glow plugs and valve adjustment.
Thanks

Things to check

There are a number of things that could be causing your problems with may or may not be related to the recent work you did. But I would start by redoing your valve adjustment. In 15 years you could have had some carbon build up on the valve seats due. Adjusting the valves could have upset that carbon. I would start there. Then check your timing chain for stretch while you are at it and you definitely want to reconnect the ALDA. That can really throw off your fuel mixture. Timing and ALDA are covered in my manual, "Diesel Performance Tuning and Repair." I would also recommend you install new Monark injector nozzles. I suspect your injector tips are worn out...