Well, lets see where to begin. I own a 2000 Civic Sedan LX that will turn over and over all day long but will not catch and start. I have done practically everything to this car and just now recently had it taken into a shop... thinking it must be the timing belt. Nope. It's not.. and now the Mechanics are confused also and don't know why It won't start. So to back up a bit. I Have Spark, I have fuel, and I have air.. It seems like there is no compression though at all. Figured Timing belt could fix that... timing belt is fine. Checked for bad fuel pump.. water pump.. main relay.. plugs and wires.. everything seems to be OK. I just cannot get any compression in the cylinders. The last thing I remember when driving the car before I parked it in my garage was that it sounded like it was hissing almost whistling... does this maybe mean there is a broken seal somewhere? That's the last thing I can think of... all in all I need some help, and so do the mechanics apparently looking at my car lol. Any suggestions? Maybe the pistons are causing a no start?? I'm so stumped. By the way if anyone does know what the problem may be.. what do you think the estimated cost would be to fix this? :(

Check each cylinder's compression. How the pressure builds will tell you if it's the valves or rings. You may have a blown head gasket. Has your Civic ever overheated?