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K Koehn

My 280Z cranks but doesn't stay running once started

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First off, I don't know much about 280Z's as I have only owned 240Z's.  But this sounds like a problem I had with my first 240Z.  It had been running fine.  Then one day, I could turn the key, it would crank and fire, then die.  I realized that as soon as I let go of the key from the start position it would die.  If I held the key, it would continue to run.  It turned out the be the ballast resister going bad.  Once I replaced that, it was back to normal.

If the 280Z has a ballast resistor, I would replace that and see what happens.  

Good luck!

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44 minutes ago, Dave WM said:

The only time I had on just die out right like that, was when the ECU acted up. I put a backup in it and it worked fine. I then put the orig back in and it too worked fine. could be the electronic flaking out, generally whacking it is a 1st try (just slap the case of the ecu with it installed with your hand) at a fast fix if you are stuck somewhere. Fuse links would be suspect next since you may have an intermittent short that could have take one out. Lastly grounds can corrode esp around water. You may want to just check all those a well. This all assumes the injectors are NOT firing TBD by you later with the listening approach. The intermittent cutting out sounds electrical in nature, but could be a fuel starving issue. On my car hard left turns on low fuel will cause the car to stumble, I presume the fuel is sloshing away from the pickup. Thing about FI cars vs Carb cars, no float bowl to keep a bit of fuel on hand. So with FI any interruption will result in problems. So if the injectors don't fire (ECU) or the pump stumbles (relay) or the fuel supply to the pump is compromised (fuel slosh) you will have problems. Oh and I forgot the time I just ran out of gas... fuel indicator was not accurate.

Thats one thing I've always been afraid of, is that fuel indicator being wrong, but ill definitely keep all of that in mind, helps alot. I also wondered about my fuse links, I saw on the case of those links, one says BATT (Black) Ign (Green) but mine have a green and red fuse link, could this be an issue 

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37 minutes ago, Marty Rogan said:

First off, I don't know much about 280Z's as I have only owned 240Z's.  But this sounds like a problem I had with my first 240Z.  It had been running fine.  Then one day, I could turn the key, it would crank and fire, then die.  I realized that as soon as I let go of the key from the start position it would die.  If I held the key, it would continue to run.  It turned out the be the ballast resister going bad.  Once I replaced that, it was back to normal.

If the 280Z has a ballast resistor, I would replace that and see what happens.  

Good luck!

This is a good one.  Checking voltage at the coil with the key on would show that.

This story has gone the typical route of 280Z EFI problems.  Try the quick fixes, poke here, pull there, but in the end the OP needs to get a volt meter or test light and check the basics.  No meter, slow progress.

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39 minutes ago, Marty Rogan said:

First off, I don't know much about 280Z's as I have only owned 240Z's.  But this sounds like a problem I had with my first 240Z.  It had been running fine.  Then one day, I could turn the key, it would crank and fire, then die.  I realized that as soon as I let go of the key from the start position it would die.  If I held the key, it would continue to run.  It turned out the be the ballast resister going bad.  Once I replaced that, it was back to normal.

If the 280Z has a ballast resistor, I would replace that and see what happens.  

Good luck!

ill try that out if the other possibilities fail. Thank you.

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2 minutes ago, K Koehn said:

ill try that out if the other possibilities fail. Thank you.

thats not the best way.  get a meter and do the proper tests in order.  make a list and write the numbers down  dont do pass-fail, real numbers

 

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ZH is dead on. Even if you get lucky and get it going with a lucky guess on our part, ultimately it will fail again, and the only real answer is to become your own EFI expert. Sit down and read the chapter in the book about EFI, then read it again, its really not that hard just wordy. The BCDD is prob the trickiest part of the system as far as testing goes. The rest is very straight forward.

Good luck, hope you get it going with one of the guesses, but please consider the above.

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21 minutes ago, Zed Head said:

thats not the best way.  get a meter and do the proper tests in order.  make a list and write the numbers down  dont do pass-fail, real numbers

 

That helps alot! I really needed that manual, it really explains everything pretty simple, ill do those tests, I just got myself a new multimeter and test light

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Here's a couple more.  Marty Rogan's thought about the ballast resistor fits your problem pretty well.  I'm not sure how deep the EFI manual goes in to the ignition system.  Check the Engine Electrical chapter in the FSM.  1975 has a ballast resistor, it's the white ceramic things with a bunch of wires connected to it, by the coil.

Good luck.  Get good measurements and write them down.  Download a 240Z FSM if you want to learn how to set your points.

https://www.classiczcars.com/files/category/13-280z/

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2 hours ago, Zed Head said:

Here's a couple more.  Marty Rogan's thought about the ballast resistor fits your problem pretty well.  I'm not sure how deep the EFI manual goes in to the ignition system.  Check the Engine Electrical chapter in the FSM.  1975 has a ballast resistor, it's the white ceramic things with a bunch of wires connected to it, by the coil.

Good luck.  Get good measurements and write them down.  Download a 240Z FSM if you want to learn how to set your points.

https://www.classiczcars.com/files/category/13-280z/

I just went outside to check if I could hear clicking from the injectors just to start off, and now my car won't crank at all, only activates the fuel pump and the fuel regulator hiss in the fuel rail,  but does not even crank over now, so I went over to the battery, it has 13 volts sitting, and 12 volts cranking, and the starter also has 12 volts sitting,and 12 volts even when cranking, should I try and just go for the ballast resistor and coil to start off testing? I didn't mess with anything prior to this just now happening, so its odd to me. Here's a photo of my resistor, the 1st terminal seems to be loose, as if its broken.

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Check the little yellow wire to the starter solenoid.  It might be loose or disconnected.

You're standing right there by the coil with the key on.  Might as well take a measurement.  Sometimes people take the same measurement multiple times.

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resolve one issue at a time, get it cranking again. Start by checking to see if the solenoid on the starter is getting power from the wire that has a push on connector when the key is in the start mode. A test lamp would be a good way to check. BTW make sure the battery cables are clean and well connected. Basic stuff 1st. the problem with volt meters is they apply no load on the circuit under test. Here a test lamp is often a better diagnostic tool.

 

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On 1/25/2019 at 7:00 PM, Zed Head said:

Check the little yellow wire to the starter solenoid.  It might be loose or disconnected.

You're standing right there by the coil with the key on.  Might as well take a measurement.  Sometimes people take the same measurement multiple times.

I checked that wire on the top of the starter and its was on tight, but it looks like my ignition coil is leaking now and the + and - sides aren't reading any voltage across eachother twice and the test light showed no power to that yellow wire going to the starter as well in the on position

Edited by K Koehn

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The yellow wire only gets power when the key is turned to Start.  No power there when the key is on.  No offense, but you need to go through the sequence of how things work.  It will help your troubleshooting efforts.

Sounds like the points might have been closed when the key was on, or the points distributor is wired incorrectly with constant power, and the engine stopped with the points closed.  Looks like you overheated the coil.

Voltage is not measured across + and - , it's measured from + to ground, and - to ground.

You're making progress.  Good luck.

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11 hours ago, Zed Head said:

The yellow wire only gets power when the key is turned to Start.  No power there when the key is on.  No offense, but you need to go through the sequence of how things work.  It will help your troubleshooting efforts.

Sounds like the points might have been closed when the key was on, or the points distributor is wired incorrectly with constant power, and the engine stopped with the points closed.  Looks like you overheated the coil.

Voltage is not measured across + and - , it's measured from + to ground, and - to ground.

You're making progress.  Good luck.

Ok, thank you

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@K Koehn:  Did you resolve this issue?  I'm having the same issue with a '72 Z running carburators.  Mine starts for a second then stops.  I"m getting no spark when I turn with a remote starter, BUT when I start with key, and hold the key on the START position it runs.  Ignition switch issue?  How would I diagnose this?    

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28 minutes ago, Jughead said:

@K Koehn:  Did you resolve this issue?  I'm having the same issue with a '72 Z running carburators.  Mine starts for a second then stops.  I"m getting no spark when I turn with a remote starter, BUT when I start with key, and hold the key on the START position it runs.  Ignition switch issue?  How would I diagnose this?    

Likely suspects include the ballast resistor, tachometer, and ignition switch.

This diagnosis assumes the car to be stock. Put the key in the ON position. Use a voltmeter to measure voltage to ground at each terminal on the ballast resistor. If one side does not have voltage to ground, replace the ballast resistor. If neither side has voltage, the problem is with the module in the back of the ignition switch.

If both sides have voltage, then lift the negative wire off of the coil. Measure voltage to ground on positive side of the coil. If you do not have voltage, the problem is the tachometer. Check to make sure the tachometer is firmly connected to the dash harness.

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Here's an old thread about problems with the ignition switch.  Test at the ballast and coil first like SteveJ says, if there's no power there, work your way back.

 

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@SteveJ:  Thanks for the advice.  I measured the resistor at both sides  No current.  So I swapped the module in the back of the switch with a "new"  module from an old ignition switch that came in a box with the car.  Same result as originally described - no voltage at either resistor terminal and same (non) starting symptoms.  What would you try next?  A new module?

Thanks!

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What do you mean by "no current"? I asked you to check voltage to ground. How do you know the swapped module is good? Could you tell if the key was turning the module?

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Update:  Found a broken female spade connector om wire to resistor.  Renewed it and now I have voltage to resistor....and the car runs nicely...THANKS!!!

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Hello everyone, my apologies for not concluding on this issue, My issue ended up being the EFI control module itself, as well as a short near the ballast resistor. I hope this helps anyone in the future.

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4 minutes ago, K Koehn said:

Hello everyone, my apologies for not concluding on this issue, My issue ended up being the EFI control module itself, as well as a short near the ballast resistor. I hope this helps anyone in the future.

I thought you said it was a 72. That year doesn't have any EFI components. 

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SteveJ  Im the original poster that had the 1975 280Z with the issue of it not staying running

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3 hours ago, K Koehn said:

SteveJ  Im the original poster that had the 1975 280Z with the issue of it not staying running

Got it.

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