Ford Repair: mercury topas 1985 - deisel, gasoline engines, accelator

Question
QUESTION: I have changed the fuel filter. the car is still difficult to start and stay running.Do you have any suggestion to this problem?
Thank you!
ANSWER: Donna, could you give me some more detail about what the car does?  Does it backfire?  Does it just die?

---------- FOLLOW-UP ----------

QUESTION: no it didn't back fire.
at the beginning..It takes a long time to start up. It is as though thier isn't enough power to turn it on ..sounds almost like a dead battery....after the car starts to run I need to pump the accelator to keep it going..it slowly peters out even though I continue to pump the accelertor... and quits.
before the last start up it did blow out dark smoke from the exhaust.

Answer
Donna, how long has it been since you gave this car a tune up?  Diesel engines are not like gasoline engines, insomuch that you cannot turn the key and drive them for 100,000 miles and never do any maintenance.  Another downside to a diesel, is that the maintenance costs more.  The very first thing I would do is give it a tune up; glow plugs, wires, air filter, etc.  Maybe a glow plug controller as a last option.  Try this and let me know how it turns out,    Jason