The title covers most of it, but the long version is as follows: My car is a 1990 bonneville LE. It has been running well for the year I've owned it with the exception of a replaced CPS and waterpump a year ago and 6 months ago respectively. It has progressively started to run worse recently, stumbling when going up hill with the cruise control on and accelerating in a stuttering fashion. At first it was only when cold, but after driving about 200miles and parking it for the weekend, it began acting badly all the time. Yesterday I drove to my brothers house. When I was leaving, the car started and ran for about 20 seconds as I adjusted the ventilation system to defrost and changed the radio station. It died abruptly and refuses to try to start. Checking the codes jsut gives me the ubiquitous "12". What now guys?

Start with checking fuel pressure. Then spark. Without those two you are not going to start.

Is it cranking over at all?? or is it completely dead?

did you check the wiring to the crank sensor? perhaps it wiggled loose or got caught in the drivebelt.

Indeed, or it could just be worn down and rotted away thanks to many years. Happened here suddenly too. Crank, no start. No codes. Wouldn't hurt to check this one out, if it'* it, the fix may be free.

If you have a tach, does it jump around when cranking?

It cranks over but doesn't make any effort at starting. The tach doesn't jump around, it just revs up to about 500, from the starter turning the motor I assume. I replaced the crank position sensor about a year ago, and had a **** ton of fun adjusting it with a feeler gauge, so I'm gonna be a litle pissed if it'* rotted out, but I'll check the wiring. How would I go about checking the fuel pressure? I can hear the pump running for a few seconds if I turn the key to "on" for a minute then start, but I don't know if thats new or not as I usually don't linger in the on position without starting.

Fuel pressure would be checked with a pressure gauge ($30 at parts place)

Although if you aren't starting that would be 0 pressure. On the fuel rail is a black cap. Looks like a valve stem cap on a tire. Take that off and being careful as it'* under pressure push the center to see if fuel squirts out. You should have fuel and it should be under pressure.

I have an Actron fuel pressure guage, $40 from Sears, better on sale. Must have at least 20 psi to start.

First thing I do in a case like this is to pour about 1/2 oz of gasoline into the vacuum connection on top of the manifold and crank.

If it tries or runs briefly then you have a fuel problem. If nothing, is spark. Can go from there.

Might want to download http://6007.us/cbdnr.pdf for the official way.

Since the tach jumps around, that means your crank sensor, cam sensor, and ICM are all fuctioning [however that doesn't mean for usre you have spark, it'* just a good likelihood you do]. Fuel pressure is the next step... autozone'* loaner program has one... i think. You pay a deposit, and take the tool and when you return it you get your money back in full.