Vacuum Line Placement - 1986 Z24 gas motor

1980-1986 Datsun 720 forums. All 720-specific topics and discussion can be found here.
Nissan720newb
Posts: 7
Joined: Fri Apr 15, 2016 7:51 pm
Car: 1985 Nissan 720 4x4

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Fri Apr 15, 2016 8:33 pm

Okay, I will try that, but what about the idling screw?


User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Fri Apr 15, 2016 9:12 pm

The factory sets the idle mixture screw and then seals the hole with a plug. If the plug is gone, then slowly turn the screw in until it stops. Make sure you count how many turns it takes until it seats gently. Then back the screw out until it's back where it was. Warm the engine to operating temperature. Then turn the screw in until the engine stumbles and then back it out about 1/2 turn. It should idle smoothly (unless you have a vacuum leak).
The factory service manual says to adjust the screw until you get the proper carbon monoxide reading. Good luck with that. I don't have that kind of equipment. Good luck.

Nissan720newb
Posts: 7
Joined: Fri Apr 15, 2016 7:51 pm
Car: 1985 Nissan 720 4x4

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Sat Apr 16, 2016 6:58 pm

Alright, so I did what I could with the vacuum lines, got it to run a little better, but I have another issue, I tried doing what you suggested with the idle screw but when I tightened the idle screw to try to drop the idle there was no change I seated it all the way and it ran the same, any suggestions?

User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sat Apr 16, 2016 7:05 pm

The idle mixture should be the only fuel circuit supplying fuel at idle. So that makes me think the throttle plate is open too far. Maybe you can use a tach to check RPMs and bring the idle down to 650 or lower by adjusting the throttle screw. Then the idle mixture screw might have some effect. How many turns did your screw require to get it to seat?

Nissan720newb
Posts: 7
Joined: Fri Apr 15, 2016 7:51 pm
Car: 1985 Nissan 720 4x4

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Sat Apr 16, 2016 7:23 pm

Which screw is that? It was roughly 1 3/4 turns

User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sat Apr 16, 2016 7:43 pm

See pictures 1 and 3 at this link. Throttle adjusting screw.
720-carburetor-reference-pics-t521844.html

Nissan720newb
Posts: 7
Joined: Fri Apr 15, 2016 7:51 pm
Car: 1985 Nissan 720 4x4

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby Nissan720newb » Sat Apr 16, 2016 7:57 pm

Okay, I don't have a tach right now, but will it be okay if it just idles a little high for a while?

User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sun Apr 17, 2016 7:06 am

It will be OK. Just turn the Throttle adjusting screw out to lower the idle RPMs until it seems about as low as it can go. Then play with the idle mixture screw.

BranS
Posts: 10
Joined: Wed Apr 20, 2016 8:42 pm
Car: 1985 nissan 720 4x4 z24

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby BranS » Sat Apr 23, 2016 10:53 am

Hey, great help on this. One thing that would be helpful is knowing names of things lines are going to,egr ,thermal vacuum switch ect
So I found that my carb vent line was missing and broken off at carb.... any one know what that'll do to me? It started pinging on me, but not sure if that's related. About to replace egr valve hoping that helps,
Seems to be sticking. Cali 85 4x4 thanks
:inout:

User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sat Apr 23, 2016 7:12 pm

If the carb vent line is off it should still run fine. It just equalizes pressure so the fuel bowl stays at atmospheric pressure. Pinging likely means you need to check the distributor timing and vacuum advance. Make sure it's working.

BranS
Posts: 10
Joined: Wed Apr 20, 2016 8:42 pm
Car: 1985 nissan 720 4x4 z24

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby BranS » Sun Apr 24, 2016 4:36 pm

Can't figure out vacuum advance . Doesn't seem to change. Egr didn't help but old one was definitely not functioning right. Trying draining more fuel and recheck ing vacuum leaks. Got two compression testers that aren't working... no way I'm running with no compression. ..... ahgg.

User avatar
fastboatman29212
Posts: 497
Joined: Sun Jul 25, 2010 6:45 pm
Car: left this forum. Sold my truck.
Location: South Carolina

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby fastboatman29212 » Sun Apr 24, 2016 4:53 pm

To check the distributor, you will need a timing light. Disconnect the vacuum hose on the distributor and start the engine. Use the timing light to see what the advance is set at. Next rev the engine and use the timing light to see if the timing changes as the engine RPMs go up. That checks the mechanical advance of the distributor.
Shut the engine off. Next, take a spare piece of vacuum tubing and connect it to the vacuum port on the distributor. Put the other end in your mouth and suck gently. You should feel the distributor hold suction, kinda like sucking air out of a coke bottle. It should pull back a little. If not, then maybe the vacuum advance on the distributor isn't working. Truck would still run but performance would be very poor at speeds.

Next, reconnect the real vacuum line to the distributor. Start the engine and use the timing light to see if the timing mark moves as the RPMs go up. The timing mark should move even further now that the vacuum advance is connected.

Worth a try. Easy to do and free if you can borrow a timing light from the auto parts store or a friend.

BranS
Posts: 10
Joined: Wed Apr 20, 2016 8:42 pm
Car: 1985 nissan 720 4x4 z24

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby BranS » Sun Apr 24, 2016 10:35 pm

Thanks I'll try that. I did check timing and see it move when reved up, but didn't check without dis vac connected. Should it advance or retard?Somthing gotta give here....that pinging might not be pinging after all. Sure seems like it, only under load and about 2200 rpm. Running out a ideas... probably wasted 10 hrs so far. Not the way I wanted to be working on her....
Thanks very much for your replys.

415714
Posts: 3
Joined: Mon Oct 24, 2016 9:53 pm
Car: 1986 Nissan 720 pickup

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby 415714 » Mon Oct 24, 2016 10:03 pm

I could really use someone's help:/ I don't have a carburetor vent tube to go on the canister. Or where can I find mine? Maybe mines just different idk. Please someone help me out. I saw the pictures but mine doesn't have the tube coming out of the front of the carburetor.

DEZERTRAT
Posts: 3
Joined: Mon Mar 27, 2017 11:33 am
Car: 1984 720 King Cab 4x4
Location: West coast

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby DEZERTRAT » Wed Apr 05, 2017 6:48 pm

Just posted for the first time w/new topic but maybe this goes here? Active Vacuum Line project going, and running into several missing parts already from PO gutting... Thank you for any leads on where to find this!

I'm looking for a vacuum switch or "switch assembly-vaccum" part no 22360-D0202, (22360M in diagram) its a vacuum switch with 2 electrical prongs. It is found on the passenger side, mounted left of carb.
Nissan dealer doesn't have it and its discontinued on the one site I found with a listing for it.
Image


It appears identical to the one next to it on diagram, part no 22360-W7000 which as 4 prong elec connection (which I am going to order today.)

I need to restore my vac emissions system in order to pass CA Smog. I've hit a wall with this part! PO deleted many lines and also took out the vacuum switches that I need and who knows what else. :gotme :confused: Thanks for any leads.
Pics:
Image
Image
Image
Image

720Girl23
Posts: 2
Joined: Tue May 16, 2017 9:13 pm
Car: 1980 Datsun 720 (King Cab)

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby 720Girl23 » Tue May 16, 2017 9:24 pm

I have a question but I can't ask without using pictures, can someone tell me how to post pictures in my replies?!

720Girl23
Posts: 2
Joined: Tue May 16, 2017 9:13 pm
Car: 1980 Datsun 720 (King Cab)

Re: Vacuum Line Placement - 1986 Z24 gas motor

Postby 720Girl23 » Tue May 16, 2017 9:25 pm

I have a qu question regarding this step by step post on where to the hoses go and what to do if I only have one circular container on top of the black canister but it's kind of hard to explain without using pictures. Can somebody tell me how to post pictures on this feed?


Return to “Datsun 720”

cron