darcet

i am experiencing intermittent hard starting problems. they only occur once or less a week, when car is fully warmed up. engine turns over, but fails to start. eventually i can get it started by pumping gas vigorously. check engine light then comes on with camshaft position sensor error code. have had local garage turn off light, but a week later it happens again. 96 impreza 2.2. anyone have ideas? thanx