what's the most likely component that would make a Z run really rich?

carborated or fuel injection

To: Justin, the 280Z under discustion is fuel injected

is there anymore input on this problem? (the rich running injected 77 280 is there anymore input on this problem? (the rich running injected 280Z)

It would almost have to be a fuel injector. But, I have heard of some behicles not having enough spark and when the fuel enters the cylinders there is not enough spark to ignite all the fuel. Another thing to check is compression. If its burning oil or losing coolant you may have some serious issues and its better to double check than grenade a motor. let us know what happens. Another note, fuel pressure regulators, I doubt the car has any kind of evap system but look at to if it does. Im not particualrly familiar with that old of a Datsun. But all the stuff I mentioned is pretty much universal. Also, a product engineer from snap on tools told me one good piece of advice. Just google it, Ive had better answers than AllData

Thanks for responding Chris; the first thing I checked was the spark strength. It is fine. I'm about to go look at other components including the fuel injectors. I'll post the results. Thanks again-- deadmanwalking

Chris: fuel pressure was right on; the injectors checked out. The problem was unusual; the flap valve in the mass air sensor was stuck un the full open position. Removing,cleaning, lubricating and exercising the valve got it operating as it should. The rich running condition then vanished. deadmanwalking

yup, mass air sensor...water temp sensor can also cause that.