'92 Skylark Quad 4 intermittent crank, no start, no codes

This car has 99,000 mi on it, engine was replaced at around 50,000 mi, but not by me. Anyways, every now and then it will just crank and crank and never even try to fire. We leave it alone for 6+ hours and usually it will start right up. :confused: No codes stored in memory (used Snap-On red brick) but the data it gives me as it is running says this: QDM-B Fault - Yes. I have no idea what this means. I'm suspecting a crank sensor issue, but I have no idea where they put it on these damn things. :banghead: I can tell you its not near the crank pulley, though. Also while using the red brick, I got a flash code of 12. Is this GM's pass code? I'm so much more used to Ford electronics. Any help would be great considering my girlfriend really needs her car back as soon as I can get it.

Thanks in advance,

Mark

Ok, round 2. I finally found the crank sensor and replaced it based on what the car was doing and what was cheapest and most logical. By the way, the crank sensor is under the intake in front of the starter. It ran fine for about 2 weeks. I just had a feeling that it wasn't the problem and sure enough, the stupid car died on her while driving this time. I just happened to be right behind her, so I pulled over and pushed her into a parking lot. I'm going crazy because this damn car won't act up if I have any diagnostic tools with me. It will only die with her. Anyways, this is the first time it died while driving. Her parents are considering selling it and I'm wondering the same. Does anyone have any ideas at all??? I removed the coil pack and didn't notice any carbon tracking or anything like that. I'd like to fix it because there's no way she can afford a car right now.

When it won't start, does it have spark? Does it have fuel at the proper pressure? Are the injectors firing? My guess would be fuel related, possibly a pump going bad?