My Weller pyropen does not ignite all of the time despite it having gas and a really good spark from the igniter. Is this a common problem and if so how do i resolve it It will also turn itself off if you turn it side on.

Try cleaning the air gas mixer.

what do you want , look at the size of the tank and know it will not last for months on end

If it won't start, it is very likely either fuel or spark is lost at the engine. Is the engine getting gas to it from the gas tank? Do you hear the fuel pump turn on for 2 seconds with the key in on, not start? This 2 second period is to put pressure in the line and to the fuel injectors.

If gas is getting up to the engine, next check for spark. Buy a cheap spark tester, hook it to a spark plug wire and crank the engine over. If ignition system is good, you will see a blue, snapping spark on all of the spark plug wires. If you have spark, next check the fuel injector circuit. Post back if you need help with that.

If you have no spark, aha! your ignition system has failed. Now you really do need to check all your fuses before proceeding. Most common failure with no spark is an ignition coil, a bad ignition control module, or a bad crank position sensor. Many other possibilities, but those are the most common.

Gas (condensation really) may be freezing and constricting flow. Try warming the tip a bit with a hair dryer see if it goes longer.

Any butane will work, but the big name-brands are usually filtered better and less likely to cause problems. The biggest issue is the nozzle -- there are a lot of different sizes. Any Weller butane can will fit perfectly (usually cheapest at the local Sears store), but any can with multiple adapters will also work.

If you have an old can that fits, save the nozzle when it's empty. It should fit a different can if you can't find a can that fits the tool.

Not enough information. That's an extremely vague description of the problem. There's no way to suggest a fix without knowing more about it.

Does it spark?
Does butane come out of it?
Is the cylinder full?
Do the switches move properly?
How old is it? How much use has it seen?
Is it an intermittent problem, or constant?

A soldering iron is composed of a heated metal tip and an insulated handle. Heating is often achieved electrically, by passing an electric current (supplied through an electrical cord or battery cables) through the resistive material of a heating element. Another heating method includes combustion of a suitable gas, which can either be delivered through a tank mounted on the iron (flameless), or through an external flame.

I have the same soldering iron and have found for this problem, the replaceable tip has worn out.
All you need to do is buy a replaceable tip of your choice. The tips are a consumable part that wears out.

http://www.mcmelectronics.com/

Does it spark?
Does the butane come out?
How old is it, and how much has it been used?
Did you put cheap butane in it at some point?