Sensor on crankshaft ?

Please can someone help me out with a work around for my problem if it's possible. I have an intermittent fault on my crankshaft sensor which has been comfirmed by both the R.A.C. rescue and a Fiat technician. When the injector light is showing and I switch off the engine then it will not allow me to restart the car. I have been using booster pack to turn the engine over and after maybe 7 or 8 turns it may then suddenly clear the fault and allow me to start. Any Ideas apart from paying the asking price of approx £600 - £800 to fix ??