Why is my truck doing this

If the clicking is rapid, it's likely a bad starter or solenoid. If a single click, the battery is probably low, which could be a bad battery or alternator..... If gasoline is coming out the air intake, it might be a sticking PCV valve, but it's more likely that the fuel pressure regulator is leaking and may have even filled the engine oil with gasoline. You should have the fuel pressure regulator replaced and the oil and filter replaced. And if this is the case, that clicking might be caused by the starter unable to move the engine because the cylinders are filled with fuel. You may have to have the spark plugs removed to get the fuel out of the cylinders.