Its probably not your issue, but make sure the cap is all the way seated on the frame filter. I have seen several folks stop tightening it and the o-ring not be seated. If that is the case, then it will suck air. IF you changed the top filter and then changed the bottom, take the top back off, cycle the key quickly, and put it back in. One of the guys changed the top one, took the bottom one off and started talking on the phone. When he tried to crank, it would not start. Messed with it for an hour and finally took the top filter back out, It burped and we cycled the key to purge the air out of the line and it cranked after that. It should not have done it but it did.