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chaseincats

Sudden no-spark situation

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Hi guys,

While taking the car out today, everything was running great until I went to wide-open throttle.  After about 20 feet, the car flat out died and refused to start.  The car was low on gas, so after pushing it to a gas station and refilling it, it started right up 3x in a row and was able to drive it home.  I just went down to try and start it and it is now dead.

I pulled the coil wire off of the distributor cap and grounded it against the body - and it seems I am not getting any spark now.  I used a multimeter to poke the 2 coil poles and got less than 1.8ohms so according to the FSM it means the coil isn't bad.

Any ideas as to where I should start to look?  It seems like this is the result of an electrical part that was on its last legs or something...

 

EDIT: I just checked for continuity at the end of the two pick-up coil wires (in the black box where they are bolted to the harness) and did not get continuity.  Could that be the issue?

Box on the right is what I'm referring to: https://www.classiczcars.com/uploads/monthly_2017_02/Screenshot_2017-02-21-14-44-04.png.07517510cbd3dcbe526420d18fa8092e.png

 

-chase

Edited by chaseincats

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35 minutes ago, chaseincats said:

EDIT: I just checked for continuity at the end of the two pick-up coil wires (in the black box where they are bolted to the harness) and did not get continuity.  Could that be the issue?

Could be.  Supposed to be continuity and a certain resistance.  It's in Engine Electrical and the "Bible".  

The breaker plate moves the wires to the pickup coil and sometimes they fatigue and break or short out.

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7 hours ago, Zed Head said:

Could be.  Supposed to be continuity and a certain resistance.  It's in Engine Electrical and the "Bible".  

The breaker plate moves the wires to the pickup coil and sometimes they fatigue and break or short out.

Update: I removed the distributor cap and the front of the pickup coil seems to be scratched, (almost like its been rubbing on the rotating portion of the distributor) there are also very small metal shavings magnetized to the back of the pickup coil.

I tried to shake the main shaft around and it can be moved somewhat but is still very much connected to the engine (not sure if any of this information helps).

Video I just filmed: https://youtu.be/N8R1Ps-r3Pk

Would the pickup coil's outer casing being rubbed against ruin the internals?  Also, if that is indeed what happened, it would probably be a good idea to purchase a new distributor, correct?

 

-chase

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That looks worn out.   I don't think I've seen one that bad before.  I think that some people have devised ways to repair that bushing surface but it takes some work and proper tools.

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4 minutes ago, Zed Head said:

That looks worn out.   I don't think I've seen one that bad before.  I think that some people have devised ways to repair that bushing surface but it takes some work and proper tools.

Definitely agree but I just don't get how my pickup coil can be dead from that (isn't that block just a huge magnet)?  I checked all of the wiring and there aren't any visible breaks, even under the cap.

Edited by chaseincats

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16 minutes ago, Zed Head said:

Your air gap is uncontrollable.

image.png

Ah, do you mean if I move the coil, continuity should appear if it is the proper distance from the center shaft?

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If you're not getting continuity then a/the wire(s)  in the pickup coil probably broke from the vibration of the reluctor wheel beating on it at high RPM.  There's more than just a magnet in there.

I don't know the construction of the Nissan unit but here's a typical diagram from the interwebs.  Not my forte...

image.png

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19 minutes ago, Zed Head said:

If you're not getting continuity then a/the wire(s)  in the pickup coil probably broke from the vibration of the reluctor wheel beating on it at high RPM.  There's more than just a magnet in there.

I don't know the construction of the Nissan unit but here's a typical diagram from the interwebs.  Not my forte...

image.png

It seems the re-manufactured ones are NLA.  Is there a different distributor that is currently made that is swappable that you know of? 

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ZX distributors.  123 ignition.  Someone probably has a used one.  If it's the bushing in the body that's worn you might just get a body and swap your parts in to it.

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On ‎8‎/‎30‎/‎2020 at 7:44 PM, chaseincats said:

I just checked for continuity at the end of the two pick-up coil wires (in the black box where they are bolted to the harness) and did not get continuity.

Reluctor wheel grinding against the pickup face is never a good thing, but before you convince yourself that the pickup is dead, you need to ditch the "continuity" reading on your meter and use Ohms.

The spec from the FSM is 720 Ohms. I don't know if that's high enough of a resistance that the "continuity" scale on your meter might not pick that up. In other words, the pickup coil could be just fine but resistance of the coil may be high enough that your meter won't consider it a connection (and won't beep on continuity).

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6 minutes ago, Captain Obvious said:

Reluctor wheel grinding against the pickup face is never a good thing, but before you convince yourself that the pickup is dead, you need to ditch the "continuity" reading on your meter and use Ohms.

The spec from the FSM is 720 Ohms. I don't know if that's high enough of a resistance that the "continuity" scale on your meter might not pick that up. In other words, the pickup coil could be just fine but resistance of the coil may be high enough that your meter won't consider it a connection (and won't beep on continuity).

Just headed down to the garage to try that and unfortunately no luck on with the multimeter on any of the resistance settings

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So infinite resistance across the pick-up coil? If that's the case, then it certainly does sound like your pick-up is dead.

Carry on, and sorry for the distraction!     LOL  

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13 hours ago, Captain Obvious said:

Reluctor wheel grinding against the pickup face is never a good thing, but before you convince yourself that the pickup is dead, you need to ditch the "continuity" reading on your meter and use Ohms.

The spec from the FSM is 720 Ohms. I don't know if that's high enough of a resistance that the "continuity" scale on your meter might not pick that up. In other words, the pickup coil could be just fine but resistance of the coil may be high enough that your meter won't consider it a connection (and won't beep on continuity).

I was wrong, it seems that it's the magnet peeking through and not the coil being ground down:

unnamed.jpg

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That exposure is normal, but the wear on it is not.  It's the pole of the magnet, the piece that the coil is wound around, I think.  Don't forget that the grinding of the wheel on that piece will cause heat too.

But, overall, if you got no continuity, you got no sine wave, and the ignition module won't produce no spark.  It ain't gonna work.

Might as well take the distributor out and disassemble it to see where the wear is.  In a prior thread that I can't find somebody had a worn shaft and we talked about Redi-Sleeves and other ways to fix it.

You might not be able to find a rebuilt unit but there are places that offer rebuild services.  You send yours in and they fix it and send it back.  Look at RockAuto.

OReilly says that they have them

https://www.oreillyauto.com/shop/b/ignition---tune-up-16776/distributor-12503/8c7c95368caf/1978/nissan/280z?q=distributor

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1 minute ago, Zed Head said:

That exposure is normal, but the wear on it is not.  It's the pole of the magnet, the piece that the coil is wound around, I think.  Don't forget that the grinding of the wheel on that piece will cause heat too.

But, overall, if you got no continuity, you got no sine wave, and the ignition module won't produce no spark.  It ain't gonna work.

Might as well take the distributor out and disassemble it to see where the wear is.  In a prior thread that I can't find somebody had a worn shaft and we talked about Redi-Sleeves and other ways to fix it.

You might not be able to find a rebuilt unit but there are places that offer rebuild services.  You send yours in and they fix it and send it back.  Look at RockAuto.

OReilly says that they have them

https://www.oreillyauto.com/shop/b/ignition---tune-up-16776/distributor-12503/8c7c95368caf/1978/nissan/280z?q=distributor

Yep, just got off the phone with them and they have it via special order.  Rockauto has them too for half the price, so I'll probably go with them.

In the meantime, a friend may have a distributor I can use.  I'll grab a new pickup coil and swap it in there and report back in a week or so.

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On 8/31/2020 at 9:40 PM, Captain Obvious said:

So infinite resistance across the pick-up coil? If that's the case, then it certainly does sound like your pick-up is dead.

Carry on, and sorry for the distraction!     LOL  

Update: My friend has a distributor I can have but said when he measured the pickup coil with a multimeter it ready around 760 ohms instead of 720.  Would that still work?

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Should work fine.  I think that Nissan just didn't set a clear tolerance on that 720 number.  Approximately and far is too vague.  Edit - actually they were vague for the ZX's also.  The ZX uses a different type of coil so the spec is different.

image.png

image.png

Edited by Zed Head

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41 minutes ago, Zed Head said:

Should work fine.  I think that Nissan just didn't set a clear tolerance on that 720 number.  Approximately and far is too vague.  Edit - actually they were vague for the ZX's also.  The ZX uses a different type of coil so the spec is different.

image.png

image.png

Gotcha.  I wasn't sure how 'approximately 720 ohm' Datsun was felt comfy with ,haha.

Regarding the new pick-up coil's air gap:  The FSM says anywhere between 0.2 and 0.4mm works.  Does it matter where in that area the pick-up coil sits?  Basically im curious if there is a benefit to getting it closer to the reluctor (0.2mm) compared to 0.4.

Any ideas?

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I use the middle number for ranges like those.  So, 0.3mm.  If there's wear on the shaft or bushing you don't want to be too close.

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11 minutes ago, Zed Head said:

I use the middle number for ranges like those.  So, 0.3mm.  If there's wear on the shaft or bushing you don't want to be too close.

Fair enough, thanks!

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Update: I got a non-wobbly distributor with a pick-up coil that reads 720ish ohms,

Popped it in and the car started right up but seems to be running a bit rich and is idling about 300-400 rpm lower than it had been.  Could that happen if the pick-up coil's air gap is too large?

 

Any ideas as to what could be going on?

Edited by chaseincats

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I have to ask the obvious... There's no guarantee that your new non-wobbly has everything in the exact same position as what you took out.

Did you set the ignition timing back to the same point it was with your old distributor?

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2 hours ago, Captain Obvious said:

I have to ask the obvious... There's no guarantee that your new non-wobbly has everything in the exact same position as what you took out.

Did you set the ignition timing back to the same point it was with your old distributor?

While it isn't 100% in the same area, it is very close (I'll be using a timing light today to get it back to 10 degrees).  That said, regardless of how far forwards or backwards I turn the distributor, I cannot get it back up to the rpm it was before changing distributors.  Would air gap affect this?

 

EDIT: I just checked and the air-gap was definitely larger than it should be - so I adjusted it and will start the car after everyone is awake to test.  But thinking back to yesterday I did notice yesterday that when it was running rich - after installing the new distributor - when I press on the throttle body accelerator connector, there was a noticeable lag between when you hear the engine suck air in from the filter and when the rpms rose.

I'm not sure if this helps diagnose this at all but I figured disclosing that couldn't hurt.

Edited by chaseincats

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Alright so I increased the idle, timed it to 10 degrees, then brought the idle back down to 800.  It’s running so rich now that it burns your eyes when you stand behind it.

this makes no sense at this point.

any ideas?

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