Crank but no start

[tiegsd]

Hello all,

Having a bit of a problem with the Z, she will crank all day, but won't kick over and run. Replaced the fuel pumps, have 51 psi on the fuel rail when pumps running. No codes, only code 12 when I jumper the ALDL pins.

I'm decent with electronics, but never been much of a car mechanic. Intend to just go through the FSM troubleshooting steps for the condition I have.

Background is that last year I was able to start and drive the car, but upon start it would run and the rpms would slowly drop and the engine would start to stumble and run rough after a few minutes. SES light would then come on, rpms would bump up for a second, then car would run smooth for a couple minutes. Then SES lig ht out, engine slowly drop, stumble and rough running until SES light on again, repeat process. Car did this even when warm and I was driving it.

Early this year, car wouldn't start anymore, but would crank. Thought maybe failing primary fuel pump, so pulled the assembly, checked winding resistances, primary pump was 115 ohms, secondary pump 5 ohms, so looked like failed primary pump, hence pumps replaced.

Additionally, battery would be flat after sitting for 2 weeks or so, ended up replacing battery, but still have crank but no start.

Wanted to see if anyone had seen these symptoms, or has a hunch on which way to go with troubleshooting?

Car is 1990, no mods other than Haibeck chip, VATS bypass.

Thanks in advance!

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