How is the gas pressure? Black iron pipe that is used for house gas lines is sometimes used for underground gas lines and these are notorious for rusting rather quickly. Even galvanized pipe can corrode depending on the soil chemistry. When we bought our house, I tried to run our heater, and it just wouldn't start. I called a pool guy out and he first thought it might be a regulator or igniter issue. After about an hour of playing around with this, he tested the pressure and found it to be very weak. It turned out that the gas line was pretty much corroded through. This was confirmed by a faint odor of gas in a couple of places in the yard where the line was run. We had to re-do the line. I called in a plumber and they quoted me $9200! I literally laughed in his face thinking I could do the line myself for much cheaper. I hired a couple of guys to dig a trench, and then talked to our local building inspector. He requested sch. 80 PVC, but I soon found out that gas lines need to be done with yellow PE pipe, and this generally requires special plate welders. So, I called around and found a plumber who would do the line with welded PE pipe, including the appropriate PE to coated iron risers for $1200. This was very reasonable for a 150' run of 1 1/2 inch line with a T off to the BBQ island. So, for about 1/4 of the cost of the original quote, the line was done. The inspector did a pressure test and all was good and up to code.
Obviously, I wasn't happy when I learned that the gas line had to be replaced, but it's good to know that it is much safer now and likely to last much longer. You should definitely make sure to have the gas pressure tested.