300zx won't start

[913ZXTT]

i have a 91 300zx TT and sometimes it won't start..in the morning it'll crank right up but after driving it for a while then shutting it off. if i try and crank it it'll either start right up then the rpms will drop and almost die or not start at all..I am getting fuel as i can see smell it. what would cause this..

[evildky]

PTU? if you problem is intermitant spark it is likely the PTU, located on the front of the passanger side timing belt cover, be sure to check your injector and coil pack connectors as well as the mas connector, they have been known to deteriorate and cause these kinds of problems

[Milo (San Antonio)]

Agree. It's most likely the PTU. Start by cleaning the connectors and using dialectic grease on them. But note, a lot of times it's not the PTU itself but the harness connections to said PTU. The PTU harness is actually located in a very hot place and after time the wires oxidize and also become brittle. This is unfortunately is a common problem with the Z32, which requires hardwiring of the subharness to eliminate this (if a 90-93) 300zx, if later year, consider replacement of harness. Another helpful tip is to relocate the PTU, one location I prefer is the next to the air intake as it is a cooler location.