I've got an 87 NA with a hot start problem and I'm starting off by replacing the coolant temp sensor which looks to be under the alternator. Anything special I need to know? I'm assuming I'll need to bleed the system when done, do I need to reset the ecu when finished?

 

If you remove the alternator you can easily access it.
It is not necessary but it does make life a lot easier.
NOW..undo the sensor from the connector..Carefully.. you can use a dental pick or small screwdriver to get the wire retainer moved on the clip so that it will allow you to take it off the Sensor.
Loosen the sensor until it is just about out..Have the other one in hand.
QUICKLY take out and put other sensor IN.
It will only lose about an ounce or so..You will not have to bleed anything.

..and you can't "reset" the ECU..it doesn't even notice.

 

Thanks. It looks pretty straightforward and I figured removing the alternator would be the best course of action, as it's a pretty tight fit otherwise. I wasn't sure how much coolant i'd lose, and honestly couldn't find mention of anyone doing this actual procedure. Hoping that this is the only problem and the hot start issue goes away. The car has been dead reliable up until now, and it looks so good, it's embarrassing when it doesn't start.

 

Hot start could also be related to the fuel pressure regulator control valve. W/respect to the water thermosensor it can be checked at the ECU (pin 2I Green/White wire) as it should read 2-3 volts w/key to on and engine cold and as the engine fully heats up the voltage drops to .5 volts.

 

If the FPR control valve is bad or suspect, are there any other conditions, i.e. rough idle, etc. that would show up? Car has been running flawlessly up until this point.

 

Post #7

https://www.rx7club.com/2nd-generati...roblem-227533/

Plus the vacuum hose should be free of fluid (gasoline).