If a grill isn't cleaned periodically the grease build up will cause burners to clog and uneven heat distribution.
The grill will also flame up in areas where the are build ups of grease. Thus causing food to burn.
A secret I learned a long time ago about grilling is to use very low heat and cook longer.
Less propane is used, meat retains juices, cooks even and doesn't burn.
Also, best thing when grilling sausages is to boil them 1st to remove excess fat. The fat will wreak havoc on the grill.
Happy grilling!