this bus was a tow in driver said it started heard loud popand it died i got it in had no fuel pressure put a low pressure pump in it now it starts up then stalls out in bout 2 sec then i have to pump the primer pump it will start again then stall now sometimes when it cranks it kinda locks up for a second then turns so i would think maybe its a stuck injector o and the driver said when he heard the pop it started smokin real bad but how would i check for a stuck open injector