Interesting to hear of a problem with a 1.7IE- they are normally pretty reliable.
It sounds very similar to a problem I experienced with my 33P4 a couple of years ago. I don't know what your knowledge of fuel injection is so forgive me if this is a little basic.
With the Jetronic system (and most others) the fuel pump operates constantly and the pressure in the fuel rail (to the injectors) is controlled by a pressure regulator which sends excess fuel back to the tank.
This regulator maintains a constant pressure except under acceleration when change in manifold vacuum is used to increase enrichment. When you turn the vehicle off, the regulator should shut off the return line so that pressure is maintained within the system.
This is important because if pressure drops within the system, the fuel can vapourise in the lines and prevent restarting. Pressure drop can be caused by dirt or incorrect seating of the valve within the fuel pressure regulator.
This can be easily seen if you have access to a fuel injection gauge test set, as the pump is turned off the pressure will fall away. This can be fixed by replacing the valve but often the valve can be reseated by momentarily clamping the return line from the pressure regulator and then quickly releasing it, this can cause any dirt to blow out of the valve and reseat internally.
This solved the problem on my 33 which returned to starting fine after being left hot on 40 degree days! Be careful doing this if you are not familliar with fuel injection, if you are not careful you can overpressurise the system and rupture hoses and cause a fire- safest to do it with a test gauge hooked up to prevent excessive pressure.
Hope this helps