02 e250 wont crank

[bugg-z]

my uncles e250 has been sitting in my backyard for nine months now. when i try turning the key i dont hear the clicking as if it were the battery that was dead. it had alot of corrosion on the connectors but i cleaned it and sprayed it with corrosion cleaner but still wouldn't crank also i can jump start it but even when i do it lags when cranking. it sounds to me like the battery is dead but something else is wrong besides it cans omeone help me out.

[maudeb]

chk the volts on battery with meter try cranking if bat volts is not 12plus volts before trying and falls real low when trying to start then charge battery