Carburetor Help?

[AMC86Kid]

Hello guys i was wondering if anyone could give me any advice 

i am working on my 1986-2.8 L GM LR2 V6

when i bought the vehicle it came with a rebuilt 3.4 L L32 V6

it came out of a 1994 Firebird (From what i have read they are the same exact engine just the 3.4 is a larger version of the 2.8)

anyways it came with a carburetor and i got the motor to start and run a little but i can't get the carburetor to keep the motor running on idle 

they only way i can get it to run is by hitting the throttle over and over again 

is there any links or pics that can help me work on this carburetor i have never adjusted one before but i do have some basic knowledge on them 

i will try to post pics to so you guys could tell me what kind of carb i have Thanks 

[AMC86Kid]

Top Of Carb

 

 

Right Of Carb

 

 

Left Of Carb

 

[carnuck]

Was your original motor zero balanced? Some were. You don't want external balance stuff on the new motor because it can vibrate it to pieces. 

    Vacuum leaks can be an issue. Especially if your carb was for the heated base gasket version and not adjusted. Those carbs are notorious for issues too due mostly to age and modern fuels. I would try to find someone nearby who knows how to set it up and check for leaks if you don't know how. 

[AMC86Kid]

yes the 2.8 was externally balanced so i took the flexplate to a shop that zero balanced it for the 3.4

and the previous owner told me that the carb on it is either new or rebuilt because he wanted one that he could manually tune 

when i open it up and look inside it doesn't look dirty at all 

[Pete M]

this is probably not the right advice (I don't know carbs), but many moons ago with my old 86 I adjusted the idle screw to bump up the rpms. :)   (it's a little set screw that the throttle arm rests against at idle)

[AMC86Kid]

yes i have tried that but the carb looks a little more complex then just two or three screws 

it almost sounds like it runs out of gas 

i have installed a new fuel pump right by the fuel sending unit near the gas tank and checked if it shoots out gas from the fuel line that connects to the carb

it does but I'm not sure exactly if the fuel pump is just used to send fuel for a brief moment once you turn the vehicle on then stops 

or if its suppose to turn of and on momentary as the engine is running 

 

i have decided to wait until tomorrow to test it again because for some reason my motor is really hot and my radiator hose is very warm when you touch it also its has a lot of pressure to when you squeeze it not sure why its heating up so fast i only got it to run for about 8 minutes 

[Green Mesa XJ]

Honestly you are better off getting a Weber (dgs 38?) ,  what you got is a junk factory  carburetor. The adjusters are in the front center if I remember correctly you'll need a special tool to adjust it, had  difficulty finding one 20 years ago.

 

Easy to adjust the idle I think, but that may be the Weber I'm think of. 

 

I rebuilt that carb back when I first got the jeep, did a little better but the biggest improvement was the aftermarket carburetor.

 

check the base gasket for vacuum leaks,  just some carb cleaner sprayed around the base and other places you think it could be leaking. If you pull it apart to change the base gasket you can ditch the pre heater, it sits on top of the base gasket and plugs into the wiring harness. I've never seen one that works or didn't try to start a fire. Hopefully it's already gone.

 

if you going to keep the carburetor set up then upgrading the intake and carb will help a lot. Weber makes a carb. Holley does as well a four barrel, that goes with the  edelbrock 2 piece intake.   You can find them on eBay if you wait for a used one to pop up.

[Green Mesa XJ]

how is the catalytic converter? If the old 2.8 died of natural causes then it probably polluted the cat on its way out. 

 

BTW the oem fuel filter is at the back of the carb where the fuel line goes in, mine was frozen in place so I added a in line filter. 

[AMC86Kid]

so is there a way to tell what kind of carburetor i have ?

 

I'm pretty sure i have changed the fuel filter

from what i have read the 2.8 had a mechanical fuel pump that sat by the carburetor and pulled fuel from the tank to the carb 

i have put a new electricle one in line right by the gas tank so that it pushes the gas instead of pulling it 

 

i have took the vehicle to an exhaust shop and it has an entirely new exhaust

new pipes, new cat converter, new muffler  

 

i do not think the carb has any vacuum leaks 

and there is no wiring harness that it plugs into

[Green Mesa XJ]

To me if looks like the standard vara-jet 2se carburetor. They came in different flavors for computer controls and ac. 

 

Not a lot of options for the carburetor on this engine. Webber or Holley aftermarket is available. Factory set up was limited to the Rochester varajet..

 

far as fuel delivery, you need 4-6 psi (I think?)  to run correctly, not sure what that pump is rated or how it's wired because the 84-86 2.8 were mechanical fuel pumps. Most run a low psi pump and have a regulator in line to keep the pressure correct. 

 

If the catalytic converter is good and it should be, temps may be in line with hot summer day, dunno. Maybe take a temp in it with a laser temperature reader or a gauge if it has the correct  senser. 

 

 

[AMC86Kid]

here's the info on the fuel pump 

its made specifically for carburetors 

http://www.autozone.com/external-engine/fuel-pump/spectra-premium-fuel-pump/191528_0_5752?&searchText=E8016S

 

Can you send me a link for the correct Webber and Holley carburetor 

I can't even find the official Webber site and the Holley one asks for engine's cubic inches (not sure how to figure that out)

and for maximum RPM I'm assuming around 4600 since i have a 3-speed A904 automatic tranny 

 

Also should i get an electrical choke since its easy and regulates the carb automatically 

and should it have Mechanical or Vacuum Secondaries

[Jeep Driver]

I've not messed with a carb in 30 years, I have no intention to now either, so I cannot give you any specific advice. That said........

 

That carb is obviously designed for or around emissions, and it's a cluster-F, chuck in the trash where it belongs. 

 

 

I'd be looking for a 2 barrel Weber, nothing else. With a stock engine, you'll never get a 4 barrel jetted correctly. If you do go with a 4, you'll likely need a new intake, you'll be looking at $400 for a decent Edelbrock, and another $400 for a small Holley, 450 cfm or there about. Mechanical secondaries for sure. 

 

I scanned around last night and found nothing but a couple of S10 forums, nothing serious nor definitive regarding carbed 3.4

 

 

Call these guys, http://unitedspeedworld.com/ or Jegs or local speed shops in AZ, there is a lot racing out your way, you should have no problem finding information. 

 

One fuel line, one accelerator cable, and maybe one vacuum line........and........whatever you decide about a choke, cable or wire or.....that's it, keep it simple, it should look nothing like the cluster you have on there now. 

 

A good Weber is still going to run you about $450, I'm guessing, there won't be a cheap solution. 

 

 

Lastly, most, if not all, manufactures produce off-road versions, has to do with the way the floats are designed........make sure you ask if Weber has an off-road version of whatever carb you choose.

[Green Mesa XJ]

Tapatalk stoped wirkjng with this forum so it's kind of hard posting links. I may need to get on the laptop to post all the links.

BTW it all should be electric carduretors, I know the factory Chevy/jeep was. I don't know when manual choke died out but most 80s vehicles had electric choke.

 

 

there is a jeep Chevy Weber 3.8 DGSE kit, it's made for the s10 2.8 but works on the jeep. Comes with adapter plate to work on the factory  intake. Only thing is the bolt on the adapter plate for the air cleaner it too long for the jeep hood, I had to trim the bolt so it didn't dent the hood. They may have fixed this by now.

 

those run $375-400 on eBay I bought it much cheaper at another seller but that was a long time ago. Still I'd get the kit number and google search for sellers you might catch a break.

 

the  Holley is only for the four barrel adapter plate.

 

edelbrock 3785 is the intake base 

Edelbrock 3787 is the upper base for the factory and Webber carburetor 

edlebrock 3789 is the upper base for the 4 barrel Holly 

the Holley 0-8007 , 4160 390 cfm is the carburetor for the 4bbl kit,

 

all this stuff can be exspensive, but the edelbrock and hollley do come up on auction at eBay from time to time. I bought my intake upper and lower on auction for a good price. 

[Pete M]

chances are that you just need the existing carb adjusted.  just gotta find a local shop that specializes.  carbs are really hard to diagnose over the internet. :(  

[Green Mesa XJ]

The specs looks ok on the fuel pump, maybe a little low. I'll have to look up the minimum spec for fuel psi on the 2.8 later. 

[Pete M]

I have no idea how it should be, but it looks like I see one vacuum line plugged and another port open.  

[Marine1Texas]

The one that is open is the EGR. Looks like the cap off is to the EGR. EGR not opening is not going to be a issue unless smogged.

 

I would go with a weber 38 dgs. They are manual all the way but have auto choke. They run very smooth and easy to bump up sprayer size if wanted

[Green Mesa XJ]

The unpluged is EGR, which I'd leave alone unless you have to pass emissions. Even then it usually screws things up for running smoothly. 

 

the other plugged line with whatever that is I'll have to look up. 

 

Back of the intake manifold  is a splitter that goes to the break booster and splits off the the carburetor, I think, hard to remember this set up after all these years. I believe that rear splitter going to the carb is the most important but I need to look it up. It's a mess of lines for emission crap that didn't do much. Not even going to ask if you still got the AIR pump. 

 

Youre also missing some vacuum ports in the front of the intake some of the lines twould go a canister near the radiator drivers side. 

[Green Mesa XJ]

That carburetor like to be 4.5 to 5 psi. 

You might put a little gas or starting fluid down the mouth of the carb to see it if runs without going through the carb. 

Carb could be clogged jet, bad vacuum , or comthjng else. 

[AMC86Kid]

ok i see so i should get a carb with Vacuum Secondary since they are ideal for street vehicles with automatic transmission

and a 2 barrel carb is simple and easy to tune 

 

i have found the stamp that verifies its a Rochester Varajet II (i think the 2 stands for 2 barrels)

 

and i am not sure what this stamp is for but i was trying to figure out what exact model it is 

 

I found this website and clicked on "CK277" and it looks like the model i have 

http://www.carbkitsource.com/carbs/tech/Rochester/Varajet.htm

 

Also this looks like an electric choke so does that mean the the current carb is a

2 barrel / electric choke / Vacuum secondary 

 

[AMC86Kid]

Also will this link help me figure out where all the vacuum lines go on the carb

http://www.lunghd.com/Tech_Articles/Engine/2_8L.htm

[omega_rugal]

When it does idle, at how many rpms?

[AMC86Kid]

i can't really answer the question accurately because my RPM gauge does not work properly it goes all over the place 

if i had to take a guess i would say around 1000 to 1300 rpm

 

also in the pic that i was pointing 

can anyone tell me if that is an electric choke ?

[omega_rugal]

8 hours ago, AMC86Kid said:

i can't really answer the question accurately because my RPM gauge does not work properly it goes all over the place 

if i had to take a guess i would say around 1000 to 1300 rpm

 

that`s high enough, remember that a carb uses the intake air speed to draw the fuel, at idle the incoming air is so slow that an extra, smaller venturi is needed to work properly

 

if you keep pumping the pedal it works? mmm then the bowl has fuel and the accel pump works... are you sure the tiny fuel lines are not clogged? if you choke the carb with your hand does it keep running?

[Green Mesa XJ]

 
that`s high enough, remember that a carb uses the intake air speed to draw the fuel, at idle the incoming air is so slow that an extra, smaller venturi is needed to work properly
 
if you keep pumping the pedal it works? mmm then the bowl has fuel and the accel pump works... are you sure the tiny fuel lines are not clogged? if you choke the carb with your hand does it keep running?

Yeah, that idea is plenty high enough to keep running. As I remember it needs 700 rpm to idle. I'm going to get some pictures of my vacuum lines, there's a lot it looks like you are missing from the factory set up.

I'm leaning towards something clogged or poor fuel supply. Even if the previous owner bought a "new" carburetor it's been sitting for twenty or thirty years, things deteriorate in this time.


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