This is for all the posts I have read where people have complained of poor performance and have tried replacing injectors, compression tests, rebuilding cylinder heads, adjusting valves, looking for clogged Alda lines....Please check your FUEL PUMP. Today's Low Sulfur fuels and sometimes inconsistent fuel quality can do a number on your Fuel Pump!!!

I figured my 85 300D was dead in May after I ran it down to .5 quarts of oil--everyone said the engine was dead and I had to double pump the gas pedal to get power. Even a reputable indy said the engine was so loud that it must have been held together by the steel filings and debris from the loss of oil incident and that it might self destruct any day and throw a rod through the block..
I wentt out and bought a "new" 87 300D and fixed it up I took the 85 300D for one last farewell run because it was the only one I had with AC on it--on a 700 mile trip that took me through West Virginia and up and down some pretty tough mountains--and I when i got back I noted two things: I hadn't lost one drop of oil, and the car never gave me trouble on the mountains, as long as I double pumped the gas, and it still did 90 and at times was very quiet..
I got curious about the 85 300D last week and pulled my pan and found no engine debris. I did an oil analysis and it was okay. No scrap metal indicating engine damage.
I pulled my Pump and sent it in for rebuild.
Today I got my answer from the rebuilder: The Alda was badly leaking, and two of the cylinders were really caked and solidly carboned and the remaining three needed new parts--the pump was junk---the rebuilder mentioned tha today's Low Sulfur fuels (no lubrication) and inconsistent fuel quality are the Death of many pumps he sees..suddenly all those posts where people have complained of poor performance and have tried replacing injectors, compression tests, rebuilding cylinder heads, adjusting valves, looking for clogged Alda lines came to mind--so all I can add is check your PUMP