... And now the car own't start.
 

I have a 2.0 liter automatic transmission 2002 Mazda Protege LX.

The accessory belts have been squealing on this car for a while and I noticed there is a fair amount of oil leaking on the left side of the engine. I have been unable to pin-point exactly where the oil is coming from- It's covered everything. I changed the crank shaft seal and while doing so, replaced the harmonic balancer, timing belt, and battery as well. I double and triple checked the timing and I'm convinced it's absolutely perfect. I've re-connected and checked every wire to ensure I didn't miss a ground or anything.

Now when I attempt to start the car it turns over with no problem, and once every 4-5 turns it will act as if it's about to start with a slight "sputter" if you can even call it that. However the car never actually starts. I pulled the spark plugs and they are covered in gas (makes sense seeing I'm not getting a successful ignition) but also seem to be covered in oil as well. I shined a flash light down to peek at the cylinders and it looks as if there may dark pools of oil sitting in with each piston (all 4 of them). Or, the pistons may be dark and I may be seeing un-burned gas.

So my questions:
- What might be causing the car to no longer start as it did previously?
- Why is there a pool of dark liquid in the cylinders? Is this normal? Is this a valve seal or head gasket issue?

Thanks much!

All of what you said sounds like incorrect valve timing. Sorry. One easy way to check is put the vehicle at TDC compression no1 cyl. Put compressed air into the cylinder and it should not "leak out". In other words the valves will be closed. weld a tube to an old spark plug end , screw it into the cylinder and then connect a compressor airline to it.If air just streams in and into the exhaust or inlet you have got a bent valve or incorrect valve timing

After giving up for a little while, I FINALLY fixed the problem the other day.

The newly purchased harmonic balancer is about 1/2-3/4mm thicker on the back side than the original one. This was causing the teeth to slightly mis-align with the sensor. Did some finagling, and bam! Started up without a hickup. Ridiculous.