Volvo Repair: Starting problems, fuse holder, new spark

Question
I have an old 1986 Volvo GL240.  The car was given to me at a time when I couldn't afford a car, and I still am not able to afford a car so I am trying to keep this car running.  A few weeks ago I took my car to a mechanic and told him of my car not running well and using $50 a week in gas.  When I stepped on the gas pedal it did not increase the speed of the car.  He said he cleaned the fuel injectors, put in new spark plugs, and changed the air filter.  It did seem to run better.  Then I went to the store, and the car would not start.  The motor turned over, but I could not keep it going.  My son-in-law has recleaned the fuel injectors, changed the rotor cap and plug, but to no avail. It backfires. What else can he do?  We do not have the manual that came with the car. At one time he took the air filter off and it started, but not for very long.  What can he do next?  Rose

Answer
IF THERE IS SPARK AND FUEL WHEN IT DOES NOT START THEN TRY DISCONNECTING THE AIRMASS METER AND SEE IF IT WILL START.IF NO FUEL I WOULD CHECK THE FUSES FOR CORROSION ALSO CHECK THE FUSE NEAR THE BATTERY FOR BEING DIRTY OR CORRODED IF IT IS REPLACE THE FUSE AND THE FUSE HOLDER.