EZee

I just finished up a timing belt change on my '86 NA, including a new water pump, CHTS, belts, hoses, etc... The car is running great. Oddly, the injector cooling fan is now working. It never worked before, and frankly, I didn't even realize that the car had one until I heard it run after I shut the car off. I'm guessing that the CHTS controls the fan and that changing it "fixed it". Is that true, or is there something else going on?

NismoPick

Did the coolant temp ever go above the middle of the gauge?

I imagine the Z31 cooling fan is setup the same as the 280zx... if the coolant ever got above ~220*F, when the engine is shut off, the cooling fan will come on for 17min. It is activated by it's own sensor in the thermostat housing.

There should be a section on it in the FSM: XenonZ31 FSM Download and Haynes manual.

EZee

The coolant temp needle was pretty close to the center, maybe slightly past. The Haynes manual really only talks about R&R of the fan (no system operation), and the only thing I found in the FSM was in the wiring schematic. I'm sure there's more, I just couldn't find it. The system coming "back to life" could be coincidence or maybe disconnecting and reconnecting some of the plugs re-energized it.

PredatorZ

The swiping action of plugging and unplugging connectors can break a buildup of corrosion and re-establish a connection, most of the connectors on s30 thru z31 are not water tight, so moisture and time will leave corrosion and mineral deposits behind. Most likely that's what happened, at least that's what I'm guessing. I just ordered a kit for my 280zx from Fricfrac to replace a lot of the connectors with nice water tight one's, they have a seal around the wire end and the mating ends, so everything stays nice and dry and clean for a long time, hopefully !