The engine starts and idles fine, but if I turn it off and try to start it again, it runs rich with fuel and will not start. I have to leave it for about a hour before I try starting it again. I've replaced the fuel regulator and still have the same problem. I cant seem to find the source to this problem, any suggestions?

 

Welcome to ZDriver!

Make sure you've downloaded your factory service manual just to get yourself more info on your 280. It's a freebie at XenonS130 - S130 Reference along with other cool docs. Your FSM is loaded with inspection and troubleshooting pages that are pretty easy to follow, so check those out and see how many of them might deal with your issues at this point.

Let us know what you've tried after that and let the 280 guys give you their input. You can post some pics here too and maybe a bit more of the history of that Z.

Thanks and welcome again!

 

You sure it's running rich and not lean / no fuel? Have you pulled the spark plugs to verify?

The CHTS and AFM are the two main sensors controlling fuel delivery. Check their outputs (per FSM) and connections for corrosion.