[SOLVED] D21 Z24I to KA24e conversion, and other rambling

[datzenmike]

That's an '85-up 2wd  Z24 distributor. It's also listed as HD and there is a Heavy Duty option that shares some common equipment with the Cab/Chassis and Dual wheel.

[wayno]

Yes that distributor came off an 86 Nissan 720 cab/chassis dually truck, I thought that is what I took it off of, but I have another one from a 1981 Datsun 510 with a Z20s block somewhere and I was not positive that it wasn't from that one, that is why I posted a photo of the numbers on the side of the distributor, I was pretty sure you(Dmike) would figure out which one it was from them numbers.

 

Edited January 7, 2019 by wayno

[datzenmike]

Yes. It has 4 wires, power, two grounds for the coils and a signal wire to shut off one coil under heavy throttle. (I think the white one)

 

In single plug mode, the timing automatically advances to make up for the loss of the shorter burn time so performance is not compromised. The white wire is grounded (or maybe un-grounded) by a manifold vacuum switch.

[wayno]

So you would agree this distributor can be used on a Z24 with a Weber carb?

[datzenmike]

Yes.

[lovot]

Chassis ground functions as the negative for the distributor, red is positive, and can go straight to the battery when the ignition is on (what size fuse should it get?) blue and black with a stripe go to the coils, white should go to a vacuum switch. vacuum advance goes directly to one of the vacuum ports on the intake.

 

is there any way to check if it's wired up right, and working on the bench?

[lovot]

Trying to make sure I'm doing it right, as my truck lost ignition today, so i would like to have it wired in correctly, and not blow it up.

[wayno]

I do not know about the Z24i wiring harness, but the Z24 harness has a ground near the carb, if that wire is not grounded only one of the coils works and it idles roughly.

If I had a wiring diagram for the 720/Z24 I would help you, but all I have is the diesel 720 wiring diagram, it doesn't have any of the distributor stuff in it.

[lovot]

it should be almost exactly the same, except with one more wire to go with the one more coil. Should.

Not sure about the ground near the carb, i would go check, but I had to leave the truck.

[lovot]

distributor has the pins the wires connect to, they read E, B, C,  I, which are wired to blue, black with white stripe, white, and red.

 

The distributor cap references E and I as coil 1, and 2 should those pins be wired direct to the input on the two coils? Blue and Red are also thicker than the other two wires.

 

the white wire shuts off the second coil under heavy load for dumb reasons, so I can simply not connect it.

 

pin B has to be power since it's the only one left, and I assume it's positive because there's an external ground pin (which is just another chassis ground), and the chassis is grounded to the engine.

 

datzenmike: since I assume this thing can be destroyed by plugging it in wrong, I don't want to try hooking it up without your input on this.

[datzenmike]

I think if wired wrong it just does not work. Without power on the correct plug it can't turn on. The white (or maybe yellowish cream from age) wire turns off the exhaust side plugs under heavy load. Nissan says... ' to reduce engine noise under heavy load conditions' ... I think this may be the two flame fronts colliding and could be mistaken for spark knock or ping. If it's truly just noise it really doesn't matter much. Earlier engines didn't have this. Another interesting thing about the dual plugs and the shut off is the timing. Single plugs need a more advanced timing to get all the fuel burned in the short time available. Dual plugs (with 2 ignition sources) take less time so the timing advance is shortened. When switching to single operation the module automatically advances the timing to compensate. Don't ask me how???

[lovot]

I read some of your previous posts on it, but they didn't have the instructions on how to actually wire it from scratch. If hooking it up wrong isn't going to destroy it, then I'll experiment a bit. I'll post how I hooked it up if I get it working.

[wayno]

All I have is a 1984 wiring diagram for the 720, there is a brown wire that appears to be hot to one of the coils, this wire appears to come straight from the ign switch without going thru the fuse block, this wire also is connected to a condenser, there is a BW wire also connected to the condenser that goes to the other coil from the fuse block(controlled by ign switch), there are 2 wires which are R(red) and WL(white/blue stripe), the R wire and the goes to the coil with the BW wire connected to it, and the WL wire goes to the coil with the Br wire connected to it.

There are other wires showing to be connected to the distributor, a B wire going to the condenser, and a W wire going to a vacuum switch although this wire might only be on the MPG option.

 

As I mentioned, this info is from a 1984 Nissan service manual, that distributor came from a 1986 Nissan 720 cab/chassis dually model.

[datzenmike]

The intake coil is wired directly from the ignition's fusible link. The exhaust side comes from the ignition also but goes through the fuse box. First fuse on the left side.

 

wayno every Z24 wiring diagram seems to have different colors to and from the coils and the distributor modules... I can't say with any certainty which is which.

 

 

The MPG option has a knock sensor and a circuit for this and an ignition retard to auto adjust the timing below the knock threshold. Remember the vacuum switch that shuts off the exhaust side plugs under load? When this is activated the timing is automatically advanced to compensate for single plug operation. Maybe the two are sort of one and the same.

[wayno]

I described what I was looking at in a 1984 Nissan 720 service manual, it baffled me how power to each coil came from the ign, but one went thru the fuse block while the other did not go thru the fuse block, but they both came from the same ign wire.

Yes the WB wire going to the ignition comes from the fusible links, this wire comes out of the ign as WL, when it splits before the fuse block the wire that bypasses the fuse block becomes Br(brown), the other that goes thru the fuse block becomes BW.

I was concentrating on the coils and distributor and where the 2 wires that power the distributor/coils come from, the Br(brown) wire appears to power the distributor and one coil, the BW wire appears to power the other coil, both these wires share the same condenser.

It's a stupid complicated setup, but I only use 2 types of 720 harnesses, the 1980 harness with one coil, and the early diesel harnesses, I do have one 85 diesel harness but it is different, I will likely never use that harness.

 

If I had a way to scan this wiring diagram I would have and then posted it.

Edited January 19, 2019 by wayno

[Lockleaf]

I've had 4 84+ 720s.  All had the wiring for the condenser, but none have ever had a condenser in them.  Not sure why that is.

[datzenmike]

The one I have is ratty. I spent an hour looking through the local Nissan dealer's upstairs archive of FSM about 20 years ago, and no he wouldn't let me have them but aI made several copies. One for an '83 diesel. Doesn't have the year on it and it might be for a Z22? I have a partial diagram in my '84 FSM but it doesn't show each wire. Rather a simplified depiction of a schematic with boxes representing major electrical parts. . It's no help whatever.    .

[lovot]

Did some experimenting:

 

Pin B definitely goes to positive, probably through the ignition relay

E and I go to the coil neg

C is disconnected.

 

I believe wiring the positives for the distributor and coils to the ignition relay would work just fine, or to a simple toggle switch.

 

Used a 12V LED lamp and a random battery to test if the distributor worked, and it did, light would flash every time the distributor tried to fire. I noticed that the ignition coils on my truck have the driver circuitry strapped directly to them with a couple short wires between the driver and coil, the coils also look non-standard to me. I figured 2 standard coils would be more likely to work than attempting to rig the stock coils directly to the distributor, so I purchased 2 standard ignition coils, and the current limiting resistors to match (not sure what they were supposed to go on, but they all work exactly the same way, so I doubt it matters, cylinder with 3 wires, +, -, and the HV output, not rocket surgery). I have the distributor and coils wired up on the bench right now with a piece of wire as a spark gap between the output and negative terminal on the coils, they fire exactly like the should as far as I can tell.

 

I believe wiring the positives for the distributor and coils to the ignition relay would work just fine, or to a toggle switch.

 

Also got the low pressure lift pump for the carb, after dealing with the ignition system, I'm going to try for the carb.

[wayno]

I hooked up and installed everything so I can now scan stuff, this is what I was describing out of the 1984 service manual.

[lovot]

Doesn't look like they labeled the wires very well, could also be the compression artifacts obfuscating the letters.

 

In any case, I seem to have it figured out, I could draw up a wiring diagram if someone wants it, just know that my drawing abilities are limited.

 

Thanks for the help, wouldn't have had a distributor, or a starting point for the wiring without it.

[wayno]

It is what it is, every wire has letters for the color, it's just a mini harness diagram of that circuit, why they did some stuff is over my head, I see no reason for one coil to be routed thru the fuse block and the other one to completely bypass it when the power comes from the same place.

 

[lovot]

and the coils do the exact same thing, it's sort of bizarre.

[lovot]

distributor shaft is different, same length, but the older style is an offset slot drive with a plastic collar and a metal spring clip to keep the slot centered, new style is a half moon shaft with a steel spline collar. It LOOKS like I can drive out the roll pins that retain the collars, and swap them, over the weekend I'm going to have to see if one of the sides of the slot drive are the same size as the half moon on the new one, if so I can grind off the other side of the slot drive, and it should key up.

[datzenmike]

On 1/19/2019 at 7:12 PM, lovot said:

and the coils do the exact same thing, it's sort of bizarre.

 

Not really. Twin plugs mean there are two ignition sources and like lighting a candle at both ends it burns up faster. If the burn time is shortened you don't need as much ignition advance. 3 degrees compared to the L20B's 12 degrees. This would lessen the time the insides of the combustion chamber have to absorb heat and cool (quench) the combustion and more heat is available to do work like pushing down on the piston. Less heat absorbed means less chance of pre ignition.    

 

 

 

 

 

11 minutes ago, lovot said:

distributor shaft is different, same length, but the older style is an offset slot drive with a plastic collar and a metal spring clip to keep the slot centered, new style is a half moon shaft with a steel spline collar. It LOOKS like I can drive out the roll pins that retain the collars, and swap them, over the weekend I'm going to have to see if one of the sides of the slot drive are the same size as the half moon on the new one, if so I can grind off the other side of the slot drive, and it should key up.

 

The Z24i in the late 720 and early D21uses a splined CAS crank angle sensor. The spline removes rotational chatter from the shaft making the timing extremely stable compared to the earlier 'blade and slot' set up..

[lovot]

According to the schematic, one coil is wired through a 10A fuse to the ignition switch, while the other is wired direct to the ignition switch, both coils do exactly the same thing, so it's odd that the wiring would be different in any way.

 

spline is definitely better than a slot drive, which is one reason why I'm trying to switch the distributor over to spline instead of trying to find an old style timing shaft, just have to pull the distributor and get the collars off to see if an angle grinder can adapt the old style to the new style.