Getting the lighter fluid taste out of burgers, after the fact
Make sure you don't squirt the fluid all over the grill.  Keep it on the charcoal.
If you have to apply more fluid after you've lit it, you're doing it wrong.  Douse the charcoal then wait a few minutes for it to soak in.  This is a common mistake.  People often pour on the fluid and immediately light it.  It then burns away before the charcoal can ignite and they have to try again.  You end up putting more fluid into the grill than is necessary. 
Let it burn long enough to burn away all the lighter fluid.  It sounds like you aren't letting the charcoal burn long enough before putting the burgers on the grill.