Tornado grenade problem.
 

I've replaced the fill valve on my impact tornado grenade so it holds gas fine. The only problem is when I pull the pin on the grenade it explodes as soon as I pull the pin. I've followed all the instructions and maintenance steps in the manual exactly yet it still does this. Any idea as to why that would be? I emailed customer service four days ago but they have yet to reply back.

WHich type of nade?

The only reason why your impact would detonate as soon as you pull the pin is one of two reasons...

1. You're missing some of your tumbler pieces. You should have two long cylinder type pieces, one small washer, and one half moon piece. If you're missing any of these parts, the tumbler assembly might counter balance as soon as the pin is pulled and detonate.

2. You're not putting enough gas in your grenade. The tumbler system relies on the pressure of the gas to sit the assembly together so when you pull the pin out, there's no pressure to hold the assembly together.

No pressure could also mean that you are leaking your gas somewhere too...

Did a water submersion test earlier when it was leaking and replaced the fill valve. I have all 4 pieces for the assembly grouping as well. It is an impact tornado.

Do another submersion to ensure there is no more leaks... the only thing it can be is that your grenade doesn't have enough pressure to support the tumbler column and when you pull the pin, there's nothing there to support it so it counter-balances and detonates...

When you fill, listen to the tank as you do and when it doesn't make any more noise, your ‘nade is filled to full pressure. Dunk it in water for a couple minutes in a clear vessel and watch for bubbles, if there are no bubbles, try pulling the pin. If there are bubbles note where they are coming from. Also, leave the bottom "priming / safety" cap off, this way you can see where the bubbles are coming from, from the chamber or from the valve itself.... I'm just rambling now, so I'll leave it at that...

you are filling it like a mag yes? upside down?

it can't go if the stack is in place.. the only way it can detonate is if the trigger stack is deflected

so you have either

1. not enough gas in the grenade to lock up the stack
2. a defective trigger stack that does not hold when the pin is pulled