2005 grand prix somtimes will start but sometimes needs jump to start but seems like all power is good lights and everything works could it be soilnoid????

You have a bad cpu likely. You will need to bring it to a dealership so they can run diagnostics

Better check with a test light for power to the small wire that goes to the starter from the key switch. If no power need to check for a neutral safety switch or fuse. Or the starter you got is bad. Alternator will not cause not to crank over

It could be the key switch, or the neutral safety switch.
You would need to know if you have power on the small wire on the solenoid that comes from the key switch when the switch is in the start position. The neutral safety switch is in the circuit between the key and the starter.

Used parts such as starters and altinators don't last. It might **** but it sounds like you need to buy a new starter,altinator, and battery. Or just start with buying one at a time.

REMOVE THE DIC CENTER SEE IF IT IS GETTING POWER.SHAKE WIRES SEE IF DIC CONTROL WILL LIGHT UP WITH IGNITION ON ENGINE OFF.IF POWER GOING TO DIC CENTER AND SHAKE WIRES YOU STILL DONT SEE THE OIL DISPLAY LIGHT UP.DIC CONTROL COULD BE FAULTY.

Try resetting the alternator, if that doesn't work try changing the battery

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Could just need a tuneup, new spark plugs and wires, fuel filter etc. Is the check engine light on at any time?

replace blower motor...but first check wires on blower motor see if u have power if you do then blower motor is out

If you deffinitely have fuel and spark then it must be a timing issue.

It's ok have fuel & spark but if in the wrong place at the wrong time it won't start. Check that the timing marks to and bottom are correct, the belt could have jumped.

Is it back firing into the inlet when trying to crank? Like a loudish popping noise.

fuel pump , not enough pressure. check the pressure.