[280z/300zx]

I've been haveing this problem lately with my 77 280z not wanting to start up after its sat for a little bit and its cold outside. For some reason when I go to start it up in the morning it will take about 5 tries to get her to stay started. Every time it will turn over, run rough at about 500rpm and then die. This will happen like I said about 5 times untill the running rough justs smooths out and runs fine. I went through the whole cold start system to find out that it is related to the thermotime switch. For some reason if you disconnect the thermotime switch the car will start perfectly when cold outside but will idle a little rough at about 800rpm untill it warms up. I know this is due to the cold start system being unplugged. However if I leave the thermotime switch plugged in so the cold start system does work the car doesn't want to start up good. So why do you think this is happening. I'm going to try to use a different thermotime switch to see what happens but this problem really confuses me. Any help would be great, Thanks

 

[Ian L FIC]

Sounds to me like you have a bad thermotime switch. It could be turning on the cold start valve when it really isn't needed, causing an over-rich condition. Is there excessive black smoke when the engine is started cold? If so, this is probably the case. Trying a different CSV will hopefully reveal the answer. Good luck!

Ian

 

[Ian L FIC]

I mean thermotime, not CSV...N/C

N/c

 

[shane280z]

Not Much Really.....

Yo 280z.
Its time to do a tune up and stop using 83 -85 octane gas. Adjust your valves. Change your oil and oil filter. Install new NGK spark plugs. Install a new fuel filter. Get a new distributor cap WITH matching rotor.....go to Nissan for the Factory ones and not AutoZone....Get a new air filter. Do these things now and you should not have your current problem. Also check your battery when starting your Z. If voltage drops signifiantly then your alternator is beginning to go or your fan belt is worn and needs replacement to tighter specs. So there really isn't much wrong with your Z. Just wants a bit of TLC from you. Have fun. shane-

 

[280z/300zx]

Re: Not Much Really.....

Actually it has new rebuilt motor with under 3000 miles on it along with all the stuff you mentioned to do, except the air filter is a k&n cone filter intake. I also change the oil every 3000 miles or 3 months with a new filter to make sure she runs nice and strong. As far as the battery goes I'll check that out, but it still doesn't explain why when I unplug the thermotime switch it starts up fine. Thanks though

 

[2by2zxer]

Re: Not Much Really.....

Sounds to me like the thermotime switch is not opening right away as the tempature increases causing the cold start valve solenoid to stay open allowing too much fuel causing it idle eratically.Try using a jumper on the thermotime plug wiring when engine is cold and have a friend start the car,as soon as it gets to idle speed disconnect the jumper on the thermotime plug.That is the thermotime switch's only function is to active the cold start valve in the event of a cold outdoor ambient tempature and should only close the circuit for a very short period of time,hope this helps.

 

[johnh240]

Why don't you humor me....

and swap the thermotime connector and the coolant temp sensor connector. I know you said you checked the whole thing but this has been the problem on other peoples cars. It won't take but a couple of minutes and if I'm wrong, I'm wrong. It won't hurt anything and it could realistically be the problem. You know the old saying, when you've eliminated all other options, the one that is remaining no matter how illogical it may have seemed, is the answer.

 

[john cross]

Re: Why don't you humor me....

Interesting point and well stated. I have done stupider things...