The back cover popped off my pulsar wrist watch and it seems to be too small to fit where it is supposed to. Was there some sort of a gasket that may have broken and can i buy a new one?

Many watches the back panel (that rest againt your wrist) pops off. Look for an indention, if you see one place a small screw driver in it and pop off the cover. Some also have nothes lining the diameter of the back plate, those are made to screw off, there are special tools to accomplish this task. You can use small tools to rotate and release the rear covers on this type of watch but you must be very caseful not to scratch or damage the watch surfaces. Most watch stores can replace the battery for you for free or really cheap.

Your watch is a solar powered watch and normally you don't need battery change .Nevertheless,if (as it is an old Casio model),you are convinced that battery is the cause of your problems,then replace.
1) You have to be absolutely sure that you are able to carry out the procedure.
2) IMPORTANT!! Pse note that the specific battery IS NOT an ordinary battery as it is rechargeable.DO NOT TRY TO REPLACE WITH AN ORDINARY ONE.RISK OF EXPLOSION on your wrist.+total damage of the watch.New battery has to be exactly the same with the old one (ID.code).Can be ordered on E-Bay,I suppose.
3)TOOLS:Watchmakers screw drivers + philips small size screw driver (for backcover screws) + watchmaker tweezers + 2 finger rubber gloves.
Turn the watch upside down and carefully remove the four screws (try not to loose them).Remove the strap if needed.Gently remove the back cover.Pay attention as there must be 1 or 2 tiny springs embeded on the mechanism.Keep them in place and try not to loose them.You have to remove the plastic cover (pay extreme caution to the spring/s) in order to have access to the battery.Unlatch and remove (if needed) the battery holder ( if can be removed-remember the position to put it back correctly).Take out the battery and check for possible leaks.Check the battery compartment cleaness.DO NOT TOUCH WITH BARE FINGERTIPS THE CONTACTS OF THE BATTERY COMPARTMENT.DO NOT TOUCH THE NEW BATTERY ON BOTH SIDES WITH BARE FINGERTIPS.Use the finger gloves.Put the new battery in place (do not force) and secure back the battery lamina holder.There is a AC(All clear-reset) contact on the mechanism.Using the tweezers touch one end on this contact and the other to the metallic body of the mechanism.Lift the watch very carefully(as it is,upside down-without disturbing spring/s) and check if display is activated.By paying much caution put back the plastic cover correctly in position PAYING CAUTION TO THE SPRING/S. Clean up the back cover,gasket,and gasket furrow from dirt as good as possible.Check the gasket condition.Replace if needed.Apply a little amount of special gasket silicon compound all around the gasket,both sides.Put the gasket in place.Put back gently the back cover and screws in position.MAKE SURE TO POSITION THE BACK COVER CORRECTLY(in place and not upside down).Press it gently when in correct position before you screw.CHECK ALL AROUND FOR CORRECT CONTACT. DO NOT SCREW TOO TIGHT,DO NOT FORCE.Screw with fingertips until you meet resistance.
I hope this will help.
BRegards

if it's automatic it means the movement of your wrist keeps it wound up ,but if it's not been worn for long time you can still wind it with the winder, if it still doesn't work it may need to go for a service at the jewelers.

when you look at the back are there three small rectangular indents evenly spaced on the edge on the back? If so you'll need a special tool for opening waterproof watches. the tool adjusts to fit the three indents then press down as you turn counterclockwise. you can find the tool on amazon.com or your local jewelry store. make sure the gasket is in place and not damaged before screwing the back on.

here is a link to the tool
http://www.amazon.com/Pavilion-Professional-Waterproof-Adjustments-Caseback/dp/B000K3SK0Y
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There is usually a way to remove the crown and stem together so that the movement can be removed from the casing.
Have a good look over the movement and see if there are any identifying marks and let me know what you find. Alternatively, post a photo of the movement.

mcdevito75 Here, Pulsar a quartz watch. If you lost the stem, the mechanism holding it into the watch maybe damaged, this mechanism also turns your Pulsar watch on / off. Best Bet, visit a small watch repair shop in your area, have them take a look at your Pulsar watch. You could replace the stem yourself but first you"d need the right size stem, (hard to get) then if the mechanism holding the stem in is damaged you"ve wasted your time. Your local small watch repair shop can let you know, and they usually don"t charge to have a look.

Follow this link and choose the way you wish to contact PULSAR: http://www.pulsarwatches.com/home2.asp#Contact_PULSAR Rate me, plz.

I suggest that you got to "www.breitling.com" and after getting past the pretty pictures you click on "maintenance centers" and find the one nearest you.

You can get into difficulty replacing batteries and it is not worth the risk for the small cost saving.

One fairly frequent cry for help is because the owner can't get the back on again. Also since watches frequently include gaskets to keep water out, difficulty can be experienced in fitting the back and maintaining the seal.

I believe a local watch repairer will replace the battery for around 5$ that should include the battery, depends on the person.

Generally the battery is replaced by opening the back cover of the watch, in some cases special tools might be required.

sorry to have bothered you, I broke the fixing whilst trying to get the battery out so will have to buy a new one! Why did I bother to try? the new battery has cost me about half the original price of the watch. What a terrible "throw away" society we live in. Thanks for your prompt response will keep you in mind for future problems.