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Discussion Starter · #1 ·
Ok so I've been trying to tune this bad boy for a couple days now since it's finally summer and I've got the free time.

My question is this:
Isn't this the proper method for tuning??

Ensure that the choke is COMPLETELY open.
(I have something wedge in here holding open as such)


Then adjust the idle mixture screw.
(Screw in 2 full rotations to begin with)


Then back the idle speed screw out until it is not in contact with the throttle plate. Proceed to screw it in until it is in contact, and then 1 to 1.5 turns thereafter.


Then so long as the engine is running, adjust the idle mixture screw till it "sounds" right. Then adjust the idle speed to the desired setting.

So why is it that mine won't even run even if the idle speed screw is screwed in as far as it'll go?

The only way I can get it to run is if the choke is completely closed and even then it fluctuates up to 1500RPM no matter where it was, until it dies. So basically:
Start it up, 1700RPM, hit the gas to kill the fast idle.
Drops to 500RPM then rumbles up to 1500RPM, then drops to 400RPM, back up to 1500RPM. And so on until it idles too low on the lower portion and it kills itself.

Sooooo confused here guys. Also I put a few emissions items back on.


Any ideas?
 

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WEBER carbs can be "VERY" tricky to get set-up, "IF" your able to get it dialed in W/OUT an assortment of Jets I would be amazed..

If the eng won't run w/out the choke it's simply too lean..
You will need to change the IDLE jets (May be a Primary and Secondary) to get it to idle, and may also need to swap AIR Bleed Jet as well..

Dependent on WHICH Weber your running you may also have an ACCELL Pump Nozzle and of course for sure will have to find the correct size MAIN jet for your application..

Did a quick and dirty search and found these two links, one is for tuning the other for parts..

http://www.alamomotorsports.com/weber/jet_kits.html

http://www.racetep.com/webjettune.html

When I was running my DYNO Service I set-up a hundred MIKUNI's which can also be quite tricky to the unknowing.. :wink:
 

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Discussion Starter · #3 ·
So basically you're saying that there's nothing I can do aside from shell out the cash for a new set of jets?
 

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Unfortunately that is prolly going to be the case..
Keep in mind that fuel delivery is pretty much the life blood of an engine, w/out the fuel delivery being right (or damn close) your just chasing your tail..

Each carb circuit is designed to deliver fuel through a certain RPM and or Throttle Opening.. While each circuit can function on it's own at a very specific RPM at WOT they all pull fuel together.. If there is an ACCELL Pump it is designed to deliver X-Tra fuel when demanded like when you mash the gas..

Since you are unable to even get the eng to IDLE it's obvious there aint enough fuel available.. Even "IF" you could get the eng to Idle I doubt seriously you will get proper throttle response, mid range or WOT w/out swapping jets..

Oh, keep in mind that all the above is based on you NOT having ANY intake leaks and "PROPER" Fuel pressure... IIRC when I had the Duel WEBER Carbs on my Go-Fast VW I ran a Fuel pressure reg and set it up @ 4PSI..
 

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Discussion Starter · #5 ·
Fuel pressure should be as the doctor prescribed.
I tried both mechanical and an electric pump I had.

Here's what I'm dealing with:
 

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If the needle and seat are GTG ( IE: No trash in there), the float is in good shape, and everything inside is nice and clean then the carb itself should be fine..

A lean mixture will make it run pretty rough, when everything is dialed in and you bump the Accelerator your TACH should go to the desired RPM then drop back down to the correct/preset idle speed smoothly.. If it goes down below your set idle speed and then back up, or doesn't drop down it's either too rich or to lean in the idle circuit.

If your "SURE" there are NO vacuum, or Intake leaks then I think I'd take the carb apart, pull the jets and note the current sizes.. Once you know this info order up a couple jets for each circuit and try again.

You will need to note the "specific" TYPE of Weber carb you have so you can be sure you know each jets position and purpose. It should be pretty easy to find a parts breakdown for your Weber so you can get what you need.
 

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Discussion Starter · #7 ·
Sorry about that.
I've got the 32/36 DGEV

So if it's idling like that, would you think insufficient fuel flow?

Or is it flooding itself out?
 

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Audacity said:
The only way I can get it to run is if the choke is completely closed and even then it fluctuates up to 1500RPM no matter where it was, until it dies.
If it won't run unless the choke is completely closed,
then it's getting air from somewhere else.

Sounds like you have a rather large vacum leak.
 

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Discussion Starter · #9 ·
Hmmm you've got a really good point Selador.

Only problem is that I don't know where else to check!
Ugh. It'll be another early day of working on the Troop then...
 

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Just spent a couple minutes looking for tuning info I could post up.. This looks pretty good and may be helpful. http://board.marlincrawler.com/index.php?topic=45126.0

YES, as I mentioned earlier (couple of times) it's imperative that there be NO INTAKE, or VACUUM leaks. Either of these will make all your efforts pointless.

It's possible that the jetting is so wrong that closing the choke simply allows what little fuel there is available to be enough. Simple test (More air Less air test) is to increase or decrease the amount of available air to the carb.. If you restrict the air and it runs better then it's too lean, if you increase air and it runs better then its to rich.
 

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FNFAL308 said:
It's possible that the jetting is so wrong that closing the choke simply allows what little fuel there is available to be enough.
Makes sense.
 

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Discussion Starter · #12 ·
Removed it from the Trooper, I'll be breaking it down now.

Question though, is it safe to use RTV gasket maker in place of the little cardboard gaskets in between the spacers?




 

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I would not use RTV anywhere on a carb unless I had no other option..

I would get the carb apart and inspect everything very closely.. Note the Jet sizes and call REDLINE for some input on a good starting point for your jetting.. Order a rebuild kit, & gaskets when I order the jets to avoid the possibility of pulling the carb off again anytime soon..

In your 3'rd PIC, BTM/R is the Accel pump.. Prolly a good idea to "carefully" disassemble that to inspect the diaphragm.

These carbs are not terrible to disassemble but if you've never done one before you may want to take a few PICS as you tare it down.
 
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