I have an L225 that starts somewhat hard. I glow plug it for about 40 seconds when its 40-50 degrees out and it will start for a second or so then die. I have to do this 4-5 times before it takes off. The battery is new, glow plugs new, filters have been changed, new fuel etc. Any thoughts? Also, is there a faster heating glow plug available for these? Could this be air in the fuel line?