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TheCrazySwede

Building an L28 (NA)

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Try disconnecting your alternator completely. It may have a big short in it.

If not, disconnect everything wherever you can and measure the battery voltage. Then add things slowly until you get a drain.

The alternator is new. So far, I've tried the stock alternator, a newer alt with internal voltage regulator (did the bypass trick) and now a new alt with external regulator hooked up to a brand new voltage regulator. All produced same results. I'll try to run it without an alt altogether and see what readings I'll get! Haven't tried that yet!

 

  

What I'm seeing after a quick look at the schematic for a Z (I'm new to these but work on electronics for a living) is a couple things.

First, the indication that turning on the lights works but your voltage goes to 0. That indicates that wherever your voltmeter is wired to is seeing ground. I need to know where that tap is.

Second issue is that voltage spike while running. I'm betting that wherever the sense wire goes is shorted to ground. That would cause it to push the alternator high.

A few possibilities from looking at the short issue for a few minutes: bad light switch, bad tail lamp (if removing the bulb fixes the issue that's it), bad dimmer.

I'm going to bet it's two seperate problems.

I get the same symptoms with pretty much every accessory, except for turn signals. At times of short, turning off the car and removing my key brings voltage back, but simply inserting my key into the ignition (without waiting a bit) results in the drop again, even with everything off.

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You should make a sig with year of car and modifications so people know what wiring system you're working with.  Too many pages to try to figure it out.

 

Really though you should just sit down with a wiring diagram and a meter and verify continuity to the positive cable on things that get power and continuity to the negative cable on things that get grounded.  You're just shooting in the dark and blowing holes in things you can't see at this point.  Your new motor deserves the time.

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The alternator is new. So far, I've tried the stock alternator, a newer alt with internal voltage regulator (did the bypass trick) and now a new alt with external regulator hooked up to a brand new voltage regulator. All produced same results. I'll try to run it without an alt altogether and see what readings I'll get! Haven't tried that yet!

 

  

I get the same symptoms with pretty much every accessory, except for turn signals. At times of short, turning off the car and removing my key brings voltage back, but simply inserting my key into the ignition (without waiting a bit) results in the drop again, even with everything off.

 

Man have I spent time fighting the the electric systems.  Good news it's probably solvable! Just takes a lot of time and staring at the schematic! 

 

So are you saying that you have a short that causes your alternator to fry (outputs >14v) and a causes a fusable link to burn? And this happens when you turn on certain things?

 

1. Is it the alt/bat fusable link that goes?

 

2. You are not leaking coolant or something into the alternator? Bad mounts can cause the fan to hit the alternator (have happen to me, twice).

 

3. If you disconnect the alternator, do you still see the voltage drop if you insert the key or turn on something?

 

You could try the following:

1. Remove most of the fuses

2. turn stuff on/off and check for the drop

3. If no drop then but in another fuse and goto 2 until you get the drop.

 

I think you need to isolate the circuts more. There is a ALOT of wiring to all kinds of stuff. 

 

You could try and remove all the fuses (not the fusable links) but the correct fuses. 

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Ok, if you have an issue when you insert but don't turn the key your ignition switch is likely bad. It's not supposed to do ANYTHING with just a key in it according to everything I can find. If it's internally crosswiring you will get some odd results, which you have.

 

Also, those other questions are important. Year, model, where the sense wire is going, and where the voltmeter is bridged at.

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I think that I just read some posts about a "key in ignition" buzzer,and the associated wiring at the ignition column.  Somebody started one of those "where do these wires go" threads.  It's recent, maybe this forum, maybe zcar.com.  If that loose wire end was shorted, who knows.

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Man have I spent time fighting the the electric systems.  Good news it's probably solvable! Just takes a lot of time and staring at the schematic! 

 

So are you saying that you have a short that causes your alternator to fry (outputs >14v) and a causes a fusable link to burn? And this happens when you turn on certain things?

 

1. Is it the alt/bat fusable link that goes?

 

2. You are not leaking coolant or something into the alternator? Bad mounts can cause the fan to hit the alternator (have happen to me, twice).

 

3. If you disconnect the alternator, do you still see the voltage drop if you insert the key or turn on something?

 

You could try the following:

1. Remove most of the fuses

2. turn stuff on/off and check for the drop

3. If no drop then but in another fuse and goto 2 until you get the drop.

 

I think you need to isolate the circuts more. There is a ALOT of wiring to all kinds of stuff. 

 

You could try and remove all the fuses (not the fusable links) but the correct fuses. 

 

1. Yup

2. Nope - nothing disturbing alt from what I can see

3. Haven't tried running without alt yet. Will try this and report back!

 

 

Ok, if you have an issue when you insert but don't turn the key your ignition switch is likely bad. It's not supposed to do ANYTHING with just a key in it according to everything I can find. If it's internally crosswiring you will get some odd results, which you have.

 

Also, those other questions are important. Year, model, where the sense wire is going, and where the voltmeter is bridged at.

 

1977 280z

The stock motor had 0 issues. These problems appeared the moment I did the engine swap. That's why I thought I might have had an improper ground - but I can't find any.

 

It's on zcar.com, called "1976 280z wiring problems".  Post #7.

 

You know what, the other day my "door open, key in ignition" chime was sounding reaaaally funny. I just assumed it had something to do with the 16v+ being pumped out. But yeah, the voltage drop issue does sometimes appear when just inserting my key into the ignition - sometimes not. Usually it appears if I cause the volt drop, the turn off the car and remove the key and NOT WAIT long enough before putting my key back into the ignition. If I wait like 2-3 minutes, it usually doesn't do it, but if I insert the key immediately after having removed it (and doing something that causes the volt drop) the voltage drops again, even with no accessories on. Eventually comes back up again. Really weird. I haven't dug into much behind the dash yet. Maybe that's where my problem lies. 

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I think you need to start removing fuses and start to isolate the problem. If you notice that you don't see the problem when fuse X is removed then that is a good start.

This works, but note that the circuit that's under discussion as the possible problem likely isn't fused (most key buzzers aren't). You'd never find the problem that way if this IS the problem. 

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Quick update:

 

Bought a new harness and I'm going to strip the car down and re-do all the wiring. Figure I'm going to want to do that anyway. Hoping I find something along the way.

 

Here's the sound of the car with the carbs better tuned (Getting a hang of it!)

 

Edited by TheCrazySwede

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Do you have a really quiet exhaust installed?

 

I don't know if it's just me, but I've never heard an NA L28 that sounds like that. Almost sounds like it's not running right.

 

Not really quiet, but not shouting by any means. It's a custom made Abarth exhaust tailored for my Z. It sounds a bit odd because of the way it was recorded + the way YouTube handles audio. Also helps if you have good speakers hooked up! (A laptop doesn't do it justice.) It sounds much, much deeper in person.

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Do you have a really quiet exhaust installed?

 

I don't know if it's just me, but I've never heard an NA L28 that sounds like that. Almost sounds like it's not running right.

 

 

Kind of sounds like it's running on 5 cylinders - I know the sound well since I foul plugs pretty often.  Could be the recording/youtube though. 

 

You, gentlemen, are Wizards. 

 

After reading both your replies over, it grew on me that something wasn't running right.

 

You guys are on a Sage level of Z Ownership - found out I was running on 4cyl when idling!

No change in idle if I disconnect Cyl4 and Cyl5. I tested both cylinders for spark and got it - compression test comes out good.

Adjusting the idle mixture screws, however, don't do anything. These are two different screws on two different carbs. I can hear the engine acting differently if I adjust every other idle mixture, but the ones over Cyl4 and 5 show no difference.

 

Now underload (perhaps when the main circuits kick in?) the car pulls hard and sounds like it runs on all six.

 

Anyone have any ideas what's going on? Perhaps mixture screws got something stuck at the bottom?

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You, gentlemen, are Wizards. 

 

After reading both your replies over, it grew on me that something wasn't running right.

 

You guys are on a Sage level of Z Ownership - found out I was running on 4cyl when idling!

No change in idle if I disconnect Cyl4 and Cyl5. I tested both cylinders for spark and got it - compression test comes out good.

Adjusting the idle mixture screws, however, don't do anything. These are two different screws on two different carbs. I can hear the engine acting differently if I adjust every other idle mixture, but the ones over Cyl4 and 5 show no difference.

 

Now underload (perhaps when the main circuits kick in?) the car pulls hard and sounds like it runs on all six.

 

Anyone have any ideas what's going on? Perhaps mixture screws got something stuck at the bottom?

 

You sure you don't have #4 and #5 plug wires mixed up?

 

Otherwise, I'd check the condition of your idle jets for those cylinders. Could be a clog in the jet or passage. Clean with solvent and compressed air.

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You sure you don't have #4 and #5 plug wires mixed up?

 

Otherwise, I'd check the condition of your idle jets for those cylinders. Could be a clog in the jet or passage. Clean with solvent and compressed air.

 

Wires are correct. I checked the idle jets and passage - used compressed air just in case. No change. 

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Take out your mixture screws and see if that orifice is blocked. If you're definitely getting fuel and it runs on all 6 on the mains, then it certainly sounds like something going on with the idle circuits for those cylinders.

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Take out your mixture screws and see if that orifice is blocked. If you're definitely getting fuel and it runs on all 6 on the mains, then it certainly sounds like something going on with the idle circuits for those cylinders.

 

I checked those and nothing seems blocked. Even swapped them with ones from running cylinders and got nothing. This is really odd...

I read online that someone screwed the mixture screws in too tight once and something got stuck so it didn't back out when he started richening them. I highly, highly doubt that's my issue, cause these are brand new carbs and I've been very gentle with pretty much everything.

 

I'm gonna head back to the spark issue again. I tested spark from the wires straight from the dizzy, but I only visually inspected each plug. I didn't swap plugs (or can't remember if I did) or replace them or anything like that. I got some spare ones laying around. I'll replace those plugs with new ones and try again. Doesn't hurt to try.

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It's a hassle, but swapping around the carbs to see if the problem moves with them is useful to see the problem is carb related or not.

 

If it is, it's going to be a little work to sort out. Lots of trial and error.

 

One of my Mikunis was misbehaving once, same issue as you - fine on heavy throttle, but not firing at idle. I tried to be methodical in my approach and nothing worked. What did work was stripping the carb to the body, submerging it in water, then blowing air from a compressor through each passage. The thought here being that the water in the passages will grab more detritus while being blown out. In this case I rebuilt the carb afterwards and it worked perfectly. Presumably some dirt was blocking one of the pilot jet passages.

 

Good luck!

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It's a hassle, but swapping around the carbs to see if the problem moves with them is useful to see the problem is carb related or not.

 

If it is, it's going to be a little work to sort out. Lots of trial and error.

 

One of my Mikunis was misbehaving once, same issue as you - fine on heavy throttle, but not firing at idle. I tried to be methodical in my approach and nothing worked. What did work was stripping the carb to the body, submerging it in water, then blowing air from a compressor through each passage. The thought here being that the water in the passages will grab more detritus while being blown out. In this case I rebuilt the carb afterwards and it worked perfectly. Presumably some dirt was blocking one of the pilot jet passages.

 

Good luck!

 

I fear perhaps I might have to go down this route. i also don't have filters on my carbs yet - could dirt and crap have gotten in and clogged some bits up? Thanks for the advice!

 

I feel like I'm always taking two steps forward and one step back, haha

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I fear perhaps I might have to go down this route. i also don't have filters on my carbs yet - could dirt and crap have gotten in and clogged some bits up? Thanks for the advice!

 

I feel like I'm always taking two steps forward and one step back, haha

At lest you have 66% of your engine running, mine is at 0%.

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