D51256 when trigger is pulled air escapes and nailer will not fire

SOURCE: I only shoot one nail and the rest is air

It sounds to me like the spring within the magazine is not functioning properly. WIth brad nailers, it is that tension that places the nail into the proper position for firing. This may be as simple as cleaning the loading area and slightly lubricating it. WIthout seeing the actual gun, I cannot tell you for sure. If you are not sure of this, look for a professional tool repair shop in your area. They will be listed under industrial tool repair.

Dan

SOURCE: My D51257 nailer will not

If air escapes from the trigger as soon as you connect air, most likely bad trigger valve or needs orings in valve. If air leaks from the trigger when you attempt to fire the gun, then internal orings are at fault. If leaks when attempting to fire, remove head and lube all the orings with silicone paste lube (sold at Lowes or swimming pool supply) and retest. If gun fires after lube, order oring kit or keep using till trouble. If you need to replace the trigger valve, remove nails for safety and the trigger to expose the valve. Remove the rollpins holding the valve into body. Apply air to gun and catch the valve as it pops out with a gloved hand (use caution because the valve could come out with force).