My son is getting his '89 Fox body Mustang running after sitting idle for about 18 months, heads off for most of that time. Back together he put ~3 gallons of new gas in it only to find that the fuel pump's bad. We dropped the tank and it is nearly full (gauge is inop, too), about 12 gallons which is now about 1/4 new and 3/4 18 months old.

Would you drain the mix of gas out or install the new pump and run it?? Going to happen this morning, one way or another...he's gone to pick up the new pump now.