The tank flow of your Eljer toilet is determined by the amount of water within the tank. The less water in the tank, the less flushing power your toilet will have and vice-versa. To adjust your toilets water flow, the float connected to the fill valve will have to be adjusted. Like all toilets, Eljer tanks have a 1.8 gallon water capacity, so adjusting the flow will be the most efficient way of creating more or less flushing power.
Remove you Eljer tank's lid.
Tighten or loosed the screw on the very top of your flush valve, holding the float in place. The flush valve will be the plastic piece to the left of your toilet tank. Tighten the screw to raise the toilet tank's water level or loosen it to decrease the tank's water level.
Place the lid back on the tank and flush the toilet, checking to see if you have the water flow you want.