Well it could be many problems.
Does the engine crank, but not turn over?
If the engine does not crank at all, or cranks slowly, it could be a problem with your battery. Check the battery terminals and wires.
If it does not crank, and you believe your battery is ok, check your fuses.
If the engine cranks, but won't turn over, it could possibly be your spark plugs, spark plug wires, distributor or fuel pump. The best thing to do is to get someone with moderate vehicle knowledge to do some basic diagnostics.
Just one.
I have a 1999 Sunfire and I have problems with the theft system too. Sometimes, I am able to pull the fuses and put them back and it'll start. Other times, I have to just sit and wait (for about 8 minutes) and then it'll start.
I have a 1996 Sunfire 2 door hard top that just cost me $160.21 total for the mobile team to come to my residence to replace the windshield. I was quoted as high as $270 so it does pay to call around for estimates.
just taking a shot in the dark but is that supposed to read where is the heater core really located on the 1996 Pontiac sunfire??if so its located under the dash of the car,towards the floor board behind the heat exchanger box..if you are asking where the heater core relay is ,,well there is no such thing so need to ask where this is.
I have the same problem with my 2004 Sunfire. Leave the ignition on for 10 minutes. Just let it sit for 10 minutes. No shorter than that time. And Should start.
Check for fuel Check for spark
It should be perfectly happy with 10W30. Many oil change places are now using 5W30 as their default. My '96 ran just fine with that too.
It could be a clogged fuel filter. It is located in the rear just in front of the gas tank.
I would start by checking the battery and fuses.
Well, that's just when they wanted to start it. :)
I recenlty got a recall on my ignition switch in my 2000 sunfire and I just took it to the dealer and they did it for free.
On my '96, they're right across the front of the engine, 4 in a row. They might be a little hard to see, so just look for the plug wires and follow them to the plugs. FriPilot