Z24 Hitachi Carb Rebuild DIY 1984-86

[fastboatman29212]

For reasons of my own, I decided to rebuild my Hitachi carb. Many owners choose to buy a Weber carb instead and I have never heard anyone have regrets about doing so.

I imagine if you are reading this, you are considering a rebuild. Also, studying this thread may help you understand and solve a carb problem that you are having.

I will add more as I build this thread. Feedback is welcomed.

You can now find all of my 720 repairs posted on a separate website. Link = http://www.720NissanTrucks.weebly.com.

Here is the link to the photobucket album if you choose to view it there.

http://s618.photobucket.com/albums/tt26 ... 20Rebuild/










The anti-dieseling solenoid is very hard to loosen once the carb is off the truck because you don't have good leverage. That is why getting it loose before actually removing the carb is probably a good idea. I found this out the hard way. To get to the solenoid, you must swing the accelerator pump lever arm up and out of the way. So let's do that first.

































































OK, Here's the Middle Section Rebuild









































































































































That's all there is to it! Easy, right?

[breadbox]

That's awesome.

[fastboatman29212]

That was a lot of work, but it was fun!

[woodbutcher5691]

So I was right on the quiz Great post

[mbunzel51390]

I am new to the 720 and have been trying to fiddle around with the carb a little bit cause I think it might be one of the causes for it not running right. I have a few questions about the carb in general. In the first picture the throttle like plate on the top left side of the chamber what exactly is that for. Second does the injector on the right side of the carb ever do anything.

[fastboatman29212]

If you are referring to the choke plate, then it is imporrant for starting when cold.

[SCBlake1988]

Thank you for the great walk through.

I just did it but ran into trouble once started. There is a gas leaking pretty bad around the fuel inlet where that little fuel filter is. Does that mean the the float pin is damaged? There was no fuel in the float when I took it apart so I think that is OK.

Blake

[SCBlake1988]

Nevermind - fixed gas leak with some rubber gaskets.

[ofarrellfitz]

Hey great work with the documentation!

So that was a stock carb rebuild kit? Got a part number?

I'm looking at the walker products Part # 151000B from O'Reilly, or some other place.

Is this the correct match? Is there a better one?

Thanks!

[fastboatman29212]

Yep! That's the right kit. I showed the kit in the 2nd pic of the DIY thread.

Here it is again.

[Glenn Schoettlin]

Thanks Fastboatman29212:

I'm going to probably need one of those kits as my carburetor is not working good anymore. The fuel level is way too high in the sight window and the truck is hesitation when I step on the accelerator from a stop at idle speed. It's idling OK and starting OK but when I give it gas I have to nurse the throttle to keep it from dying as it hesitates badly when I try to give it gas. It's only does this intermittently right now.

I put in a new Engine Control Module as the old was was not working right in the cold weather. No spark on the old one. The new one is working much better and I get spark on both sets of spark plugs.

I took the exhaust plugs out and replaced them with some new NKG spark plugs that I got from AutoZone a while back. The old plugs were very dirty and not that old. Not quite a year old. Maybe a year and a half. But were getting way too much fuel and had black carbon on them.

I recently added Seafoam to the gas tank two times in two different full tanks 126 gal of gas. Another Nissan mechanic said that was not a good thing to do and could have made gunk get stuck inside the carborator. But he float has been stuck or not shutting off the fuel to the bowl for a long time. Long before I added the two bottles of Seaform to the gas tank. The fuel level in the sight glass is all the way up and over the top of the round sight glass window. And this is with the truck running at idle speed. The needle is not shutting off the gas to the carburetor enough or maybe the return fuel line is plugges up too.

[fastboatman29212]

Sounds like you have a float problem. Maybe you have a hole in the float. Then the needle won't stop letting fuel into the bowl.

[Glenn Schoettlin]

Sounds like you have a float problem. Maybe you have a hole in the float. Then the needle won't stop letting fuel into the bowl.

I hope that's all it is and it's easy for the Nissan Mechanic to fix. Now if he has the parts on hand for a quick fix. I was thinking the same thing or else the needle value is sticking or has something stuck by it to not let it seat properly. But a hole in the float may be able to be drained and then plugged with some glue or something. I'm pretty desperate to get my truck running reliably this winter. I have an appointment to get it into the Nissan Mechanic next week on Tuedday. I'm keeping my fingers cross that he can fix it without keeping it very long.

I found that O'Reillys has a carb kit for this carburetor but it will take a special order and another 7 to 10 days to get the part kit delieverd to the local O'Reilly's store. I guess I can limp along until I get the parts and then reschedule the appointment later on this next few weeks.

[fastboatman29212]

I order from Rock Auto Parts all the time. New float is $4.60 plus shipping.
Link = http://www.rockauto.com/catalog/raframecatalog.php

[ArtDecodon]

I have a 1984 720 4x4. Will a 1983 carb fit on it? Same question for the Trans.

[fastboatman29212]

I have a 1984 720 4x4. Will a 1983 carb fit on it? Same question for the Trans.

I want to answer "yes" to both questions, but I have no experience with transmission swaps. Post the question as a new topic rather than in this topic and you'll likely get more views and better advice. This thread is about carb rebuild.

[RicardoGranados]

I haave read most everything I can find from you. I've read some of your trouble shooting advice but haven't seen anyone with the same issue I have. I just bought a really nice 1986 Nissan/Datsun 720 Z24 in perfect condition...body wise. Lol It cranks and drives but idols really high. And if given to much gas it stalls out then doesn't want to crank. Not exactly sure what it is but I'm thinking its carb related. Any idea?

[fastboatman29212]

I haave read most everything I can find from you. I've read some of your trouble shooting advice but haven't seen anyone with the same issue I have. I just bought a really nice 1986 Nissan/Datsun 720 Z24 in perfect condition...body wise. Lol It cranks and drives but idols really high. And if given to much gas it stalls out then doesn't want to crank. Not exactly sure what it is but I'm thinking its carb related. Any idea?

Before you adjust the carb, check for vacuum leaks in the lines. I think I measured about 30 feet of vacuum hose when I replaced mine. A vacuum leak would make it idle high. Spray carb cleaner at the base of the carb and see if that causes it to stumble of change RPMs. Spray the vacuum lines and see if any of them do the same thing. Let us know what you find out after checking the vacuum lines for leaks.

[RicardoGranados]

Well unfortunatly after a bit of trouble shooting I decided to take off carb for rebuilding. As I was dping so according to your instructions. Well...I don't think its the original carb. The further I went the more I found how rigged up it was. Trying to find the correct carb for a decent price. Nobody selling any around here and not trying to order a new one. Thanks for the info though.

[fastboatman29212]

Many folks switch to a Weber 32/36 and are very happy. They delete all the vacuum stuff. A Weber 32/36 is about the most affordable option. Check around for a used one at a scrap yard or get one new on eBay.

[sectionecho]

Lots of info here!! That is awesome! Let me ask you something about this carb. For some reason whenever I move the fast idle arm up the throttle goes to normal idle speed, but as soon as I press the gas the fast idle arm clicks up a notch and the throttle goes to 3000rpm. It will stay that way until I physically push the white fast idle thing down, then it will idle normally, but as soon as I move the throttle it jumps to 3000 and stays.. Any help would be greatly appreciated.

[fastboatman29212]

Lots of info here!! That is awesome! Let me ask you something about this carb. For some reason whenever I move the fast idle arm up the throttle goes to normal idle speed, but as soon as I press the gas the fast idle arm clicks up a notch and the throttle goes to 3000rpm. It will stay that way until I physically push the white fast idle thing down, then it will idle normally, but as soon as I move the throttle it jumps to 3000 and stays.. Any help would be greatly appreciated.

Sounds like the return spring for the fast idle cam is stuck or broken. Or maybe it just needs some lubrication.
Look at the Z24 Hitachi Carb DIY Rebuild Thread I made so you can get an idea about how the Fast Idle Cam works.
z24-carb-rebuild-diy-1984-86-t537596.html

Here are a few pics. There is a tiny thin spring that causes the cam to move back to the "slow idle" position.

[sectionecho]

Weird, I just bought the truck and the carb was just rebuilt, he had it sent off to get rebuilt, it looks brand new! I checked out the spring, you mean the one behind the plastic correct? The really thin one? It looks normal.

[fastboatman29212]

Check to make sure the spring is not broken. A rebuild kit does NOT contain a new spring, so it might be broken. If the cam does not spring back when released from other parts that touch it then that might be the problem.

[sectionecho]

Ok in that last picture it shows the fast idle arm with the little teeth pointed down..on mine the arm arms teeth are up more sticking on the little metal piece that is close to the 972 in your picture..is this what could be causing it? I could probably get you a picture.

[fastboatman29212]

Ok in that last picture it shows the fast idle arm with the little teeth pointed down..on mine the arm arms teeth are up more sticking on the little metal piece that is close to the 972 in your picture..is this what could be causing it? I could probably get you a picture.

The photo below shows a small bump directly below the teeth of the cam. (To the right of the arrow and above the yellow "r" in the word spacer.) That bump is what the cam teeth catch on. The photo shows the correct cam position at rest for a normal idle. It sounds like you are saying yours is rotated 90 degrees CCW. The cam teeth are NOT supposed to contact the "L" shaped cam stop that is close to the 972 mark.

The cam might NOT be the problem. All the cam does is hold the throttle butterfly open an extra little bit. It is giving the engine just a tiny bit more gas until the engine warms up. Then it stops doing it's job. Now, you made it sound like it was holding the throttle open. However, if the throttle linkage is being held open by something else, then playing around with the cam will be useless. Just keep that in mind before you take things apart that don't need to be disturbed.

[sectionecho]

Ok after further inspection, normally the fast idle cam is sitting like showed in the pic, but when you press the gas the little metal arm gets stuck over the hump at the top. Then if you push the top of the cam towards the drivers side, it will go back to normal.

[fastboatman29212]

Try removing the fast idle cam and see if it corrects the problem. That way you'll know if something else is sticking or if it's just the cam sticking.

[sectionecho]

If I remove the cam will it hurt anything to drive it like that? Other than it will not idle faster when first cranked?

[fastboatman29212]

It should not hurt anything.