1980 280zx cold start issue? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 8 (permalink) Old 06-15-2019, 07:54 PM Thread Starter
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1980 280zx cold start issue?

I have a 1980 280zx, The car has 112K miles on it. When I go to start the car, it takes 2-3 key cranks to get it to fire up but then it runs perfect. It actually runs really good. I read in my service manual that there is a process that happens when a car is cold where it injects some fuel into the air intake when the water temp sensor indicates that the car is cold. It's summer here now so nothing should be really cold. Can anyone suggest what I need to do to make this car fire up on the first key turn? If I hit the gas pedal during the cranking process it doesn't help. I feel there are a couple sensors that I need to change to make the car start instantly. PS: I'm loving working on these cars!!!
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post #2 of 8 (permalink) Old 06-16-2019, 05:29 PM
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Originally Posted by cetacea View Post
I have a 1980 280zx, The car has 112K miles on it. When I go to start the car, it takes 2-3 key cranks to get it to fire up but then it runs perfect. It actually runs really good. I read in my service manual that there is a process that happens when a car is cold where it injects some fuel into the air intake when the water temp sensor indicates that the car is cold. It's summer here now so nothing should be really cold. Can anyone suggest what I need to do to make this car fire up on the first key turn? If I hit the gas pedal during the cranking process it doesn't help. I feel there are a couple sensors that I need to change to make the car start instantly. PS: I'm loving working on these cars!!!
A couple of things. First off, the car starting on 2-3 cranks is fine especially when cold and better than most of our cars. The 280zx has a fuel injected engine. So unlike carbs, tapping the throttle when starting it doesn't add any extra gas - it just opens and closes the throttle body which does nothing during starting.

Regarding the extra fuel into the air intake, there is what's called the "cold start valve." It is essentially the 7th fuel injector and it sits right after the throttle-body in the intake manifold. It only fires when the coolant is below 50 degrees (I think).

Try looking for vacuum leaks but other than that, your engine is in great shape and with the car starting on 3 cranks when cold you probably won't have any...

1978 280z - stock L28 engine - Dallas, TX
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post #3 of 8 (permalink) Old 06-17-2019, 08:22 AM
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could be this
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post #4 of 8 (permalink) Old 06-17-2019, 08:27 AM
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with regards to fuel pressure and cold starting.


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post #5 of 8 (permalink) Old 06-20-2019, 08:52 PM Thread Starter
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A couple of things. First off, the car starting on 2-3 cranks is fine especially when cold and better than most of our cars. The 280zx has a fuel injected engine. So unlike carbs, tapping the throttle when starting it doesn't add any extra gas - it just opens and closes the throttle body which does nothing during starting.

Regarding the extra fuel into the air intake, there is what's called the "cold start valve." It is essentially the 7th fuel injector and it sits right after the throttle-body in the intake manifold. It only fires when the coolant is below 50 degrees (I think).

Try looking for vacuum leaks but other than that, your engine is in great shape and with the car starting on 3 cranks when cold you probably won't have any...


Thanks! I think the video below might be the issue except that the motor always starts after about the 2nd or 3rd crank. I define a crank as : turn the key....and you get about 4 or 5 revolutions from the starter.. Of course the other day when it was 80 degrees it fired up upon turning the key. I'll keep working on this as I know this baby should start instantly. Thank you very much for you help. I love these cars.
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post #6 of 8 (permalink) Old 06-24-2019, 07:45 PM
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Originally Posted by cetacea View Post
Thanks! I think the video below might be the issue except that the motor always starts after about the 2nd or 3rd crank. I define a crank as : turn the key....and you get about 4 or 5 revolutions from the starter.. Of course the other day when it was 80 degrees it fired up upon turning the key. I'll keep working on this as I know this baby should start instantly. Thank you very much for you help. I love these cars.
Gotcha - you've got the wrong definition of a crank then - that's whats throwing us off. You're talking about 2-3 'keyturns' a crank is the "4 or 5 revolutions from the starter."

So in that case I agree with Dave, it's most likely the ignition switch in the back of the tumbler.

1978 280z - stock L28 engine - Dallas, TX
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post #7 of 8 (permalink) Old 06-26-2019, 08:35 PM
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Originally Posted by cetacea View Post
Thanks! I think the video below might be the issue except that the motor always starts after about the 2nd or 3rd crank. I define a crank as : turn the key....and you get about 4 or 5 revolutions from the starter.. Of course the other day when it was 80 degrees it fired up upon turning the key. I'll keep working on this as I know this baby should start instantly. Thank you very much for you help. I love these cars.

chasincats, you need to re-read cetacea's post he said that crank = turn the key.....and get 4 or 5 revolutions from the starter. He's got it correct in fact. oops
First check your plug gap, then you need to check your fuel pressure. Start the car, let it run for a few minutes, then shut the engine off. Check the gauge in a few hours, you should have at least 8 lbs of fuel. Another tip to start the 80 and newer zx's is to turn the key to the run position for 3-5 seconds then turn it to the start position and see how it starts. That short delay in the running position will energize the fuel pump before you actually crank the engine over. Sometimes that can make a lot of difference. If all that looks ok then try doing a valve adjustment cold. Put it at .008 intake and .010 exhaust. Also, pull your coil wire out of the coil and make sure that it's dry inside the coil tower. If it's wet then it's starting to leak oil and replace the unit. If it's dry, then it's probably ok.
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post #8 of 8 (permalink) Old 06-28-2019, 01:47 AM
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chasincats, you need to re-read cetacea's post he said that crank = turn the key.....and get 4 or 5 revolutions from the starter. He's got it correct in fact. oops
First check your plug gap, then you need to check your fuel pressure. Start the car, let it run for a few minutes, then shut the engine off. Check the gauge in a few hours, you should have at least 8 lbs of fuel. Another tip to start the 80 and newer zx's is to turn the key to the run position for 3-5 seconds then turn it to the start position and see how it starts. That short delay in the running position will energize the fuel pump before you actually crank the engine over. Sometimes that can make a lot of difference. If all that looks ok then try doing a valve adjustment cold. Put it at .008 intake and .010 exhaust. Also, pull your coil wire out of the coil and make sure that it's dry inside the coil tower. If it's wet then it's starting to leak oil and replace the unit. If it's dry, then it's probably ok.
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My point was that is not how the term 'crank' is used - which gave me the wrong idea as to what is going on.

1978 280z - stock L28 engine - Dallas, TX
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