1991 Buick Century engine dies after warm up

Are there any codes? When it refuses to start, have somebody crank it, while you check for spark and injector pulse, that should tell you if there is an rpm signal.

When it dies, can you tell if the fuel system was too rich or lean.

26 is a quad driver fault and 42 is est circuit problem.

I'd still check the crank sensor circuits, first. I'm not saying replace the sensor, I'd have to make sure there is an rpm signal.

If you have a scanner or can borrow one, with the engine cranking, it should show if there is an rpm signal.

You said you didn't have spark, after it dies, if there is an injector pulse with the engine cranking, then there should be an rpm signal.

The purple/white wire and white wire at the ignition module, should have a pulse on them, with the engine cranking. If you have a digital multimeter with a tach--dwell-- duty cycle setting, any of these settings should react to a pulse. I believe radioshack has a digital logic probe that will react to a pulse.

You might be able to check for voltage on the coil side of the fuel pump relay, with engine cranking. I don't believe there would be voltage on the coil side without an rpm signal.