Well, you could check a few things...check the fuel lines for cracks and such. Just take them off, plug one end and blow into the other and listen for leaks. Or you could put the fuel line into a cup of water, with the open end and the plugged end sticking out and blow...if there is a leak, then you should see air bubbles. If this is the case, go to your local hobby shop and buy more fuel tubing.
You should also check your glow plug. If you have had the t-maxx for a while and it is the same plug that came with the truck...change it. It is suggested that you should change the plug after breaking in the engine.
If the plug looks discolored, if the filiment looks burnt or broke, etc..change it. If it looks fine and you have a glow plug ignighter, put the plug into the glow plug ignighter and see if it "lights" up. If it doesn't, or looks weak and/or dim, replace it.
If that doesn't work, try fresh fuel. Nitro fuel should last quite a while if stored properly...ie in a closet away from moisture and changing tempratures.
And if after all that, you still have the same problem...check out
www.rccaraction.com and look on their forums for an answer. If you can't find one there...ask at your local hobby shop, they should more than willing to help you out.
