Car dying when idling

I recently replaced the accelerator pump diaphragm on my 1920 Holley. I drove it for a while and it worked good, but the car was a little slower then it used to be. The next day, the car will start but will die shortly after when at idle and will only run when the car is being driven. Stopping at lights or stop signs causes the car to die abruptly. Is it related to the accelerator pump?