Help! 97 won't start, pulling out hair

[ta2tony]

This is my first post, I have searched but not seen a problem like mine. My girlfriend drove her 1997 c1500 5.7l vortec 5 speed 2WD (200k miles) and parked it. In the morning it would not start. It turns over but will not fire. Furthermore, when turning it over, the motor seemed to 'tighten' up as though it didn't even want to turn. There is no 'security' light and the diagnostic showed no error codes when hooked up the the OBD-II.

Here's the stats: Pressure gage on fuel line reads 66 pounds when cranking. Got spark at the plugs. Turned the engine till #1 compressed, mark on the balancer matched the TDC mark on the timing chain cover and the distributor rotor was pointed at the #1 location, so it appears the timing is OK.

We replaced the fuel pressure regulator, fuel filter, and spark plugs. The distributor cap and rotor are fairly new. We also dropped the exhaust prior to the catalytic converters in case they are clogged. The motor turns more freely now but still won't start. Aside from throwing a timing light on it, I don't know where to go from here.

You all seem to know your Chevy's, any ideas would be greatly appreciated.

[horse482]

Could be a crank position sensor.

[Blue Bowtie]

Or cam position sensor phasing.

[texandrvr]

Take the cap off the distributor and try to twist rotor. If it has freepaly, then take the distributor out,mark it of course. Give it a close inspection, look for the gears to be worn or gouged. This wear causes the rotor to bounce, will still show spark but the computer cant get it in time because it moves all over. It will line up right but when you start it thats when the timing goes off, not when its sitting there. Worth a try, you dont have to buy anything for this test. Good luck

[chuck16]

Check for wires that have been munched through by lovely little rodents. I had a sensor near the Air Intake on my 4.3 L that had been munched by rodents and it stopped my vehicle from starting. I know it's odd to the think that mice can do that to an engine and I never thought of it before; that was until i experienced it. Check all your wires and Vacuum hoses under the hood.