Still overheating

[78 280zcar]

Well I went and got a new fan clutch and It runs good, no overheating while sitting at a stop light but after I shut it off and let it sit for about five minutes and try to start it it starts but sounds like it just wants to die and it kinda sputters and idles really low does anybody know what this could be. Thanks

[2ManyZs]

If it's acting like it's trying to vapor lock, I would first check the water temp sensor and the air temp sensor... it may be trying to enrichen it like it would on cold start when it doesn't need too...

[mwz]

Does it snap out of that pretty quickly...i.e, how long does it sputter? Is it ingesting coolant? Sorry if I missed the history on this.

EDIT Keith's quicker than I am at this hour!

[78 280zcar]

It does it for a little while about a minute to be exact and then it idles fine. 2manyzs, is there anyway to test those two things the water temp. sensor and the air temp. sensor without having to just replace them and where is the air temp. sensor located at. Thanks

[2ManyZs]

Yeah, there's a couple way to test them, not only at the sensor itself, but also at the ECU, but, without a Factory Service Manual handy, I can't tell you the resistance values.....

If you don't have a FSM, you are kinda in the dark as far as testing values of the sensors, if you don't have one, I suggest you get one as it will be ten times better than any other manual like a Chiltons....I don't remember if the air temp sensor is in the same location on the 78's as it was on my 75, so I'll let someone else answer that one.

If you don't have one already, I know where you can purchase a new one for a resonable price... I can Private Message his contact info if you need it.

[78 280zcar]

I have a haynes automotive repair manual! In my manuel it says water temperature thermal transmitter, would that be the same thing as a water temperature sensor. Well if it is it says to disconnect the lead from it and ground it to a good earth, switch on the ignition and observe the needle, if it goes to hot then it is faulty. I found out that the air temperature sensor is on the map sensor or air flow sensor.

[78 280zcar]

well I did the test on the water temp. sensor and according to the book it is faulty. If that sensor is out would that be whats causing my car to idle like that. Any help, thanks

[mwz]

Like Keith said, I would really recommend a factory service manual dedicated your your 1978. The Haynes manual isn't the best reference.

The test you describe is for the temp gauge sending unit ('thermal transmitter'). The test verifies that the temp gauge works...it doesn't tell you much more than that.

The sensor that Keith was referring to is located right next to the temp sending unit if I remember correctly. It tells the ECU how warm or cool the engine is to change the fuel mixture appropriately. If it's giving the ECU a "cold" value on a hot restart, then the mixture will be too rich and cause trouble.

You mentioned that it is 'still overheating'...can you elaborate on that?

[78 280zcar]

Its not overheating I just thought it was because of how it was starting. Ok, there is two sensors right next to the sending unit, one is a thermotime sensor and the other is the water temp. sensor, would you happen to know which is which. Thanks

[mwz]

From memory, I believe one of them is smaller than the other...that should be the water temp sensor. The larger one that looks similar is the thermotime switch.

This 280Z fuel injection manual should help, too:

http://www.72hours.net/~zcar/280zfuelinjectionbook.pdf

[2ManyZs]

Sorry for the confusion, I should have proof read my earlier post and changed my description a bit...that's what I get for being up late....

The "Thermotime" switch is the one that controls the cold start valve, and the water temp sensor is for the temp gauge....

If I remember corectly, the water temp sensor has a red wire and a ground, so the thermotime switch should the one that has no red wire... whether it's the one on the left or right, I can't remember....

If I remember right, there are 3 sensors in the water neck for the thermostat, two in the front and one on the side towards the distributor... not really sure what the one on the side is for....:stupid:

[78 280zcar]

I think I'm going to change the water temp. sensor and see what happens, I found one for 20.00 at autozone. Thanks for the help guys. I'll post again to let you guys know whats going on and Merry Christmas.