AISAN Carb issues (1 Viewer)

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Hi everyone i recently purchased an 87 fj60 that has been desmoged, i feel it is very under powered, i dont have much power going up hills and at highway speed getting to 50 is a challenge 70 is not possible unless going down hill.
Initially i could barely get it in the driveway but after adjusting idle speed and mixture i dont get any stalls.
it idles perfectly and the engine runs smooth when in neutral and hitting throttle, 1st and 2nd gear feel good 3rd and 4th is where my low power seems to be
i put a vacuum gauge on and its stuck at 20"
im thinking that my issue is that my secondary on the carb isnt opening up, i tried the paper clip test and its been on there for a week with no movement
with the carb installed i can turn the throttle and then move the secondary and i am pretty sure i can see the butterfly move
could it be as simple as bending the lip that mechanically opens the secondary so that it opens more for vacuum to occur
any help would be appreciated, been spending hours tinkering and no progress
also im in NJ if there is anyone local
 

gregnash

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Have you been through the FSM? If not, there is a section on the Lean Drop Method that is a good place to start. If you are getting 20" at idle then you should be pretty good, especially if it is consistent. If you have tried the paper clip test on the secondary with no movement then it is definitely not working properly which would explain why it has a hard time moving.

If this is not a daily driver and can be down for a bit look up JimC (@FJ40Jim ) on here and hire his services to have your carb rebuilt for desmog (and maybe desmog the dizzy as well). Other than that, go through the desmog manual and ensure that everything is hooked up correctly as many times there are bad hacks, things not connected properly or small broken nipples that are allowing vacuum leaks.
 
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Thanks for the reply. I did the lean drop method to set th idle.
Is there a way to check the vacuum on the carb?
 

klinetime574

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If your engine is pulling 20” and failing the paper clip test, replace the secondary diaphragm and go from there. Should be able to swap it while the carb is still bolted down. Can’t remember if Toyota still has the secondary available. I know the diaphragm that comes in the Hygrade 791B kit needs to be bent to fit. I’ve done it once and that rig is running well AFAIK.

531D1F4C-5444-436A-9D71-1A1E87F99F6D.jpeg


Diaphragm arm on my carb, not OEM part but was correct. Can’t remember the brand on that one. Just know it was an orange box.

587D936F-C09B-4243-B086-FCC53A1E995E.jpeg


EDIT

Found some better pics to show what I’m talking about.

Hygrade in the diaphragm body with stock next to it

21F62FA0-A93A-4935-A840-CCD9FEAAC413.jpeg


Installed

C8508310-A9CF-4334-AD17-A42FE8370769.jpeg


See the blue sharpie mark on the new arm? Marked that to make sure to do the bend low enough on the arm to not interfere with the body.

HTH
 
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Thanks yup need going to store to get it, cant buy online, will let you guys know how it goes... Thank for the help!!!
 

OSS

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The secondary fuel circuit in the carb pretty much only is active when flooring the gas pedal. If the secondary fuel circuit is intentionally disabled on a properly working carb, you don't really notice it until you floor it and the car doesn't accelerate as quickly. When driving 65 mph on the freeway, the secondary fuel circuit isn't in use.

All that said, I don't think the secondary is the only problem with your carburetor
 
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i had found another post that said that linkage should have the small arm towards the firewall and the large towards carb, is that correct?

how would i test mech advance, if i manually hit throttle on one side i can open secondary with manual turning on other side and see the butterfly open, is their another way to test?

How do i test vac advance?

FYI the dist is a DUI HEI
 

FJ40Jim

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Yes.

Check mech advance wirh a timing light. Rev up engine and watch BB move down out of timing window, then come back when engine idles.

Test vac advance by applying vac to primary advance fitting on dissy. Should see breaker plate twist in CCW direction.
 
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buddy is going to bring me a timing light, can anyone confirm the timing, does it make a difference if it is desmoged
What I found is 7 degrees
Also I have hei dui distributor, does timing stay at 7 degrees I've read it needs 12 degrees.
Which is the correct port on the aisan carb do I use for vacuum advance?
 

gregnash

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Desmogged vehicles usually like a little more advanced timing but with the HEI dizzy that may be compounding things.
Again, look in my signature for a number of the documents we refer to, since your truck was previously desmogged and no knowledge on how well that was done it will be worthwhile to go through, maybe even replace the silicone vacuum lines (boostcontroller.com is what most use, or McMaster-Carr) as they may be stock 30yr old lines that have tons of cracks that are causing issues.
 

Seth S

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Are your valve clearances in spec? This won’t be a smoking gun but if they are out of spec they will have an impact. If you do need to adjust them you will have to do the lean drop again.

Small arm of carb linkage should be near the firewall. Long arm at carb.

I’ve driven my truck across country with no distributor advance, timing set at 7 degrees, all smog equipment in place, and as it turned out valves very far out of spec on the loose side and I was able to drive 65-70mph without much issue. Mountains were slow going but not a surprise.
 
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Tried to set the timing last night and never saw the bb when looking through the fly wheel window. Also the we couldn't advance the dui dizzy because it would hit a metal coolant hose, thinking this am that I can loosen the hose from the block so that I can advance the timing more. But can the timing be advanced or retarded so far that bb is not currently visible?
 
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After moving rad hose out of the way I was able to advance the dizzy enough where I can see the BB... How do I determine the degrees of advance below or above the needle?
 

gregnash

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You should see a small needle/arm that is sticking through the window from top down. If I remember correctly that is your set point for 7*. There is actually a line before the BB that when lined up with the needle would be 0* TDC. From there, if you dont have a timing light that tells you how far advanced you are, then it is kinda a guessing game to see what runs well and makes the truck happy.
 
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Thanks everyone, the timing was off, was able to find the line and bb, i had to loosen the radiator metal hose behind to set correctly, seems like previous owner and mechanics didn't take it off, will need to replace it with a rubber hose so that I can keep it out of the way.
Took it for a drive and felt a lot more power, smoother acceleration!
Just did lean drop method now will put paper clip back on and see if my secondary opens up.
Another question I have is should the vacuum hoses that come out of the pcv etc have clamps on or are they just push in? Currently there are no clamps.
 
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My Secondary is still not opening up, I read did lean drop and also adjusted the fast idle, i dont understand what the fast idle does, is it to set the idle when you pull the choke from inside the cab or does it also affect something else on the carb?

last few days that its been colder(55 degrees) noticing that it runs rough until it gets up to operating temp

i ordered parts to make a smoker to see if i can find a vacuum leak, all the hoses look good

I should get my secondary diaphragm tomorrow

if i cant find a vacuum leak and the secondary diaphragm doesn't make a difference, I am thinking of ordering a 38 webber carb, any thoughts?
 

klinetime574

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@moyafj60 don’t buy a Weber.

Replace the secondary diaphragm, and if that does not work then you’re due for a carburetor rebuild. Probably wouldn’t be a bad idea anyway if you don’t know the last time it was done. Some of the small passageways could be plugged.

The diaphragm is very thin rubber, its probably cracked, and therefore not holding vacuum.
 

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