Assistance help..4 hours of failure
I agree with Ken Towner that sometimes the impeller can seize, even if it is just caused by the beneficial bacterial cultures that perform the biological filtration growing on the magnetic impeller and in the impeller housing. If you are cleaning the filter and then trying to get it to prime, make sure you also clean the impeller and the impeller housing (the hole the magnet goes into), using a toothbrush is an effective method for cleaning.
Given that if you try to plug the unit in you will be able to hear if the impeller is spinning or not, I will presume you are able to determine if the filter is not priming because the impeller is not spinning. If it is not spinning, and you have cleaned it and inspected the surfaces for any rough spots or breaks that can stop it from spinning, then you may need to replace the impeller or the entire unit.
If the impeller is spinning, which I am thinking is most likely the case, and sometimes even if it isn't spinning at first, there are a few different ways to prime any canister filter. The problem is caused by air being trapped in the unit. The solution is to get the air out.
Fill the unit with water:
Lower the end of the water return hose coming from the filter. Put it in your water change bucket on the floor. Alternately, simply raise it above the water level in the aquarium. The pressure of the water from the aquarium can trap air in the filter, so if you raise it above the water you're making less work for the pump.
To fill the unit, attach your gravel siphon cylinder to the water intake hose, then lower the bottom of the cylinder into the tank water so that the gravel vacuum opening of the tube is pointed upwards. As you lower it into the water, the cylinder fills up. Once it is full, raise it so the water in the hose jumps over the tank top. The water in the cylinder will start to empty, so submerge it back into the water to keep the water flowing into the canister. The water should fill the canister and start to fill the output hose. You can try to plug the unit in as this is happening, or stop and secure the output hose back into the tank first. A small amount of air in the hose will not now affect the pump starting up. Then plug the unit in.
A much easier way of doing this is to have a decently powerful powerhead in the tank. Simply put the canister's intake tube in a position that causes the powerhead to fill the canister. You can make a temporary seal between the tube and the powerhead output by closing your index finger and thumb around them, directing the water into the hose. The powerhead should be able to get the siphon effect started, and it doesn't hurt to continue to hold this connection until the canister is filled, but it might not be strong enough to raise the water back up to the aquarium. That's fine, all you need is to fill the canister. Again, reattach the output, (or secure it in a bucket on the floor if you want to test the results first, and plug it in.
One last trick: I have had filters I've had to "jump start" by playing with the plug. Of course, be dry and not standing in water when you do this! Place the plug in the opening of the electrical outlet, and push it in far enough to make the connection. You'll be able to hear the impeller seize or start to spin. If it seizes, withdraw the plug and then move it forward again. You're not pushing the plug in and securing it into the outlet, but rather just touching it to the metal within to close the circuit and get the electricity flowing. You can easily disconnect and connect the plug - there should be no force involved for you to pull the plug back, or to push it in. Touch, touch, touch, ... and most water pumps will start up if they are in working order, once it catches and starts spinning, go ahead and push the plug into the outlet securely.
Advice: Spending $15 on a titanium aquarium grounding probe that plugs in to a grounded electrical outlet, preferably with a GFI (ground fault interrupter) is well worth the cost as compared to being electrocuted by reaching into your aquarium when unaware of a free electrical current flowing in the tank due to faulty heaters and water pumps, or lights falling into the tank. Do a google search for anything you're not familiar with here.
Always keep in mind where your biological filtration surface area is in your filters and in the entire system. Do not kill the beneficial bacterial cultures that perform your vital biological filtration by thinking you need to "clean" or replace your filter and aquarium. There is a huge difference between our definition of clean, and nature's definition of established. Google this if you don't know what biological filtration is. Without this your fish family can die.
Lastly, if your filter does not prime after these attempts, set it up on the floor with both hoses in a bucket of water (or raise the canister to the height of the water level in the aquarium and use that body of water for this). Securely attach a water pump to the input hose. Plug that in and let the water flow through the canister. As the pump is running, plug your canister in. If it does not continue to work after unplugging the pump, the unit is defective in some way. This method is more effort on your part, but it is better than holding the "motor" part of the canister lid upside down with the impeller in it and plugging it in to visually see if it is spinning. Running water pumps dry will damage the impeller and impeller housing, and you may have to replace the entire unit because of such damage.
I hope something here might help! Read More At : Filstar xP-XL extra large Canister Filter...