presumably fuel delivery problem

[Metric Killerz]

hey guys, so i have had this problem since the day i bought my 77 280z, and nobody has been able to help me fix it.the problem: when it first started it would sputter and backfire at about 3000 rpm and get worse as i drove it. as time went on the problem got increasingly worse and became kinda undrivable. I found started investigating and found that the fuel pump would pulse and shut off then return "repeat". this would obviously  cause the engine to starve for fuel and sputter or stop firing all together. well i bought a brand new "presumably a real walbro 255 fuel pump" and replaced the stock fuel pump with the walbro. the z ran amazing for about a month and a half. then started sputtering, backfiring,dying, just like before. at a glance it seems the fuel pump went out again but i find it hard to believe that it would just burn up and die in a month, although i have ran under a half tank about the entire time its been installed, but i didn't think it mattered much on a external pump.  it has to be something electrical,fuel pump, afm, tps,realy, something along those lines. As of now the 280z is litraly un-derivable. it will start and run great for about 3 seconds then starts acting up, i can drive it for about 50 feet then it gets so bad to the point were the pump is barely functioning and cant touch the throttle  without it dying, it eventually just dies. im at a loss here guys, this is my baby and would love to drive her on the road once more. help or opinions would be greatly appreciated  

 

additional  -info: when i turn the key too acc the pump comes on and stays on. "i don't think this is normal" 

                 - the afm that is on the car right now  might be from a zx, the owner gave me a box of parts and there was a was looks to be a zx n/a afm, i know that some people do the zx afm conversion. i also know that the early 77 280z had a fuel pump cut off switch in the afm's and the later ones did not and it was run from the oil pressure sensor. from what i can see the OPS operates just find and when it is unplugged it does not in anyway effect the pump or running status of the z. 

                 - the only thing on the car that i know does not work properly is the temp sensor. but i know that thats the reason its making the car run lean,if that was the issue that doesn't enplane why it ran great with a brand new pump.  

Edited March 1, 2013 by Metric Killerz