1983 300SD. Could not start the car after is stood for awhile. I needed glow plugs but that was not the problem. I knew I had an air leak but could not find it. I finally tried everthing and as a last resort tightened the fuel filter down real tight. That did it. No more starting problems. I cannot believe that the filter was the problem. Must have loosened up over time. I will never take anything for granted anymore. Thank you for all of the help. Dennis