Truck wont crank

Well ofcourse I was heading to work and got in my truck and turned the key and didnt even turn over, well it kind did but extremely slow wuoldnt even consider it a turn over, so called my friend over to come jump me, he drives a chevy s10 and hooked up cables and nothing not even a turn over, next day i went outside to to try again and it kinda turned over.. well better than it did yesterday so I checked my signal wire going to the starter and hit the sillinoid thinking mayb it was on a dead spot, my bud came over to jump it and just like yesterday the volts on my volts gauage went up to around 9 which is were its always at when i start my truck and nothing not even a turn over... so later on i turned my lights on to see if they would stay on and they drained the battery volts on the guage extremely low and only took 10 seconds, i cant get a voltmeter from my grandpa till monday so just looking for ideas of what it might be, im thinking starter or battery cause it obviously isnt the alternator...If it was running and voltage dropped id understand but never did that so house to be starter or batter right?

See if you can hook up another battery temporary and see if it starts.

Battery probably has a bad cell in it causing it not to jump start or hold a charge. Same thing happened to my truck and i had to drive it home 5 miles with a jump pack hooked up to the battery. Id say replace the battery and go from there

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You can try a new battery. Are you getting short clicks then nothing? If so that could be your starter.

Also get under there and beat the starter a little bit. You'd be surprised how well it works haha.

I did hit the sillanoid to get it off the dead spot but you dont wanna hit newer starters cause of the permant magnet and Im doing a load test on the battery tomorrow