Check battery voltage, ignition distributor, spark plugs, ignition coil, ignition timing, etc.
If engine still does not start or starts only poorly after the electrical test, check for mechanical problems: Compression, basic adjustment of valves and engine oil pressure.
Check the fuel pressure. Is the fuel pressure correct?
Does the fuel pressure drop again after the end of the starting process?
Test the fuel-pump contact in the air-flow meter: remove the upper section of the air filter. Detach the plug from the air-flow meter and connect the ohmmeter to the terminals 36 and 39 at the air-flow meter. Press the air-flow meter flap open slightly by hand. The resistance must change from infinite to zero.
Test the start valve for leaks. In order to do this, clamp the fuel intake line closed with a clip. Does the engine then start when cranked?