Wiring harness help

[None_zero]

That can't be normal right I've never seen the timing skipping like that 

 

[datzenmike]

Thought I could avoid the long story.

 

 

OK combustion does not happen instantly, it takes a small amount of time to burn and the hot gasses expand. The proper ignition timing starts the burn just prior to TDC so that there is time for the combustion process to reach maximum cylinder pressure at around 17 degrees after TDC. Any less and the crank, rod and piston are almost stacked in a straight line and the pressure isn't transferred into motion efficiently. Any more than 17 degrees and the piston is rapidly accelerating away and the pressure expands into an increasingly empty cylinder.

 

On a single plug engine the advance required is the longest and all manner of bad things happen. There is more time for heat energy to transfer into the top of the cylinder, combustion chamber and the piston top. The more heat transferred the less is available for expansion and pushing the piston down. More time for detonation or pre ignition to happen from the hotter combustion chamber. Also more time to form oxides of nitrogen, but we don't care about that. By having two ignition sources the burn time is drastically shortened so the timing is lowered from over 10 to about 5 degrees BTDC to properly hit that sweet spot of 17 degrees ATDC. Less pinging, less heat loss (more efficient) less nitrogen oxide produced.

 

I left out some information when I said that the distributor only switched to single plug by turning off the exhaust side. The module also automatically advances the timing because....... longer burn time with single plug. If you didn't, power would drop off.

 

Nissan's reason for single plug operation under heavy load conditions is " to reduce engine noise." I suspect that the 'noise' is simply the two flame fronts colliding and it sounds like a diesel or something.

 

So now you have the entire story.

[None_zero]

So just an update, after many adjustments and fixes the list of which im sure to forget half at least, includes such things as, replacing two missing bolts from the exhaust manifold, rearranging and replacing some of the vac hoses advancing the timing as far as it will allow (this did more than any other single thing I believe) redoing the ground connections to block and body as I mentioned before, the list goes on but finally the old girl is on the road again and consuming a reasonable amount of fuel, today oddly the spark wire from the dizzy to the intake ignition coil ejected itself and was arcing against the body when I left work, some burn marks near the top of the coil and the inner metal sleeve looked well corroded, some how the spark wire was pulled back through the boot so far it was jammed into the side of the boot instead of angling down toward the opening. I'm assuming it needs a longer wire and the engine motion pulled it through little by little. But I still am having trouble with this damn wiring. Everytime I think I've finally gotten it I have simply replaced one problem with another. The last time I messed with it I finally got the headlights to do on off and bright, though still not in the proper positions, and I thought screw it I can live with brights being "on/off" and running lights being low beam and headlights being high beam.... But after a nice drive down the interstate at night about a week or so later all the truck drivers kept flashing me and having all sorts of fits... Eventually I thought the wheel must be about to fall off so I pulled off to check it out and realized I'd killed the tail lights. I've got brake lights blinkers hazards and headlights and reverse lights (I think) but getting nada on taillights... 

Edited April 13, 2022 by None_zero

[None_zero]

Sadly a few days ago I pulled up to a red light and a young man new to driving plowed into the back of me and ran me into the truck in front of me there I sat with Bettys poor little 720 ass sandwiched between a Nissan Titan and and a suburban. I was in the cab thinking well we've had a good run Betty, imagining all sorts of horrific conditions that I would find the salty old girl in when I eased out of the cab with my low back twinging from the impact.... Boy she took that hit like a champ barely a mark on her that wasn't already there or couldn't be brought back to right with a mallet and a sledge in short order... Just amazing. This truck is a devious tricky she devil that will have you tearing out your hair and at the end of your wits. But when the pasta hit the potatoes, she was a soldier.

[None_zero]

I suppose when it's all said and done I'll have to go on and pay the 75 bucks and buy that book you keep telling me I need @datzenmikebecause well it's true I need it and even though it annoys me to spend money on a manual seems like it would be worth it's weight in gold if only to eliminate the headache of the guess work

[None_zero]

On 3/17/2022 at 6:27 PM, datzenmike said:

Thought I could avoid the long story.

 

 

OK combustion does not happen instantly, it takes a small amount of time to burn and the hot gasses expand. The proper ignition timing starts the burn just prior to TDC so that there is time for the combustion process to reach maximum cylinder pressure at around 17 degrees after TDC. Any less and the crank, rod and piston are almost stacked in a straight line and the pressure isn't transferred into motion efficiently. Any more than 17 degrees and the piston is rapidly accelerating away and the pressure expands into an increasingly empty cylinder.

 

On a single plug engine the advance required is the longest and all manner of bad things happen. There is more time for heat energy to transfer into the top of the cylinder, combustion chamber and the piston top. The more heat transferred the less is available for expansion and pushing the piston down. More time for detonation or pre ignition to happen from the hotter combustion chamber. Also more time to form oxides of nitrogen, but we don't care about that. By having two ignition sources the burn time is drastically shortened so the timing is lowered from over 10 to about 5 degrees BTDC to properly hit that sweet spot of 17 degrees ATDC. Less pinging, less heat loss (more efficient) less nitrogen oxide produced.

 

I left out some information when I said that the distributor only switched to single plug by turning off the exhaust side. The module also automatically advances the timing because....... longer burn time with single plug. If you didn't, power would drop off.

 

Nissan's reason for single plug operation under heavy load conditions is " to reduce engine noise." I suspect that the 'noise' is simply the two flame fronts colliding and it sounds like a diesel or something.

 

So now you have the entire story.

And I'm a guy who loves the whole story. If I could get around to understanding the ins and outs of every subject available in the wide universe id do it. So If you ever find yourself tottering on the edge of explaining the bejeezuz out of something or not just know that I always would prefer more information to less and I appreciate you taking the time to share it 

[None_zero]

Oh I had one other question. .. the other day she randomly up and started running like crap again I think mostly she saw it was raining and dropping chunks of ice and couldn't resist the opportunity to make me stand in it. Anyways I pulled all the spark plugs and sprayed them off with carb cleaner and gave them a light brushing with a wire brush. They were nasty black and gunky, I adjusted the choke for a more lean condition to try and counter this, however while I was cleaning the plugs up I noticed that six plugs were filthy from the first three cylinders counting back from the front. But the last one on the intake and exhaust sides in the cylinder nearest to the fire wall the were oddly two toned. Like half of the spark plug was blackened and sooty and the other half was dry and kind of a tan color... What the hell does this indicate?

[datzenmike]

This is just a recent change so you may not have driven it enough to notice but, is the coolant level mysteriously low? Does it need topping up? Is there a mysterious steamy exhaust now than before? Keep an eye on your coolant level.

 

I would consider that the head gasket may be leaking and coolant is getting into the #4 cylinder. For 2 reasons... one is that the Z24 is prone to blowing the head gasket and two, the coolant becomes supper heated steam, and steam will blast areas of the combustion chamber clean as a whistle.

 

The preventative for the blowing of the HG is to re-torque the head bolts once a year to maintain proper clamping pressure on it. Have you ever re-torqued your head bolts?

[None_zero]

New update: ingot the tail lights working and the headlight switch is now Oriented properly with "on/off" as itself and brights as it's self and wonder of wonders even the running lights come on... Except now, no low beams. I finally gave up and decided for my old incandescent bulbs in this world of eye searing led headlights I can just use all four bulbs all the time. While I've been tinkering I noticed that the connections for the transmission sensors seem to be swapped the lines have been cut and spliced just after the connector so it's possible they were spliced wrong and are correct when they are mismatched what would the result be if the wires to the sensor toward the front of the tranny were swapped? I was doing some reading about it just from some Google searching and I came up with it would make it hard to shift or possibly to get stuck in gear I have noticed that it is hard to shift into first from a dead stop and it requires applying a bit of pressure for a second or two before it will go as well as needing to jam the clutch all the way to the floor when shifting to reverse to keep from grinding the gears which has the sound of to metal plates colliding edge on edge sort of. Does that sound like what it would be if those wires were swapped?

Edited April 13, 2022 by None_zero

[None_zero]

3 hours ago, datzenmike said:

This is just a recent change so you may not have driven it enough to notice but, is the coolant level mysteriously low? Does it need topping up? Is there a mysterious steamy exhaust now than before? Keep an eye on your coolant level.

 

I would consider that the head gasket may be leaking and coolant is getting into the #4 cylinder. For 2 reasons... one is that the Z24 is prone to blowing the head gasket and two, the coolant becomes supper heated steam, and steam will blast areas of the combustion chamber clean as a whistle.

 

The preventative for the blowing of the HG is to re-torque the head bolts once a year to maintain proper clamping pressure on it. Have you ever re-torqued your head bolts?

I have never retorqued the head bolts but remember I also don't have a z24 I've got the z20 not sure if that makes a difference but sometimes when I cut the engine off it diesels strangely and spits white smoke out the air intake. But wouldn't I see water in the oil if my head was blown.... I wanted to add that when I say diesels strangely I mean it makes a phtzzzzzzzzzzzzzz tik tik tik brrbrrbrr sound of that makes sense 

Edited April 13, 2022 by None_zero

[None_zero]

Also yes the coolant level is mysteriously low but I have a small leak from one of the bolts that bolts the casing of the water pump down so I figured it was probably from that and I haven't noticed any change to the exhaust except for the white smoke it normally spits out when you first start it turned black yesterday right when it ejected the ignition intake coil and started throwing it's tantrum

Edited April 13, 2022 by None_zero

[None_zero]

And when we are talking head bolts are you referring to the bolts that bolt the section of the engine under the valve cover the the section below and are

about even with the bottom set of exhaust manifold bolts? I've never really worked that deep in the block at all so I don't really know anything about it 

Edited April 13, 2022 by None_zero

[None_zero]

Also as a point of curiosity I have two wires the exit the harness near the battery one is R/Y and the other is R/L they are connected and I'm assuming it is because of some deleted part but inside the cab I also have two loose wires under the glove box of the same discription and they are both female connectors there is also a R/G wire same connecter loose I don't know what any of them are for but I've assumed it's something to do with I have no dome light and no door sensors and no radio no cigarette lighter or much of anything that isn't vital to the function of the truck. No a/c no power steering no cruise control.... You get the picture 

[None_zero]

On 3/17/2022 at 4:17 PM, None_zero said:

Ok so I'm grounding that wire somehow and it's telling the distributor to cut the exhaust plugs so I can't get torque to the wheels at low speeds?

 

As an aside I checked the timing and it was at 10° retarded but it was jumping down an extra 10° every so often (assuming that I'm remembering correctly that each line represents 10° difference with the middle line being zero) is that right ?

I can't believe no one snapped back in this with a "you're ten degrees retarded zero, it starts at no advance and goes up from there lol

[None_zero]

On 3/17/2022 at 6:27 PM, datzenmike said:

Thought I could avoid the long story.

 

 

OK combustion does not happen instantly, it takes a small amount of time to burn and the hot gasses expand. The proper ignition timing starts the burn just prior to TDC so that there is time for the combustion process to reach maximum cylinder pressure at around 17 degrees after TDC. Any less and the crank, rod and piston are almost stacked in a straight line and the pressure isn't transferred into motion efficiently. Any more than 17 degrees and the piston is rapidly accelerating away and the pressure expands into an increasingly empty cylinder.

 

On a single plug engine the advance required is the longest and all manner of bad things happen. There is more time for heat energy to transfer into the top of the cylinder, combustion chamber and the piston top. The more heat transferred the less is available for expansion and pushing the piston down. More time for detonation or pre ignition to happen from the hotter combustion chamber. Also more time to form oxides of nitrogen, but we don't care about that. By having two ignition sources the burn time is drastically shortened so the timing is lowered from over 10 to about 5 degrees BTDC to properly hit that sweet spot of 17 degrees ATDC. Less pinging, less heat loss (more efficient) less nitrogen oxide produced.

 

I left out some information when I said that the distributor only switched to single plug by turning off the exhaust side. The module also automatically advances the timing because....... longer burn time with single plug. If you didn't, power would drop off.

 

Nissan's reason for single plug operation under heavy load conditions is " to reduce engine noise." I suspect that the 'noise' is simply the two flame fronts colliding and it sounds like a diesel or something.

 

So now you have the entire story.

Oh wow I just reread all this and I realized a year or so ago you had told me that engines crave advancement and that I should set it to 10° advanced. I had done this but I remember thinking it sounded smoother and ran better lower than that and I dropped it back to about 5° and ran like that until the loss of ground caused the starter to quite and eventual all function to clease. It's good to know that my intuition works at least very occasionally lol I recall that we had a couple of confusing exchanges because I think you assumed it was a z24 as I guess most of them are but this has that z20 and the transmission no one knows about. I still never found anywhere to hook up my speedometer cable by the way and I've begun to assume maybe this one needs an electric gauge or something.

Edited April 13, 2022 by None_zero

[None_zero]

I am certain my knowledge of the history and function of this and other trucks like it has probably grown multiplicatively just from these exchanges with you and other site members, I greatly appreciate the assistance in with my education on this subject. I was in advanced auto parts the other day checking them for some parts and one of the guys chimed in with the comment "man I'm glad you know your ride" before sharing an anecdote about a gentlemen who was even more clueless than me when I started learning all this stuff and I have to admit that despite feeling the still very large lack of knowledge about these things I felt a fierce pride to be considered something more than an idiot with a set of keys to a machine I know nothing about.

[datzenmike]

3 hours ago, None_zero said:

New update: ingot the tail lights working and the headlight switch is now Oriented properly with "on/off" as itself and brights as it's self and wonder of wonders even the running lights come on... Except now, no low beams. I finally gave up and decided for my old incandescent bulbs in this world of eye searing led headlights I can just use all four bulbs all the time. While I've been tinkering I noticed that the connections for the transmission sensors seem to be swapped the lines have been cut and spliced just after the connector so it's possible they were spliced wrong and are correct when they are mismatched what would the result be if the wires to the sensor toward the front of the tranny were swapped? I was doing some reading about it just from some Google searching and I came up with it would make it hard to shift or possibly to get stuck in gear I have noticed that it is hard to shift into first from a dead stop and it requires applying a bit of pressure for a second or two before it will go as well as needing to jam the clutch all the way to the floor when shifting to reverse to keep from grinding the gears which has the sound of to metal plates colliding edge on edge sort of. Does that sound like what it would be if those wires were swapped?

 

Transmission switches are just switches, if the two wires are reversed it will still work. It would matter if wires from two different switches were swapped. The switch closest to the front just behind the clutch arm is fro the reverse lights.

 

No transmission switch will make the transmission hard to shift.

 

Grinding when shifting into reverse means the clutch is not fully disconnected. Check the clutch master cylinder fluid level. Important. This is hard on the synchros to leave it like this.

 

 

 

 

3 hours ago, None_zero said:

I have never retorqued the head bolts but remember I also don't have a z24 I've got the z20 not sure if that makes a difference but sometimes when I cut the engine off it diesels strangely and spits white smoke out the air intake. But wouldn't I see water in the oil if my head was blown.... I wanted to add that when I say diesels strangely I mean it makes a phtzzzzzzzzzzzzzz tik tik tik brrbrrbrr sound of that makes sense 

 

Still possible it's blown but much more likely on the Z24. Maybe put Z20 in your profile for the old guys like me that don't remember. Water does not immediately mix with the oil. It has to get past the rings first. Takes time. Don't worry about the head bolts if Z20. If the gasket is failing this won't help

 

A fast idle or if choke does not shut off when warmed up will cause this also. Warm up for 15 min and take a look at the choke plate... is it open or closed/partly closed???? It's important that the idle be around 750 or so.

 

 

 

 

1 hour ago, None_zero said:

I can't believe no one snapped back in this with a "you're ten degrees retarded zero, it starts at no advance and goes up from there lol

 

Unplug that extra wire and leave it.

 

Set the timing to 5 degrees on the Z20.

 

Each mark or point on the timing scale is 5 degrees.

 

 

 

 

 

 

 

 

 

 

 

 

[datzenmike]

1 hour ago, None_zero said:

Oh wow I just reread all this and I realized a year or so ago you had told me that engines crave advancement and that I should set it to 10° advanced. I had done this but I remember thinking it sounded smoother and ran better lower than that and I dropped it back to about 5° and ran like that until the loss of ground caused the starter to quite and eventual all function to clease. It's good to know that my intuition works at least very occasionally lol I recall that we had a couple of confusing exchanges because I think you assumed it was a z24 as I guess most of them are but this has that z20 and the transmission no one knows about. I still never found anywhere to hook up my speedometer cable by the way and I've begun to assume maybe this one needs an electric gauge or something.

 

Single plug operation would be around 10 degrees advance or if I thought this was an '80 720 with an L20B. Otherwise Z24 is 3 and Z20 is 5 degrees.

 

The speedometer drive pinion is on the right rear but if the original transmission was replaced with one from a 4x4 there is none. The speedometer on a 4x4 is driven from the transfer case.

 

 

 

 

[None_zero]

@datzenmikeok so I resolved the leaking coolant issue and the level stopped dropping so I don't think the head gasket is blown. It seems like maybe I had my vac lines scrambled somewhat and so I looked up a diagram and reconfigured I honestly can't wait to get paid again and order the fsm for this thing I'm dying to have my hands on that information. The vac diagram wasn't a perfect match but it was the closest one I could find with only 1 or 2 discrepancies. Two or three times now I've thought I had it set back right only to begin driving and have the performance drop off drastically. This last reconfiguration of the vac lines has returned the timing adjustment to a more normal range where I don't have to max it out to get the 5 degree advance I'm looking for. But the problem where I have to leave my foot on the clutch to keep the performance from dropping off heavily is back. I feel like there is more than one thing wrong here that is causing this problem and so everything I do only halfway fixes it and it either performs well while idling or while driving but never both. I had a run of about a week where it seemed like I'd resolved it finally but then it regressed I think because of carbon buildup on the plugs and it hasn't been right again since. Maybe I'm doing something wrong when I set the timing. I was watching videos about it trying to see if I missed something and the gentleman removed the vac line from the dizzy and capped it before setting the timing. I did not do this. So I guess I'll try to reset and take this step also. I've replaced several of the vac lines and because they were old and beginning to become crumbley but maybe I missed something there as well. How hot should the block get under normal conditions. I feel like maybe the coolant isn't circulating well although the temp gauge reads a nominal level. I really don't want to spend a bunch of money replacing parts but I may have to in the end the carburetor has more than once dropped a linking pin or lock screw that I've had to find and replace and I'm afraid there are other things I may have missed... The tranny has the mark ZL71B #4 it is a two wheel drive 4 speed. That's one of the tricky things about the truck is it's a Frankenstein. The cab claims it's a 4x4 with a z24. But the engine has the z20 478808 on its block and the tranny is marked as described above.

Edited April 14, 2022 by None_zero

[None_zero]

I think this is why I have so much trouble finding diagrams that match exactly because I don't know what all was removed and/or replaced and so often the diagrams list additional inclusions or exclude things that I have. It's a real head scratcher some times

[None_zero]

Or maybe I've just been at this so long I'm starting to see problems everywhere

[bottomwatcher]

https://www.nicoclub.com/datsun-service-manuals

You can try this although I am having issues on my phone.