means carried by at least one of {TAIL ~ the check} and the injector body for equalizing pressures acting on the first and second end portions of {HEAD ~ the check} such that axial forces acting on the check during movement between the sealing and open positions are substantially balanced 
means carried by at least one of { TAIL ~ the check } and the injector body for equalizing pressures acting on the first and second end portions of { HEAD ~ the check } such that axial forces acting on the check during movement between the sealing and open positions are substantially balanced
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH