i recenly got the problem of if i let my truck sit over night or at work for awhile it wont start i replaced the battery and alt. when i turn the key over my volts are real low and it will just sit there and crank. ill do it like 10 times and it will eventually start put the volts will be low untill i hit the gas please help

 

Let me see if I have this straight. You let your truck set over night or for awhile and then it will not start? Do I have this right so far? Then the volts will drop while cranking it? It starts when you press the gas?

If it starts when you press the gas you have a bad fuel pump in the tank you are using.

Volts will drop if you have to crank it for a long time to start it. Yes they will go up when you press the gas and cause the alternator to pump more juice.

 

Sounds like there may be a short that is using power. I'll be honest i don't fully understand your problem.
The volts will dip if the engine is not running and turning the alternator to generate power.
It cranks but it wont start? Sounds like a fuel issue, which Mr. Zero already mentioned.