74 260Z won't start. HELP

[srezzo]

So I ran seafoam treatment (1/3 in crank, 1/3 in gas tank, 1/3 through vacuum line) and afterwards car was difficult to start, but I was able to start it each time. After I would get it started it ran very strong after 2500 RPM, but sputtered below. I've since changed oil (as part of sea foam treatment), spark plugs, wires, rotor, distributor cap. I've also cleaned off contacts for the distributor and ignitor. The last few nights the car wouldn't start at all. Today when I went to start it I heard a POP (backfire?) and some smoke (very little) was coming out of the air cleaner box. I noticed one of the carbs was low on fluid so I topped it off with ATF. I may have damaged the starter trying to start it because it seems to be slower after cranking for a few seconds. I havn't tried spraying starter fluid in the carbs yet, but I plan to buy some tomorrow to try it. Battery voltage reads 12.5V. Any ideas on what the problem is? ANY???

Thanks,

Sari

[Mn_Z_Man]

You may have knocked loose some crud in your fuel system, that is now stuck somewhere it shouldn't be. Start with the fuel filter, should be easy. If that works, great, if not I would suggest a complete fuel system check from the tank to the carbs, including your pickup line, return line, electronic fuel pump, manual fuel pump, filter screens on the carbs, and float and needle valve assembly.

Also confirm your spark just to make sure its not your coil or something and the timing with the Seafoam is a coincidence.

Eric

[SteveJ]

Spark, gas, timing, compression. (We'll assume you don't have anything blocking air flow or exhaust flow.) All four have to be there. Double check your firing order. (Remember that some guides give it going CCW, and the older copies of the Haynes manual are wrong.) Make sure you have a spark. (I like inline spark checkers.) Make sure you have gas flowing into the carbs. We'll assume you don't have problems with compression for now.