Foodsaver v3400 series won't vacuum/seal. When I turn on the machine it makes the vacuuming sound with no bag present.

It sounds like you are having some issues with your FoodSaver vacuum sealer. Here are a few things you can try to troubleshoot the problem:

1. Make sure that the FoodSaver is plugged in and turned on.
2. Check the sealing strip on the vacuum sealer to make sure it is clean and free of debris. A dirty or damaged sealing strip can prevent the vacuum sealer from working properly.
3. Check the vacuum bag to make sure it is properly positioned in the vacuum sealer. The bag should be inserted with the open end facing the sealing strip.
4. Make sure that the bag is not too full. Overfilling the bag can prevent the vacuum sealer from working properly.
5. If the problem persists, you may need to take the FoodSaver to a repair center for further diagnosis and repair.

Perhaps the bags you are using are not suitable. If they are too thin it will not vacuum air out.

Does it try to vacuum but never flattens the bag? Make sure the bag you are using is completely sealed on the opposite end. Otherwise, the seal on the sealer is probably allowing air to leak into the sealer. If it has a foam sealer, I've found it sometimes helps to run the foam sealer under water, squeeze out the excess water, reinsert the foam sealer (make sure it is seated all the way) and then try again to seal the bag.

wow when I ran my food business I seemed the only one that could get this thing to seal right every night , Im gonna say it was because I wasn't in a big hurry , these machines work great but there not fast it takes sometimes 5/10 minutes to get a good seal on them , and you cant overload them either , when it comes to these less is more , makes for a easier time using them

allow the food to stop about two inches from top edge of bag , and wipe any loose food from the sealing surface (inside) as this will affect the seal as well

press release on top cover , I had someone use mine 1ce and they pressed "seal" with no bag in machine it did exactly that it stuck closed, tight too !! one touch of release button on top cover and it popped open

you are not using a "good" bag. Make sure there are no holes and that the bottom and sides of the bag are properly sealed. It will run all day and not pull the air out if the seal is broken anywhere.

Have you checked to see if the element is intact?

if not, http://www.elementsandmore.com/

Sounds like the foam seals are leaking. Go to their website to get replacement parts.

http://www.instructables.com/answers/How-to-fix-Food-Saver-Vacuum-Sealer/

The tape trick didn't work for me. Had to cut the wires. Works for now.
.