Sudden no-spark situation

[Captain Obvious]

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!       

[chaseincats]

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:

[Zed Head]

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

[chaseincats]

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.

[chaseincats]

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!       

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?

[Zed Head]

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.

Edited September 3, 2020 by Zed Head

[chaseincats]

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.

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?

[Zed Head]

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.

[chaseincats]

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!

[chaseincats]

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 September 6, 2020 by chaseincats

[Captain Obvious]

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?

[chaseincats]

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 September 6, 2020 by chaseincats