I'm sorry if this is the wrong place to post this, I am new to forums. My name is Erik and would like to meet up with someone in my area with extensive knowledge of 720s. Willing to pay for an hour or so of your time to go over my 83 720 project.
Thanks for your time

Moved to 720 forum. You're more likely to get a response here.

What is your issue/problem?

Idling high, around 2500 to 3000. I believe it's something to do with the timing or fuel mixture . Here's what I've done to the truck, head gasket, timing kit,oil pump water pump, tune up parts, fuel pump. I am not an avid mechanic and this is my first time diving this deep into it but have read for countless hours before doing all work and have been meticulous as possible but I'm kind of stuck at this point. I can get it to idle down by placing firm pressure on the primary throttle bracket towards the drivers side. Adjusting fuel mixture doesn't seem to affect it,also the factory set idle screw has the cap pulled off so I have no idea how of that is. I don't own a timing light yet but I assume I need a good idle before that. In other carb pictures I see the dash pot is touching the adjusting screw,mine is not. Any help would be great!

waynosworld wrote:What is your issue/problem?

Idling high, around 2500 to 3000. I believe it's something to do with the timing or fuel mixture . Here's what I've done to the truck, head gasket, timing kit,oil pump water pump, tune up parts, fuel pump. I am not an avid mechanic and this is my first time diving this deep into it but have read for countless hours before doing all work and have been meticulous as possible but I'm kind of stuck at this point. I can get it to idle down by placing firm pressure on the primary throttle bracket towards the drivers side. Adjusting fuel mixture doesn't seem to affect it,also the factory set idle screw has the cap pulled off so I have no idea how of that is. I don't own a timing light yet but I assume I need a good idle before that. In other carb pictures I see the dash pot is touching the adjusting screw,mine is not. Any help would be great!

waynosworld wrote:What is your issue/problem?

So I'm assuming at this point it is fuel related, I can turn the idle screws in or out as much as I want and it does not affect the high idle, the only thing that does is pressure on the throttle bracket also pressing down on the accelerator pump arm which does the same thing. So too much fuel? Has no problem starting and choke works properly.

83720z24 wrote:

waynosworld wrote:What is your issue/problem?

Idling high, around 2500 to 3000. I believe it's something to do with the timing or fuel mixture . Here's what I've done to the truck, head gasket, timing kit,oil pump water pump, tune up parts, fuel pump. I am not an avid mechanic and this is my first time diving this deep into it but have read for countless hours before doing all work and have been meticulous as possible but I'm kind of stuck at this point. I can get it to idle down by placing firm pressure on the primary throttle bracket towards the drivers side. Adjusting fuel mixture doesn't seem to affect it,also the factory set idle screw has the cap pulled off so I have no idea how of that is. I don't own a timing light yet but I assume I need a good idle before that. In other carb pictures I see the dash pot is touching the adjusting screw,mine is not. Any help would be great!

OK, I don't know a lot about 720 down draft carbs or any down draft carb for that matter, but I have help diagnose problems with them and got them back on the road.
Did it run correctly before the head gasket change, and had you adjusted it before trying to start it the first time after the head gasket change, or did you adjust it thinking that the carb was the issue before realizing it was a head gasket problem?
What I am basically asking is if it ran good before the head gasket change, and then it didn't run good afterwards without touching the carb?
Did you pull the carb off the intake manifold when you changed the head gasket?
Are you sure you got all the wires put back on the carb after the head gasket change?
What area of Portland do you live?

The truck was given to me by a friend, had a blown head gasket and bad fuel pump. His symptoms prior to my possession were stalling as soon as moving, I assumed that was fuel pump. Was running good before those symptoms for him. However he did rebuild the carb thinking that was his issue. I can't verify the quality of rebuild,I didn't mess with the carb till I had it back together and running. I did pull the carb of intake to clean out the intake thoroughly but did not adjust anything. I live in sw portland, Multnomah village area.

He rebuilt it, well that would be over my head now, the carb was pulled apart.
I hate downdraft carbs, I can never get them to run correctly after I rebuild them, I have to have them sent out, and these are carbs without electronic s*** on them, so yours is way over my head.
If it had been untouched, I may have been able to help, it can only be so many things if untouched.
I hope someone else chimes in to help you, if you were not in Portland I would say buy a Weber, but you are in the Portland emissions zone.
Maybe you could find a used carb like yours in a wrecking yard that hasn't been touched, there is a 1984 Nissan 720 in the Sherwood pick and pull, don't know if the carb is still there though.

Thank you for quick response and honesty, I know some people would come over and take my money with out knowing what they're doing! I'll look into my other options, thanks

The high idle sounds like a vacuum leak to me. Have you tried spraying carb cleaner everywhere and see if it changes the idle at all?

float_6969 wrote:The high idle sounds like a vacuum leak to me. Have you tried spraying carb cleaner everywhere and see if it changes the idle at all?

I did spray some around yesterday but ran out shortly, will pick some more up today. Most of the vacuum lines and caps are newer because most of the emissions have been removed. The only emission part that hasn't been deleted is one vacumm line from bottom of egr to the bottom of the part directly next to it toward the drivers side, short line about 4 inches. Still a little confused if the egr is still in use or not.

If the EGR valve is still plumbed into the intake manifold, the valve could be stuck open and can cause high idle issues. It won't show up when you spray carb cleaner because it's drawing air in from the exhaust manifold(s). If you don't have emission compliance to deal with, then I would remove the EGR tube and cap it on both ends.

float_6969 wrote:If the EGR valve is still plumbed into the intake manifold, the valve could be stuck open and can cause high idle issues. It won't show up when you spray carb cleaner because it's drawing air in from the exhaust manifold(s). If you don't have emission compliance to deal with, then I would remove the EGR tube and cap it on both ends.

Let's say the egr valve is the only emissions part I keep, what should be plumbed to where as far as vacuum lines, I am going to remove,take apart and clean egr tonight. Also what would one use to plug egr tube ends on exhaust /intake manifolds?

I'm assuming I could get properly threaded caps from a good hardware store?

That I don't know.

float_6969 wrote:That I don't know.

http://imgur.com/a/9BNKr
So I haven't got into the egr yet but have found that I don't have power to the anti dieseling solenoid, could this be a source for my high idle problems? The other threads I read about it mentioned that it would affect idle but didn't say in what way. I traced the wire (blue /white)back to what I believe is a capacitor?located on the harness for the wiper motor. In the picture of the plug (male ends) the blue and white wire goes to the plug next to empty spot then to capacitor, and the other connection on capacitor goes to what looks like the blank spot in plug, also the tiny wire for ground. Let me know what you think, thanks!

http://hubpages.com/autos/The-Datsun-an ... t-Tell-You
Now after reading this article I'm thinking this relay could be my problem. The person that installed new fuel pump I believe hard wired it in, as soon as the key is turned to the on position you can here the pump constantly running. Also forgot to mention that the truck has run on a few times after shut off.

Ignore the capacitor comment, wrong wire. I'm unwrapping some of the wiring harness to see exactly where the b/w wire leads to for anti dieseling solenoid

The anti-dieseling solenoid is the idle fuel cutoff valve, it will not idle properly without power to it, to get it to run at all one would have to keep the rpms up high to where the idle circuit wasn't being used.
In theory every time one let off the pedal it would die unless one were to keep feathering the pedal giving it fuel to run on, you need to wire the solenoid for power, maybe all your issues will go away.
In my first post to this thread I asked you, "Are you sure you got all the wires put back on the carb after the head gasket change?", you need to connect all the wires to the carb, otherwise it will never run properly.

waynosworld wrote:The anti-dieseling solenoid is the idle fuel cutoff valve, it will not idle properly without power to it, to get it to run at all one would have to keep the rpms up high to where the idle circuit wasn't being used.
In theory every time one let off the pedal it would die unless one were to keep feathering the pedal giving it fuel to run on, you need to wire the solenoid for power, maybe all your issues will go away.
In my first post to this thread I asked you, "Are you sure you got all the wires put back on the carb after the head gasket change?", you need to connect all the wires to the carb, otherwise it will never run properly.

All wires were connected that go directly to the carb. The solenoid wasn't powered because the power goes into the harness and then goes to a vacuum switch on the passenger side which had been removed with other emissions parts from prior owner. The previous owner left all vacuum lines and parts with truck thankfully, the solenoid now has power. I am currently restoring all vacuum lines and emissions parts to start fresh. The symptoms you described though lead me to think it's still a vacuum leak and not the shut off solenoid, it has no problem starting. But once started it races up to 2500 to 3000 rpm.

83720z24 wrote:

waynosworld wrote:The anti-dieseling solenoid is the idle fuel cutoff valve, it will not idle properly without power to it, to get it to run at all one would have to keep the rpms up high to where the idle circuit wasn't being used.
In theory every time one let off the pedal it would die unless one were to keep feathering the pedal giving it fuel to run on, you need to wire the solenoid for power, maybe all your issues will go away.
In my first post to this thread I asked you, "Are you sure you got all the wires put back on the carb after the head gasket change?", you need to connect all the wires to the carb, otherwise it will never run properly.

All wires were connected that go directly to the carb. The solenoid wasn't powered because the power goes into the harness and then goes to a vacuum switch on the passenger side which had been removed with other emissions parts from prior owner. The previous owner left all vacuum lines and parts with truck thankfully, the solenoid now has power. I am currently restoring all vacuum lines and emissions parts to start fresh. The symptoms you described though lead me to think it's still a vacuum leak and not the shut off solenoid, it has no problem starting. But once started it races up to 2500 to 3000 rpm.

It will not have trouble starting if you pump the gas pedal a few times because the accelerator pump will give it some gas to run on, and then it will run on the primaries if the idle screw is set high enough.
I suppose it could also have a vacuum leak or could have been put together wrong when torn apart also, but the inti-run on valve cuts the fuel off for the idle circuit, that way it doesn't diesel or back fire when shut off, because there is no fuel anymore, that is why Weber carbed engines diesel, they have any such valve.

83720z24 wrote:

waynosworld wrote:The anti-dieseling solenoid is the idle fuel cutoff valve, it will not idle properly without power to it, to get it to run at all one would have to keep the rpms up high to where the idle circuit wasn't being used.
In theory every time one let off the pedal it would die unless one were to keep feathering the pedal giving it fuel to run on, you need to wire the solenoid for power, maybe all your issues will go away.
In my first post to this thread I asked you, "Are you sure you got all the wires put back on the carb after the head gasket change?", you need to connect all the wires to the carb, otherwise it will never run properly.

All wires were connected that go directly to the carb. The solenoid wasn't powered because the power goes into the harness and then goes to a vacuum switch on the passenger side which had been removed with other emissions parts from prior owner. The previous owner left all vacuum lines and parts with truck thankfully, the solenoid now has power. I am currently restoring all vacuum lines and emissions parts to start fresh. The symptoms you described though lead me to think it's still a vacuum leak and not the shut off solenoid, it has no problem starting. But once started it races up to 2500 to 3000 rpm.

So I believe I screwed up royally, I thought I was being thurogh when I marked the timing chain (colored link) on cam shafts sprocket before I did timing kit. So I reinstalled the new timing kit accordingly, but I'm assuming it had jumped timing after the chain guide on drivers side broke (found the part in oil pan) in the book it clearly has the colored link directly over the number 2 mark. Please confirm my beginners mistake, thank you. http://imgur.com/QLi8m0H

I'm assuming having two teeth off on timing is the route of my issues?

83720z24 wrote:I'm assuming having two teeth off on timing is the route of my issues?

OK I know this is not going to make sense, and I cannot tell you how you set it up the first time because you don't have a photo of it, but on an L20b the bright links are there for only setup purposes, once you turn the engine over, the bright links only align every 12 turns of the crank or something like that, I cannot remember anymore it's been so long since I thought about that, I just know in the L20b they come up in a different spot every time they come around, why would a Z24 be any different.
Here is your photo.

I don't know what the Z24 cam is supposed to look like when at TDC on the crank, so I cannot tell you if yours is right with a photo of it, but maybe someone on here does know what it's supposed to look like, here is what the L20b cam is supposed to look like when at TDC, but yours is a Z24, the Z24 should have it's own look that others would recognize if you posted a photo of it.

http://imgur.com/a/9T21Y
I've checked that it's at tdc by checking the mark on the crank shaft pully and by looking in the cylinder. The cam shafts lobes are pointing down wards on number one. So the question is, should the colored link be over the two mark at tdc on a z24? Hopefully someone can answer this for me! Thanks for your input

Well I turned the crank shaft around a handful of times and it seams that the platted chain ends up at different locations while being cycled. So I'm assuming the only way to double check is to remove timing cover and verify how many links are between the timing marks.

That's what he's trying to say. Don't pay any attention to the location of the colored link. It rarely lines up. It's ONLY there for when you FIRST put the timing chain on when it's new. There should be a mark on the crank for TDC, and a mark on the cam/cam gear for TDC. I don't know Z engine's AT ALL, so I can't tell you any more than that. I can also tell you that if it was really off by 2 teeth, it probably wouldn't run.

float_6969 wrote:That's what he's trying to say. Don't pay any attention to the location of the colored link. It rarely lines up. It's ONLY there for when you FIRST put the timing chain on when it's new. There should be a mark on the crank for TDC, and a mark on the cam/cam gear for TDC. I don't know Z engine's AT ALL, so I can't tell you any more than that. I can also tell you that if it was really off by 2 teeth, it probably wouldn't run.

OK, so I just got done redoing valve lash using the cold settings found on this site 0.008 intake and 0.009 . I can't remember what I set them at prior but it was way off. My garage no longer reeks of unburned fuel and the engine runs so much better. I still have the high idle at about 2000, if I apply pressure on the throttle bracket it idles down nicely. But the adjustment screws seem to do very little, I have the idle screw turned way out to get to the current idle speed, and I can turn the factory set mixture screw in or out as much as I want without any affect. I will take apart and clean egr still to ensure its not stuck. I did install a new fuel pump, any chance it could be pumping too much fuel? The pump came up as compatible.

I will also pull the viewing glass off of carb tomorrow to ensure that the float is properly adjusted