Boom!!! no fuel......

I replaced my whole front end using the used HB that came with the car when bought. I got it all back together and drove it for weeks and started to enjoy it. Well, I went out the other day and tried to start it up and it chugged like it wanted to start and then I put the peddle to the floor to clear out the injectors. The very next time I tried to start it there was a huge boom that jarred the car even. I popped the hood and checked the usual culprit and the HB was on tight, lined up, and no chunks on the ground... I had my girlfriend crank the car while I pressed the check valve on the fuel rail....no fuel? I checked the shut off switch, it clicked when I pressed it. Is that bad? After I clicked it I tried to start it up, nothing. It still cranks and does not try to start. I did notice the last time I drove it the RPM gauge was bouncing around crazily? Any ideas? Also, at the same time the coolant gauge went to zero? I also checked oil, still perfectly clean? The boom came from the rear.

your car backfired from an ignition related failure and tripped the inertia switch in the trunk

dis module or cam sensor, replace them both and the crank sensor while your at it.

/end thread

Is it now getting fuel at the rail? Is the upshift light on while cranking?

An erratic tach when driving is a sign of a bad cam sensor, but it would start with a bad one. As for your coolant gauge, check the sender wire on the thermostat housing I bet it fell off.