Hi Sorry to hear about that.
May I have the full model number so I can assist you properly?
product-rangemaster 6237 RMSTR 110 GAS SERIAL NR-6237120007
When you say it lights, how does the flame look, check it against the other oven and please let me know.
when it lights its the same as the other one,but wont flame up after a minute as the other does
Do you mean only the igniter glows?
Or is there an actual flame, but its weak, this is important for me to know to be sure of the problem, please check this carefully for me:-)