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Datsun ZX engine dies
Sent to Car Experts February 03 02:10 PM

I have a 1980 Datsun 280ZX that runs very strong and smoothly - except for one frustrating thing: It starts easily and quickly then idles or runs well during the initial warmup period but, within the first 5 minutes (driving or idling) the engine dies. If I am driving, the fix is to turn the ignition switch to off and then back on - the engine then immediately begins running again very smoothly. Usually, this is a one-time occurrence and, once the engine is hot, it doesn’t happen again. This happens 90% of the time and occasionally the engine will die and then re-catch before I can do the "off-on" thing.
I’ve replaced the ignition switch and related harness and also replaced the fuel pump - both for other reasons, but done with the hope that this other problem would go away. it hasn’t
Help!!
Customer (name blocked for privacy)@hotmail.com (Bill)

Customer (name blocked for privacy)
Status:  Closed   Value: $10
Answer
February 4 12:11 PM (22 hours and 1 minute and 25 seconds later)
         
REPLIEDCheck Mark
  Hello,
 The problem you are having could be a combination of things. I hope this doesn't get confusing.
The engine has a cold start injector on it. It will inject fuel directly into the intake manifold during starting.
 Then there is an altitude compensator.
A throttle position switch or sensor.
Also a fuel pressure regulator.
 A thermo time switch and an air flow meter.
 If the coolant in the car is below around 55°F. then the cold start injector opens to allow extra fuel so the engine will stay running.
 When the car reaches a warmer temperature  then the cold start injector switches off. If there is a fault in this part of the system, say between the throttle position sensor and the cold start valve.
 The computer may not catch it quick enough to stop the dying problem.
   Another problem might be in the air flow meter.
It may have a problem or the computer may not be responding quick enough during this period of warm up.
  This problem requires some time and the proper test equipment to figure out.
Make sure all connections and ground wires are in place and snug.
If you do your own work you will need a book that has test for fuel delivery and air induction.
Otherwise, you will probably have to let someone check it out.
Good luck to you.

  
 
 

Bob Fox
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bfox4546 -- Auto Service Technician -- 100% Positive Feedback on 29 Car Accepts
10 years experience.
Reply
February 4 3:09 PM (2 hours and 58 minutes and 21 seconds later)
         
Reply to bfox4546's Post: Thanks for the response.
The characteristics of the problem lead me to believe that it is electrical in nature, because of the way that it responds. It is either 100% running or is 100% off, with no ramp up or ramp down in engine performance. It can happen at idle or under hard acceleration at 3000+ rpm with the same instantaneous off-on reaction.
I've had a couple of mechanics look at it but, because it is such an intermittent occurrence and doesn't stay "off" for diagnosing, they sorta waved their hands in the air and said "sorry".
On the electrical side of things, are there any particular ground wires that warrant attention?

Thanks
Bill
Customer (name blocked for privacy)
Answer
February 4 4:07 PM (57 minutes and 53 seconds later)
         
ACCEPTEDCheck Mark
  I think I would just take a good look at places where the grounds are attached. The clusters of grounds where their is more than one. Look under the fuse/relay box outside. Check the fenders and look under the dash on both ends and in the middle.
I'm wondering what the system is switching on or off at the second the car dies. Actually this should happen like when the system goes from open to closed loop operation. I would take a look at maybe unhooking the thermo switch while the car is warming up. If you get a check engine light, the older models will clear by pulling a battery cable off for a minute.
   I can't tell you exactly where to start trouble shooting.
If you can find a book on your car at the part store it may help you out a bunch. (may not either)
Stay with it.
 

Bob Fox
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bfox4546 -- Auto Service Technician -- 100% Positive Feedback on 29 Car Accepts
10 years experience.
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