very weird

I have a 90 Cavalier with a 2.2 engine. We stripped the car this past thursday and started welding in a roll cage on friday. Friday nite we installed the battery, computer and a fuel injector and started the car and it ran fine. Disconnected the battery and the car sat until 4pm Saturday while we was putting in the rest of the roll cage. When we went to start the car it would not start and the only thing we cut the wires on was the electric fan. We bought a new injector and the car still wont start. Does anyone have any suggestions or had the same problem. Would really like to get it running as I know it will be fast on the track. Thanks.

The wire harness is likely melted where you heated it by welding, possibly from the first welding session. The fact that it started doesn't prove that the damage wasn't already done. Do you have fuel pressure to the injector? Do you have spark to the spark plug?

The wire harness is likely melted where you heated it by welding, possibly from the first welding session. The fact that it started doesn't prove that the damage wasn't already done. Do you have fuel pressure to the injector? Do you have spark to the spark plug? I have great fuel pressure and plenty of spark. It will try to fire off for a few seconds with starting fluid and when I pull the injector some fuel will drain into the carb and start for a second. The injector is not being told to open and shoot fuel. We read out the wires to the injector and throttle sensor and it checked good. Is there a chance the ecm got fried even though the battery was disconnected.