Microplate readers (or ELISA reader in your term) usually work through absorbance, not through fluoroscence. The usual plate-reader that we use are all gives the result via passing a light through the plate and taking into consideration the amount of light that was absorbed in individual cells. Although Fluorscent plate readers are available, due to their high cost we (in our country) don't usually use them for this purpose (as per as I know) and thus our ELISA techniques are based on absorbance. So in order for the flurorometer to have a minimum chance to work you have to modify your ELISA accordingly. Next it depends upto the type of the Fluorometer. If it is a spectrofluorometer, I guess it may work. But instead if it is a filter fluorometer, I don't think it will work.