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

[Dave WM]

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.

Edited January 25, 2019 by Dave WM

[Marty Rogan]

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!

[K Koehn]

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 

[Zed Head]

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.

[K Koehn]

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.

[Zed Head]

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

 

[Dave WM]

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.

[K Koehn]

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

[Zed Head]

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/

[K Koehn]

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.

[Zed Head]

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.

[Dave WM]

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.