It's possible that the vacuum part of the fuel pump has a broken diaphragm and is causing a vacuum leak and engine backfire. I would test to be sure it's OK.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.