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PostPosted: Sun Oct 04, 2015 3:01 pm 
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Location: Palm Springs, Calif
From your first cigarette, to your last dying day.
And so the song from West Side Story begins.

Carburetors have jets.
Jets are one thing which make carburetors different from fuel injected cars.

MK1 carburetor cars in the USA used the Hitachi carburetor, and it was the last time Suzuki used a carburetor, switching to fuel injection in '89.
The carburetor cars of '85-'88 have some pretty good fuel economy and very low emissions.

A while back I was looking through the junkyard at an old Chevy Sprint and saw this carburetor:
View A
Image
View B
Image
View C
Image
and
View D:
Image

I snagged it because it was so CLEAN.
Rarely do you find one that clean on a junkyard Sprint.
Who knows, it might be a good one or so I thought at the time.

It has been quite a long time since I rebuilt a carb and thought it might be interesting to take one of the old carburetors I snagged in the junkyard, and simply bolt it on and go.
Plug and play, if you will.
What could possibly go wrong?
I read on the forum all the time about guys swapping junkyard carbs on their old cars and fixing all sorts of problems.

This carburetor had a few parts missing, so I knew I'd have to swap a few parts from my current carburetor to make it work.
It sure looked clean...almost like the guy had put a rebuilt carburetor on the car and then junked the car.
Or else it was a professional rebuild and I had really scored a great deal at the junkyard.

Time to take a closer look.
First, I pulled off the top and removed the accelerator pump:
Image
I'm no expert, but there's a chip out of the pump on the right of the picture.
Not a deal breaker.
The car would still run.
Might not accelerate as great as a new pump, but that's life.
What do you expect for $25.
Dock it one star, if you will.

Next, I checked the float valve.
Probably due to sitting for a few years, the float was stuck shut.
It might have freed itself, and then again, maybe not.
This would certainly be a deal breaker.
You go to all the trouble to bolt on this junker, and no fuel.
A real piss off.
Dock it another star.

But you'd have a heck of a time diagnosing it, because it looks like the fuel/air level in the carb is fine.
Why?
Image
The rubber O-ring behind the sight glass wasn't in correctly and you would see a black line through the glass.
I can't see how it wouldn't leak.
That probably was one of the cars here where a guy wrote in and said, "I just installed a freshly rebuild carburetor. It runs fine, but boy do I smell gas!!!"
For me, having spent hundreds of dollars on a rebuild, and having a tremendous fire potential on the road would certainly cause me to either take it back to the mechanic or junk the car.
Imagine a tiny O-ring like that causing an owner to junk a car. It happens.
Dock it ANOTHER star!

Now, let's look down the accelerator pump body.
We've pulled the accelerator pump, and the retainer spring, but the stainless check ball at the bottom?
She's stuck!
Take a look:
Image
The check ball looks like Saturn with a ring of varnish holding it in place.
This would certainly screw with a guy trying to mash down on the gas pedal.
Dock it another star.

Screws in the wrong places, screws which don't belong on a carburetor:
Image
gaskets reversed, internal springs completely missing, but he did a NICE job soldering the MCS in place.
Let's give him one star for that.

At this point, it looks like the carburetor isn't a plug and play situation after all.
But at first it was OH SO TEMPTING.
I'm glad I didn't try to bolt it on and live with it.
Nope.
I don't recommend you use junkyard carburetors without rebuilding them first.
There are so many things that can go wrong, if you read a thread and someone tells you he installed a junkyard carburetor -
RUN!
:lol:


Are these carburetors that complicated?
Or is it so easy a CAVEMAN can do it?

Stay 'tuned'.
:wink:


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PostPosted: Mon Oct 05, 2015 1:00 pm 
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My first thought was "it sure looks minty!"
Till I read the post.

Good post btw.


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PostPosted: Thu Oct 15, 2015 8:25 am 
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Location: Palm Springs, Calif
Correct.

This carburetor looked SO beautiful on the car.
And the car, even in the junkyard looked like it had been well kept by the owner.
The engine wasn't the cleanest, but that carb sure stood out.
I was SURE it was a winner, but was I wrong.

Now, let's take a quick look at that float level sight glass area again.
Here's a view from the top, inside.
You are looking as if you have the top of the carb off and you are standing on the left side of the car:
Image
I'm not sure if the Photobucket picture has enough definition, but that O-ring has definitely jumped out of place and that would cause a SERIOUS gasoline leak.
If we look through some old threads in the MK1 section, we'll probably find out who's car it was.
"I just rebuilt my carburetor and now I smell gas..."
"I just installed a rebuilt carburetor and now it smells like gas, HELP!!!"
Etc.
:lol:

Although you may have heard the term 'bowl vent solenoid' several times on Teamswift, you might never have seen one.
Here's the one which was on the carburetor; the screwdriver is pointing at it:
Image
It looks fine, but there's one huge problem.
It is missing the plunger, spring and a couple of O-rings.
Here is what it should have:
Image
The bowl vent solenoid (BVS) specs out with an ohm meter, but when I put the plunger in, and the unit on the carburetor, I wasn't able to see the plunger work properly when 12 volts DC was applied.
As they age, they can get hot on long journeys; perhaps this unit no longer works?
I'm wondering if the guy figured it would be best to remove the plunger because it didn't work?
What does the BVS do?
When you shut off the car, it seals up the gasoline portion of the carburetor so that the gasoline doesn't evaporate.
That means your carb won't dry up if you leave it sit for a long period of time.
Is that a good thing?
Certainly. It is a HUGE improvement over the old dual pumpers which are vented to the atmosphere and dry out if not driven daily.
The BVS can prevent the build up of varnish inside the carb.
You can see the heavily varnished check ball in the accelerator pump in the picture earlier in this thread?
Removing that plunger may have contributed to that.
Later we can take a better look at this.
If there are any newbies in the audience at this time, they might be paying attention and learning the virtues of the 'emissions cr*p'.
It's actually really good stuff.
Also, with the BVS functioning properly, the gasoline won't evaporate, so cold starting or starting after it has been sitting for a couple of weeks won't be so difficult.

"I just put a rebuilt carburetor on it and it runs like sh*t!"
How many times have we read that in a thread?
We generally take for granted (assume) that the carburetor was rebuilt properly.
What could possibly go wrong?
Ha!
That phrase was repeating itself in my head as I took a closer look at this super clean looking carburetor.

Now let's look at the body of the carburetor.
This is the 'meat' of the unit.
It's what has all the little passages and what usually gets the attention during cleaning.
I've circled an area in red:
Image
For orientation purposes, you are looking at the Hitachi DFB 306 from the right side of the vehicle.
Closest to you is the bowl, where the gasoline is kept at a certain level by the float/valve assembly and the Mixture Control Solenoid (MCS) sits.
On the left, that hole is for the accelerator pump.
The next hole, circled in red, is the outlet for the accelerator pump and it dumps into the primary venturi.
Last, you have the venturi on the right, farthest from your view where the secondary opens upon hard acceleration.

Now that we are oriented on the picture, let's get an idea of what happens.
You step on the accelerator, the pump puts a small amount of gas into that hole circled in red, and the primary venturi sucks it into the engine.
Simple enough.
INSIDE that hole circled in red is supposed to be a check ball which is under slight pressure, keeping the accelerator pump area full of gasoline in case a small shot of gasoline is needed.
Here is what is supposed to be there:
Image
From left to right:
-check ball
-brass weight
-spring
-brass weight

Upon disassembly, here's what I found:
Image
-check ball
-brass weight
Our rebuild Dumbo probably lost the two parts, didn't see the need to replace them with new ones or couldn't find some and figured no one would find out.

Would it run?
Certainly.
Would it pass an emissions test?
Nope.
That would be a favorite place for a tech instructor to rearrange during a final exam, no?

What would be the consequences of not including the other weight and spring to the rebuild?
I'm going to go out on a limb and guess that a negative pressure would be created in the chamber by the primary venturi.
Your engine would suck a certain amount of gas constantly from the accelerator pump area.
You'd have a heck of a time, because at idle, there wouldn't be enough vacuum to suck that gas out of the accelerator pump.
So you'd adjust everything at idle and she'd be fine.
As soon as you opened it up about a quarter throttle or more, the engine would start sucking gas not originally intended by the designers of the vehicle.
It would have a rich mixture and your HC would be high during a smog test.
There's one for you.
Leaving out two tiny, almost inconsequential parts would cause a car to fail smog.
Now I see why a lot of bumpkins hate smog testing.
They can't rebuild a carb correctly.
You, after reading this web site, certainly can.

Here on Teamswift, we try to help people with their cars.
Unfortunately, we cannot consider all possibilities with some vehicular problems.
A guy who posts something like, "I just put a rebuilt carb on my car and it is worse than before!" doesn't realize he's created the problem by introducing faulty parts to an already disabled vehicle.
We, trying to help, are only as good as the information you supply.
So don't pitch a bitch when we ask for pictures and videos of what you've got.
You bead blast a carb body and make it all nice and shiny, but you don't know what you are doing when you rebuild these puppies and you're creating bad blood between you and the end user.
These are not your 650 cfm dual pumper Holleys of the V8 era.
The electronics are there for a reason, as are the vacuum servos.

I've had people tell me they would rebuild these carburetors better than original and post how to threads with plenty of pictures.
They blow hard and even get some people to believe in them and send them their carbs for rebuild.
A year later? Carb still in a box somewhere, not rebuilt, waiting for us to post threads like this so they can rebuild it.
So that's why I'm a bit slow in posting this thread...I don't want to steal their thunder and I'm always willing to learn, especially if they know better than the factory.
A couple of guys have contributed enough information on how to rebuild these, so this thread is probably redundant, but at least you see a few problems which arise when people try and think outside the box with the Hitachi.
It is a simple unit, if you take it one step at a time and understand why each little part is important.
If you look at the whole unit, it might scare you.
Don't make that mistake.

In general, my threads try and take seemingly complicated things: installing wheel bearings, rebuilding transmissions, balancing engines, etc. and making them somewhat simple.
You won't find any "only I can do this" kind of crap in them.
If I can figure out how to do it, you can too.

When I joined Teamswift I didn't know squat about Hitachi carburetors, etc.
The people here have a wealth of information which can be applied successfully to many car platforms.
Work safely, and consistently.
You'll save a lot of money by doing the work yourself.
But be prepared to ask questions rather than continue in your ignorance and screw things up totally.
That's how you'll learn.

People who rebuild carburetors for a living do it well and much better than me.
They are at a disadvantage in only one area, and even that it a limited one.
I have an MK1 to put the carb on and run it through emissions testing to make sure it is right.
That's why the carb rebuild people prefer to set up a carb on an actual car.
They have the emissions testing equipment to see what comes out the tailpipe and thus know their work is properly installed.
They do their best, but can only do so much if the carb is to be installed on a car out of State, for example.
It is very hard to provide a warranty on those items as you don't have a clue what the end user has done with your work.

These carbs are designed to work with a specific set of variables.
An ECM (not the newer PCM), no throttle position sensor (older type unit) and vacuum servos which are tied to the exhaust (oxygen sensor).
That's why I find it interesting that someone can build it better than factory, or so they claim.
I've been waiting to see how they'll do it.

There was a guy here (Geostalker) who needed help with these carbs a while back and I posted the needed help in his thread.
He runs over to GMF and calls me an idiot. Literally. In capital letters. Yep.
I called him out on it. (He asks for help, I provide the information and he calls ME the idiot?)
Never apologized. Instead said we were 'okay' now.
WTF?

Later, he had a problem with the adjustments after buying a 'rebuilt' carburetor.
His 'mechanic' wasn't able to solve the problem. (It was an idle up adjustment - very easy to solve.)
Son of a gun if I forgot to chime in and tell him what he was doing wrong. :owned:
Two years later and he's selling the car and it still has the same problem.
So who's the idiot?
He's been so busy posting on the forum he never learned what he was doing wrong and he's going to pawn his lousy work off on someone else?
Good luck with the sale.

Another odd ball story -
A few months ago, a guy asked me if I rebuilt carbs and how much.
I asked the guy if his car ran and he asked me 'what has that got to do with it'?
Obviously it has a lot to do with it.
If the guy can drive the car to my place, and we can set up the carb correctly, he will have something for his $400 carb install.
Apparently, he was thinking outside the box and had removed the oxygen sensor, etc.
Now how could you get a feedback carb to run right with all that removed?
Then he goes bitching how I can't build a carb? I don't think so.
The point is - you've got to have ALL the systems working together to get the best mileage and longest life out of your engines.

Enough of the rants.

With all the carburetor rebuild failures, there are many more successes.
Once you get them dialed in, if you drive them properly, they will give you excellent results.
All this carb information was taught to me, and if I can learn, so can you.

BTW:
Has anyone done a thread on accelerator pump rebuilding?
I'm sure the Teamswift member who claimed he can "rebuild the carbs better than factory" would know.
Does anyone remember that masked man?

If you've read this far, and remember... a video/photo shoot on how to rebuild an accelerator pump for these Hitachi carburetors is a post worth saving on the site for future use.
Accelerator pump rebuilding is a dying art.
How many people you know can do it without destroying the hollow brass reed?


Last edited by pacapo on Fri Oct 20, 2017 12:46 pm, edited 1 time in total.

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PostPosted: Fri Oct 16, 2015 1:42 am 
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I doubt there are any of you still following this thread, but we'll add a bit of blah blah blah to an already blah blah blah-ish boring thread on carburetors.

We've talked a lot about 3 solenoids in the carburetor.
In this post, you'll be able to see 2 of them in action.

First, the bowl vent solenoid.
For orientation, let's look at the fuel bowl again:
Image
It is the (mostly) rectangular cavity nearest you in the picture above.
There is a cover which fits over it and keeps you from smelling gas fumes normally.
If we could shrink ourselves to a size that fit inside that bowl and looked up at the cover, that is the orientation of the 10 second video below:
(click to view)

Image

As we energize the solenoid, the electromagnet pulls the plunger back and vents the bowl so that the fuel can enter the engine and air (and fuel vapor) can occupy the top half of the bowl.
This is what happens automatically when you turn on the key and the engine fires up.
It might be interesting to consider what happens if that plunger won't retract and allow fuel vapor from the charcoal cannister and air from the air horn into the fuel bowl.
For now, you can see how it works.
I put a little EZ Turn lubricant on the plunger because it is resistive to fuel and fuel can sometimes soften the plunger seat and cause them to stick shut.
Now it is working normally.
This carburetor was definitely not plug and play!

Last, let's cut to the chase, or look at the fuel cut solenoid.
In this video, also only about 19 seconds, you can see how easily they work.
It is basically the same as a bowl vent solenoid with a few minor changes.
First, the plunger is metal.
Second, O-ring has been moved to the area where the solenoid bolts to the carb body.
Take a look at the fuel cut solenoid (removed for easy visualization) and see how responsive it is:
(again, click for a 10 second video)
Image

The purpose of the fuel cut solenoid, as mentioned many times on this site is to shut off the fuel to the IDLE CIRCUIT when you turn off the key.
Dieseling, or a condition where the engine continues to run on its own compression when hot may occur if this solenoid isn't present or has been disabled.
This fuel cut solenoid (FCS) is a part which seldom goes bad and seldom gives a mechanic problems.
Unfortunately, it is often classified as 'smog sh*t' and looked at with disdain by bumpkins.
Is there any down side to a FCS? Not really.
Are they a good thing to have on a carburetor? Absolutely.
It adds expense and some complications, but there is a reason it is installed.
Now you've seen one in action and they are very responsive, like the BVS.

That covers 2 of the 3 solenoids on the carb.
The MCS has been covered a lot by mkc1962 and glacierburst.
Let's confine this post to the BVS and FCS.

The two solenoids are now working in this super clean carburetor.
I've mentioned a few hazards you can encounter with a supposedly 'rebuilt' carburetor.
This carburetor is a LONG way from being ready to bolt on, but what has been posted in this thread so far will probably help that clown hiding out there who can rebuild 'em better than factory.
We figured out who he is yet?
Hint: He's not posting any DIY threads lately.

Next post I may talk about the base.
How does that song go?
"It's all about the base, 'bout the base, no trouble..."

Until then...
:mrgreen:


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PostPosted: Sat Oct 17, 2015 8:05 pm 
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outstanding post. with fantastic pictures :worship: :worship: This is the reason why pacapo is an asset to our community.
we have had our differences, but for all his grumping, I still look forward to reading his posts, because I always learn something I didn't know. well done ,Jonathan

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PostPosted: Sat Oct 17, 2015 8:37 pm 
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Prairie to Pine Co. wrote:
outstanding post. with fantastic pictures :worship: :worship: This is the reason why pacapo is an asset to our community.


Well said X 2 :D
I do not always post but I always read pacapo posts to learn something :D

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PostPosted: Fri Dec 11, 2015 12:53 am 
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Although I had intended to talk about the base, for now a little update.

The above carburetor had serious issues.
-improper float level
-sight glass leaks
-improper assembly
-caramel like substance in the bowl and accelerator pump from sitting for years.

It was cleaned, the issues repaired and installed (finally) today.

The car now has the same acceleration as before, but no hesitation over 70 miles per hour.

Here is the carburetor which was pulled from the running car (center):

Image

The center carburetor has an issue with the bowl vent solenoid.
Probably from almost 10 years of use, there is a sort of gum which has formed on the bowl vent plunger.

So the electronics are still good. A simple cleaning of the bowl vent solenoid and it could be put back into service.

That's the update for tonight.


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PostPosted: Tue Apr 26, 2016 11:11 pm 
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i would SOOOO drive down and hand you $400 bucks to watch you do my carburetor and LEARN! Thank You for the excellent technical material and all of your consistant help!


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PostPosted: Thu Oct 19, 2017 11:29 pm 
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This has some great info. Do you guys have a suggestion on how I can view the photos on this thread?


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PostPosted: Fri Oct 20, 2017 11:30 am 
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weallknownada wrote:
i would SOOOO drive down and hand you $400 bucks to watch you do my carburetor and LEARN! Thank You for the excellent technical material and all of your consistant help!

Just saw this post.
My Mom is from Martinez.
Small world.
Too bad there are not more people with your interest in the world.


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PostPosted: Sat Oct 21, 2017 5:19 am 
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Swifteee wrote:
This has some great info. Do you guys have a suggestion on how I can view the photos on this thread?


I'm seeing them, and I see they're photobucket links. Photobucket did something mean a couple of months ago, trying to grab some money. If you google "photobucket fix" you should see plugins that you can add to your browser to work around this issue.

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