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 Post subject: '84 B2000 carb problems
PostPosted: Tue Jan 26, 2010 3:11 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
Hello forum!

I have a 1984 Mazda B2000 I've been driving for about a year now. Now that winter is upon us, I thought I'd rebuild the carb and adjust the choke to make it easier to start in the cold.

I have the carb back together, and I also took off all the EGR and smog stuff (I'm exempt from emissions and it wasn't working anyway). I made a blockoff plate for the intake manifold and I blocked the exhaust fitting off by removing the EGR pipe and putting a nickle in the fitting. :mrgreen:

The problem I'm having is that I can't seem to get the carb to tune right. If I were to describe all the symptoms it would probably sound like a vacuum leak...

1.) Won't idle below 1000 rpm
2.) Idles and revs smoothly in neutral
3.) Loses all power above 2000 RPM in gear
4.) Won't run unless the mixture is rich
5.) Won't run unless the choke is almost completely closed, even at operating temp.

The part I don't get is that my vacuum gauge shows 20lbs of vac. I also tested it for vac. leak by spraying starting fluid around the manifold and vac. connections, it didn't seem to effect it any, so I don't think its a vac. leak.

And I thought it might be that the spark isn't advancing, but the timing seems right and it is advancing. I recently replaced the cap, rotors, wires, and plugs, and I gapped the plugs to spec.

I have no idea what my problem might be, I am going to check for fouled plugs tonight, other than that I'm at a loss... it was running OK before I rebuilt the carb, but it didn't want to run right until it warmed up.


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 Post subject:
PostPosted: Tue Jan 26, 2010 4:19 pm 

Joined: Sun Jun 01, 2008 9:13 am
Posts: 70
Location: Vancouver Canada
I would look at 3 things to start

Fuel pressure
Float adjustment/needle and seat are correct
Idle jets and paths are clear

Good luck

J

What you have described sounds like fuel starvation to me.

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 Post subject:
PostPosted: Tue Jan 26, 2010 9:40 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
I checked the float adjustments and it was off a little, so I adjusted it to the specs from the rebuild kit. I noticed that the fuel is pooling up to the line in the float bowl now, before it was a little under.

I was also thinking that I had mixed up the jets or something, but I checked it again and they were all in their proper place. The jets are all numbered so it was easy to identify what went where.

I am sure that the idle jets are clear as I sprayed all the jets and pathways out with compressed air when I rebuilt it.

I also noticed that the linkage for the diaphragm on the secondary was loose, I missed putting the e-clip in it before. So I replaced the e-clip. The secondary should work now, in theory.

After all this, I put the carb back on and its still having the same problem. It seems like the secondary is not kicking in for some reason.

I'm thinking of taking it to a mechanic if I can't get it straightened out soon. I've been taking off from work so that I can work on it when its warm/daylight outside. But I can't afford to miss much more work.

:lol:


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 Post subject:
PostPosted: Wed Jan 27, 2010 6:47 am 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
So I brainstormed a little more today, and I'm thinking maybe I have the linkage for the secondary wrong. I've tried it in several different configurations, haven't had much luck with it in any of them.

Does anyone here happen to have a pic of the B2000 Nikki carb linkage, particularly where the secondary connects? I should have taken pictures before I started tearing it apart :roll:


My other thought is that maybe I'd be better off buying a Weber than having a mechanic tinker with the stock carb. A Weber is something I'd like to do anyway, it'd be nice getting a bit more power. It is my understanding that the Weber 32/36 would probably add a little more economy as well. I'll have my taxes back soon so now is as good of a time as any.


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 Post subject:
PostPosted: Wed Jan 27, 2010 8:41 am 

Joined: Sun Jun 01, 2008 9:13 am
Posts: 70
Location: Vancouver Canada
One more question

Look down into the venturies ,with out the truck running open the throttle to wide open,Do you have fuel squirting out the emultion tubes when the secondarys come in? or at ant point ?

j

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 Post subject:
PostPosted: Wed Jan 27, 2010 9:18 am 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
I don't think the secondary throttle plate is even opening, it seems to be vacuum activated. I will try to see if any gas comes from the emulsion tubes though. Are the emulsion tubes the ones that are on the boosters and angle down into the venturi?

Is there a preferred vendor for Weber conversion kits? I am sure thats a common topic on this forum so I'm about to do a search.


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 Post subject:
PostPosted: Wed Jan 27, 2010 10:44 am 

Joined: Sun Jun 01, 2008 9:13 am
Posts: 70
Location: Vancouver Canada
Yes the exit of the emultion tubes are in the center of the venture, If your secondarys throttle flaps are vacume acuated the accelerator pump should still be squirting fuel down the primarys as you acelerate aggressivley.

Check with the truck running if the secondarys open when requested.

Check for fuel squirting out the emultion tubes.

Sorry i can`t help with a webber vendor.They should be ready available at any auto parts retailer i would think.

J

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 Post subject:
PostPosted: Wed Jan 27, 2010 1:52 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
I found a couple of vendors for the Weber kit. They seem to be going for about $350, which is a steep chunk of change but still about even with the cost of a re-man stock carb.

I'll tinker with the secondaries when I get home tonight.


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 Post subject:
PostPosted: Thu Jan 28, 2010 1:40 am 
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Joined: Thu Mar 12, 2009 6:45 am
Posts: 71
Location: netherlands
Maybe this can help you?
mazda carburator training manual

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1977 mazda 818 1.3L 8V coupe
1992 mazda MX-6 2,5L 24V

www.dutchmazda818.nl


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 Post subject:
PostPosted: Thu Jan 28, 2010 8:11 am 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
mazda 818 wrote:
Maybe this can help you?
mazda carburator training manual


That did help a lot actually. I think it could be that I have the linkage for the secondary wrong. I didn't get a chance to look at it last night to see if the secondary was actually opening but hopefully I will tonight.

That carb manual is much, much better than the Haynes manual I have been using, or the instructions that came with my carb rebuild kit. I actually took the Haynes back to the store last night.

I suppose I'll spring for an actual factory service manual once I get my tax refund. :mrgreen:


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 Post subject:
PostPosted: Sat Jan 30, 2010 7:31 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
I ordered a Weber kit yesterday and it should be here sometime next week. I am thinking it will be good just to slap on the Weber because it seems pretty plug-and-play. Should be an upgrade in both mileage and performance too.

I think when the weather turns warm again I am going do new gaskets on the timing and valve covers, and a new oil seal for the distributor. I seem to have an oil leak or two somewhere. :?

I also read something about upgrading the rocker arms for better valvetrain oiling, which I might do as well because I have a little bit of noise coming from the valvetrain.


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 Post subject:
PostPosted: Sun Jan 31, 2010 1:13 pm 
JNC Fanatic
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Joined: Sat Sep 13, 2008 9:10 pm
Posts: 1381
Location: Boston, Assachusetts
Any pics of your pickup? :P

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1981 Toyota Te72 Corolla
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 Post subject:
PostPosted: Mon Feb 01, 2010 1:25 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
I'm working on getting some pics, probably once the carb goes on.

Its nothing particularly special to look at right now though. The good thing about it is that it is rust free and the body is kinda straight. It started out life as an auto, but the previous owner swapped it to 5 speed. I had to swap to the right pedal cluster and do all the little odds and ends to finish the job. :lol:

The bad about it is that the wiring is fubar. The stereo/accessory wiring is all mucked up and the fusebox has been replaced and they just spliced one in using crimp connectors. And its reaching the point where things are about to start wearing out. It also has an Earl Schibe paintjob that I don't particularly care for. :lol:

I did convert it over to some factory buckets I found at the junker last year, and I have pics of that...

Image

Image

Image

Once I get the carb situation sorted out, I'll probably start on the interior. I already swapped out the blue dash for a black one, hopefully this summer I'll be able to re-do the door panels in black and find a decent black carpet set. We'll see. :tu: [/img]


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 Post subject:
PostPosted: Mon Feb 01, 2010 1:35 pm 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
One other thing about the truck is that I don't care for the Grant steering wheel because it just looks chintzy. Would it be possible to fit the steering wheel from an RX-7 onto my column? Maybe something like the one in this pic?

Image

[/img]


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 Post subject:
PostPosted: Mon Feb 01, 2010 2:10 pm 
JNC Fanatic
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Joined: Sat Sep 13, 2008 9:10 pm
Posts: 1381
Location: Boston, Assachusetts
I love that style of Mazda/ Ford Courier pickup. You don't see them around anymore. :(

Something cool about lil Japanese RWD pickups that makes em fun.

About the RX7 steering wheel fitting.. it should fit, because most brand steering wheels do fit across the board. It would also help if you can get or have the original RX7 hub to mate to the RX7 steering wheel. Although, your hub may fit it. Good luck. :wink: :tu:

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1981 Toyota Te72 Corolla
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 Post subject:
PostPosted: Tue Feb 09, 2010 10:46 am 

Joined: Tue Jan 26, 2010 2:52 pm
Posts: 11
Location: Athens, GA
So I bought the factory workshop manual on E-bay and its much, much better than the Haynes manual.

The factory manual has several complete wiring diagrams, shows where the harness routs, etc.

It also has detailed pictures and procedures for the disassembly and re-assembly of the carburetor. :tu:

I put the Weber kit on the other day and the truck ran decent with it right out of the box. I've been working with tuning it to try to get it to run even better. Now that I have the manual and the detailed procedure for setting the ignition timing, hopefully I can get the most out of it.

I am thinking I might go back over the stock carb and maybe put it back on after the spring thaw and then use the Weber on my other project vehicle, a 1962 Ford Falcon.

The one problem I am having with the Weber is that the linkage rod for the fast idle is cheaply made. It is secured to the rest of the linkage by a bent tab (rather than by e-clips) and keeps coming loose and getting stuck in the throttle linkage. I may try to custom-make a fast idle rod that uses proper bushings and E-clips by finding one thats close on a different carb and bending it to a shape that will work.


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