Vacuum Line Placement - 1986 Z24 gas motor

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
lego126
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby lego126 » Mon Mar 26, 2012 10:14 am

I found it!!! I finally read through your entire post over and looked at all the pics over and over again...and over and over.. Finally. The vac line I was talking about is the one that comes from underneath the breath and runs across the valve cover and goes on the right side of the breather, on that little motor thing. But Mine had a T connector and also ran back across the valve cover to the left side of the carb, BUT it was suppose to go from left side of carb, under the breather, runs along with the brake lines to the far right corner of the engine compartment, then forward to just in front of the canister above the ignition coils. Basically the longest vac line in the engine compartment. Yes we were talking about the same line. But some jackleg put a t connector on in cause he couldn't see the vac line nipple on the bottom side of that.. thing it connects too.


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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Mon Mar 26, 2012 12:22 pm

Good job!

stepcaw
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby stepcaw » Sat Sep 01, 2012 4:42 am

Hi, I'm new here. I've got a 1990 D21 chassis that originally had a NA16 engine (NZ market). It's been replaced with a carburetted (DCH340 I think) Z18, engine (probably circa 1980). It's got quite a few caps on the inlet manifold and one on the carburettor.
So I was browsing for some info on the web when I came upon FBM's Z24 guide. On my vehicle there is no hard lines A & B only C going to vacuum diaphragm on the distributor. The metal mushroom that line D is connected to isn't there and the temperature valve where the top radiator hose enters has only two hose tails with no hose connected at present. There's no vacuum switches. I don't think I've got the correct air filter hosing either.

I've tried getting info from Haynes or other manuals but there not comprehensive enough. Nearly always showing L series engines. Would I be best buying the 720 factory service manual (up to 1983) to get it sorted? I guess the diagram at the end of the thread was from the factory service manual? The engine runs OK when hot but has big flat spots when cold which I can't live with. Any advice appreciated!!

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sat Sep 01, 2012 5:25 pm

Sorry, but I don't have any info on what your setup should look like. I think it will be a nightmare to get it all straight like a factory setup. Is there any way you can just delete lines and cap off the vacuum ports?

XavierBK
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby XavierBK » Fri Oct 19, 2012 9:52 am

I finally got around to eliminating all the extra vacuum lines while rebuilding my carb. Problem is.. the truck is running super rich now and will barlely idle, and die if left idling too long. It does feel to have more power but it also seems to continue accelerating for a short time after lifting off the accelerator.

One question I had about eliminating the lines... where should the vacuum advance be hooked up? Does it matter? I'm pretty sure I traced the existing hoses correctly and kept it hooked to the same spot, a double nipple on the intake.

Also, the vacuum switches that were on the passenger side, should they be left plugged in or is it OK to disconnect them after deleting the vacuum lines?

Any other tips for trying to solve this running rich scenario? I'm not that familiar with carbs and how to tune them other than rejetting and I've only done that on motorcycles.

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Fri Oct 19, 2012 1:31 pm

I've never done the vacuum delete myself. You need to make sure that all the ports on the intake manifold and carb are properly capped or the vacuum leak will cause poor performance.

I think the vac switches can be disconnected from everything, wiring and all.

XavierBK
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby XavierBK » Fri Oct 19, 2012 5:56 pm

Yup, they are all capped. Picked up a vacuum cap kit with this task in mind.

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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby hbpignosePA » Fri Jan 18, 2013 9:23 am

unless I am just an idiot (and its debatable) i have a few extra lines and ports that are not mentioned in your guide.... I will double check tomorrow but I have a third vacuum switch on the passenger side that i don't see anywhere in your guide. There are two ports off of that and I am also missing one on the pass side of the carb. if i get pictures i would love some imput from the truck gurus....

officalfordtow
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby officalfordtow » Tue Jan 29, 2013 2:45 pm

i noticed that there was no mention about the 3 or 4 restrictors that are inside the vacuum lines, that are for predetermined measured vacuum

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Tue Jan 29, 2013 3:32 pm

officalfordtow wrote:i noticed that there was no mention about the 3 or 4 restrictors that are inside the vacuum lines, that are for predetermined measured vacuum
Since this post is just showing where everything hooks up, that part was not mentioned. Feel free to add your knowledge and show us where to find them on the stock vac lines.

jamjim931
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby jamjim931 » Thu Apr 04, 2013 8:09 am

This diagram has been great but im running into a problem. under section 3 where you state "There is one more vacuum line near the vacuum canister." my truck does not have that piece or that hose that is supposed to travel to the passenger side of the truck. in the picture two before section 4 it states that those hoses are supossed to connect at a T, that T doesnt exist for me. i have an 85 z24 king cab and the vacuum system was a mess when i got it some hoses had screws in them others not there or just hooked up wrong so im not sure if its missing or im not supposed to have it. any help would be great. thanks

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Thu Apr 04, 2013 2:27 pm

I can't tell you for sure what yours is supposed to look like. If you duplicate the hose layout in the post, you should have things close enough to run well. Although I made the post and showed how my truck was set up, I cannot guarantee that it's exactly like the factory. It had 193K miles on it when I got it, yet it seemed that everything was original.

MR2Di4
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby MR2Di4 » Mon Sep 09, 2013 1:37 am

Just registered to say THANK YOU! to FastBoatMan for the excellent guide with pictures and everything! Just got a 720 from my brother and it's vacuum hoses were all screwed up, now I can roll back over to his place and watch his jaw drop when he sees how his truck is supposed to run. Major kudos to you!

MR2Di4 :cool:

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Mon Sep 09, 2013 5:54 am

MR2Di4 wrote:Just registered to say THANK YOU! to FastBoatMan for the excellent guide with pictures and everything! Just got a 720 from my brother and it's vacuum hoses were all screwed up, now I can roll back over to his place and watch his jaw drop when he sees how his truck is supposed to run. Major kudos to you!

MR2Di4 :cool:
When it helps people and they say "thank you", it makes my day! You are very welcome.

Aichski
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Aichski » Mon Oct 21, 2013 7:09 am

Any idea where i can get the vacuum line diagram for the z22 motor or do you think the z24 is much the same? Thanks heaps for the detailed write up. :biggrin: .. Amazing stuff buddy. Thanks to you I also did my own ball joints ;) Once again and huge thanks :chuckle:

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Tue Oct 22, 2013 8:14 am

Sorry, but I don't have any info about the Z22 engines.
I am always glad to hear when people use the DIY threads on here to help with repairs. I hope to do a rear brake cylinder DIY soon. Good luck.

Glenn Schoettlin
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Glenn Schoettlin » Sun Dec 01, 2013 1:34 pm

I think your truck is almost exactly like mine. I got my truck from the Nissan dealership in Sept 1985. The window sticker calls my truck a 1986 Long bed 720 Pickup truck. Mine is the ST model which has some extra stuff like nice wheels and a pop top and sliding rear glass window. But it's the same engine and vacuum lines as yours. So your pictures on the vacuum lines really is a big help to me. Thank you for taking the time to do an excellent job of showing where all the vacuum lines go and come from. I love the way you show which way the picture is orientated by showing which is the driver side of the picture and which is the passenger side as well as the front, back and top and bottom in the picture as well as showing the vacuum lines with dotted ink marks or arrows. That's a great way to show how to work on these trucks and where the vacuue lines go.

I never did know where those hard lines went to unit I read you thread today. Now I know where the vacuum advance hose comes form and where it goes.

Great Job fastboatman. :dblthumb:


fastboatman29212 wrote:Stay tuned. There are a few more vac lines (believe it or not) that I have not shown yet. Photos coming soon! Anyway, I recently found some vac lines that I didn't know were there. All of this stuff was designed for a reason and by people who are way smarter than me.

I decided to make this post because Aven was asking for help AND we frequently get questions about vac lines and rough running engines. Usually people will just delete the vac lines and cap off the ports. That's fine if you do it properly AND CAP THEM ALL OFF, (except the one to the vacuum advance of course)!

So far, I have found at least 6 ports on the intake manifold. Interestingly, there are 3 lines that connect to vacuum switches which then have electrical connections to the computer in my '86 (an '86 has a electronically controlled carb). I've been wondering how performance would be affected with those vac lines deleted. Hmmmmm! More reading to do I guess. LOL!

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sun Dec 01, 2013 3:11 pm

If it helps people, then it was worth my time. Thanks for taking time to give the :dblthumb:

macklen
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby macklen » Mon Dec 30, 2013 3:19 pm

Fastboatman... you The Man. I bet I'm not alone in owing your posts a great deal. Keep it up, thanks for sharing.

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Mon Dec 30, 2013 4:50 pm

Thanks. I'm glad it helps. Have fun with the truck. I like mine.

stufflda
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby stufflda » Fri Jun 13, 2014 8:51 am

I just re-inherited a 1986 720 pickup. When I owned it before, the vacuum hoses were never right and it would only pass emissions on a happy day. I think I have everything right except two hoses.

First. the bigger hose coming off of the bottom of the air cleaner is gone, and I don't know where it connects. When I saw your picts about a month ago, I think it is hose C? maybe...

Second, there are two hoses coming off of a little round Vacuum Control Valve. The bottom hose is a mystery on where it goes. It has never been hooked up to anything. I cap it off with a screw and the truck runs better, but I think it might be the cause of dumping to much Hydrocarbons out the tailpipe. Does your Part two cover that, if you have made it yet?

Thanks so much for your service to the community by the way!

stufflda
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby stufflda » Fri Jun 13, 2014 9:37 am

Fastboatman, thanks for the quick reply... I have been to that URL before, but I don't see a link to the Vacuum Line placement project. By the way nice visuals on the Carb rebuild, I want to rebuild the carb on this truck, and wasn't going to attempt it, but now I can.

Ruhaa
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Z24 motor

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Ruhaa » Tue Jun 24, 2014 5:56 pm

I removed all vacuum except the vac advance a brake power booster no canister either runs great but at a high idel. Does the canister help? It seem to me there a lot of vacuum at the in take. Any ideas?

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Tue Jun 24, 2014 8:06 pm

If all the vacuum lines are disconnected, then you will need to place caps on the open vacuum ports that are on the intake manifold. A vacuum leak somewhere will cause the idle to be high. The canisters are not needed.

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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby AZhitman » Sat Mar 07, 2015 12:51 am

Update for everyone - Thanks to fastboatman, the pictures and article are now forever archived and hosted in a fantastic article series!

You can follow the link in the first post of this thread, or here it is again: Nissan 720 Pickup Truck Vacuum Hose Routing and Repair Guide

Bookmark it, share it, post the link on other sites, share it with other 720 owners...

...and most of all, please give fastboatman a HUGE hand for putting together such a useful and helpful DIY reference article!!! :dblthumb:

busterone
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby busterone » Mon Apr 06, 2015 6:49 pm

Great work! I have removed all the vacuum and emissions, but if I ever need to restore it to factory, this will get it done. Thanks.

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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Fri Apr 15, 2016 8:01 pm

Hi, I recently purchased a1985 Nissan 720 4x4 with roughly 91,000 miles. The owner befor me butchered the vacuum lines. So I was just going to replace all of the lines using your very informative post. All I was wondering is what size vacuum lines I need and roughly how much of each line. Also the owner before me just had the carb rebuilt, but he still felt the need to screw with the idle adjustment screw ( because he couldn't get it to idle correctly, but from the condition of the vacuum lines I can see why) so I was wondering where that should be adjusted to. Thank you very much!

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Fri Apr 15, 2016 8:20 pm

I recommend sizing the vacuum line inner diameter by checking the T and Y connections. Take some of those connectors to the store and select the size that feels snug. There may be as many as 3 different sizes. I don't think having the wrong size will matter much unless it fits very loosely and actually leaks.
Capping some of the lines may be useful as you sort through it and find the right fittings.

If I were you, I'd actually consider capping all the vacuum ports on the carb and see how it runs that way.
If it runs good then keep it that way. Good luck.

Nissan720newb
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Fri Apr 15, 2016 8:25 pm

Okay, thank you, so I can cap all of the carb ports? Just leave the lines that go to and from the intake?

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fastboatman29212
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Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Fri Apr 15, 2016 8:30 pm

You will need to keep the vacuum line that goes to the distributor so the vacuum advance will work.


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