No fuel - maybe

1999 Camaro V6 3800 series ll automatic 116k miles- gas gauge never did work. ( this may be important later)

rod knock so had mech replace engine with used one of 57k miles. (couldn't afford rebuilt) All seemed OK but did see oil pressure at stoplight wandered around 35-40 psi at idle about a day or so after getting it back from shop which worried me b/c the original engine WITH knock was always up around 60 psi even at idle. Mechanic said no big deal. Kept an eye on it and it runs 60 psi at cruise and now about 40-45psi at idle.

Anyway, about 4 days later it wouldn't start. Sounded very familiar to running out of gas but was pretty sure I had 1/3 tank and added 3 gallons just to be sure. No go.
Towed back to shop that did engine swap and he says fuel pump dead.
fuse is good and he claims relay is OK.

I pulled the pump and metered it out. It must be intermittent b/c sometimes I get continuity and sometimes not. Checked a new pump and there is continuity across pump motor so I should have it across mine but don't. Also float level resistance wiper is shot thats why the gas gauge not working.

Ok. check for voltage across grey and black feed for fuel pump with key on (not start) and no voltage. Checked battery and it's almost dead (9v and would nt take charge) so:

1. Installed new fuel filter (will need one anyway)
2. installed new battery
3 found a u-pullit fuel pump for $15 (compared to $400 Autozone and $600 dealer. I asked 3 times if we were talking about the same thing and they said yes $15 and it's gauranteed so not complaining. (if not there's another for $60 at another junk yard gauranteed). Will buy tomorrow.

Now I read that oil sending unit controls fuel pump. I know I have several issues going on at once.

1. Could the fluttering oil sending unit cause no voltage to the wires back to fuel pump?
2. Daughter ran out of gas several times months ago due to no gas gauge- could this have helped
burned out fuel pump?( I know immersion in gas keeps pump cool so we never kept trying to start engine when I knew it was out of gas until I could get fuel into the tank)
3. Don't know where to find fuel pump relay. I know it must be in one of the 2 boxes on drivers side fender well but not marked.
4. What position should key be in to check for power back to fuel pump before I install the new used one?
5. Does the relay override the oil sending unit at start?

Just shelled out plenty for engine. Out of money. Ready to drive this off the nearest cliff. Burned out on this vehicle.

Any help appreciated
Thanks

The FP relay is in bottom fuse box (underhood fuse box number 2). The PCM controls the relay- The wiring diagram shows fuel level and oil level sensors ARE indeed an input to PCM- so PCM may be deciding whether or not to activate FP relay based on low fuel- I have always suspected this- on this car- but have yet to prove it or to confirm it.

Those FP are a pain to change- have to drop rear axle to drop fuel tank...I'd be sure the FP is bad first. Does it run when you jumper out relay? Put a FP pressure gauge on it and jumper relay.

Fuel pump out in 15 minutes with pneumatic chisel. Will reclose trap door with sheet metal and rivets. Bought used pump. Put 12v from battery on and it runs as opposed to old one. (only ran it for a few seconds. And float resistor works too!)

Now have to splice in different connector. It was from a 2000 V6. Hoping PCM is sending juice to connector. I wonder if engine swap they didn't get some connectors tight and it worked loose. It did run for 4 days after all.

Will keep posted.
Thanks

Guess I got lucky. Fuse, relay, sending unit and computer all OK. Pump works fine. Fingers crossed. Bad battery added a couple hours to job. Confidence in this vehicle is down.

1. New motor
2. Bad fuel pump
3 Bad battery
4. Code 420 causing new cat converter install
5 new brakes
6. all new O2 sensors
7 new MAF sensor

All in span of 6 months . . . not good.