Weber Carb Help Needed - Long (1 Viewer)

Joined
Oct 8, 2003
Messages
462
Location
Near Junk
I am finally getting my 07/'76 FJ40 road worthy. Last step seems to be Weber carb tuning. Yes - I've read searches here for the past few days. Yes - I have the weber carb site which basically just tells you how to set idle mixture and idle speed. Need some extra help though.

I have de-smogged 2F with Weber 38DGAS and headers. eChoke is on it and seems to be operating properly (choke closes when started then opens when warm - does this fine after warn start also). Truck has been sitting alot for past 18 months or so during rebuild. Ran great before rebuild. Note rebuild was for a new Aqualu tub and did not involve any engine work. Now get stumbling and small backfires at high revs and under load (like when you floor it or trying to accelerate at low RPM like in 2nd gear. Note it idles fine - no issues with that.

Vacuum at idle is around 17 with slight 1-2 pt fluctuation (meaning I may need to re-gap my plugs - no big deal). Dizzy looks good and no cracked cap or any bad wires. Fuel pump is giving me about 4psi so no worries there. Brand new OEM fuel filter in it - old one cut open looked good with no rust or particles in it. I bought a fuel pressure regulator to hook up as I read Webers like 3psi going in but it ran fine before sitting for 18 months with no regulator so I don't think that is issue. Checked fuel filter on the weber and that is clean also (wasn't clogged at all or sludgy).

I can't imagine timing would change since it ran well before and no real use since sitting for a while and distributor was not pulled or changed. I can check that though tonight. Same comment on valve clearances though I can re-set them if people think they could change while the truck basically sat idle (I am no expert here so let me know).

All this leads me to believe possible bad accelerator pump or clogged port there. Any ideas how to test this on a weber? I ordered the Weber HP Manual and hope that can help but its days away and winter is coming. I was about to take the carb off and soak it but thought I'd check here first for other suggestions to rule out the obvious.

Oh - I SeaFoamed it yesterday and it didn't smoke much after waiting 5 mins and restart. Also tried the choke cleaner trick where you spray it in the main body with engine running and then choke off air to create greater vaccum to try and pull free clogged jets/ports - that didn't seem to work either.

Appreciate any thoughts (besides throw the Weber away). I am convinced I can get it to work and my previous 40's stock Aisin was no joy to tune either for this carb noob so be kind.

AndrewT
 
Last edited:
Joined
Apr 22, 2004
Messages
1,502
Location
Johannesburg, South Africa
 
 
 
Webers are easy to work on and very reliable too, I have never had any real issues with the one I had on my 40 and the 38/38 I have now on my 60.

How does it run at speed? Backfiring out the carb or out the exhaust? Or is it sputtering?

I had mine spit and sputter when accelerating but idle fine after putting it on. Turns out some bonehead (that means me) screwed up and installed the float wrong. I took the top off, reinstalled the float and adusted it and have no problems since.

HTH
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Thx. When you said 'take the top off' - did you mean taking the air cleaner off or also removing that plate that is under the air cleaner?

It was backfiring out the exhaust yesterday though I just started it and it was backfiring out the carb now when I reved it (before it was really warmed up). I have the schematic from the web but it only numbers the parts and doesn't tell me what they are. Fawkers.

AndrewT
 
Joined
Jan 26, 2005
Messages
4,874
Location
in the garage
have you had the same gas sitting in the tank for the last 18 months?

find your self some BG products, gas line antifreez will take the water out of the tank,and then run some 44k or MI3000.
 
Joined
Apr 22, 2004
Messages
1,502
Location
Johannesburg, South Africa
 
 
 
That top plate is all there is to a Weber. Pull that off and you can adjust the float and clean the jets and all that. A backfire can be a timing problem or ??? Hopefully someone with more experience will chime in on that. But your description of problems accelerating made me think of my float adjustments.
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
I added 5 gallons of 94 octane to it before I ran it. Though it did run before a few time with the old gas. I can add the tank additives - good idea. Would it cause this behavior?

AndrewT
 
Joined
Jan 26, 2005
Messages
4,874
Location
in the garage
(quote)Would it cause this behavior?

you mean water getting in the tank?
just condensation,gas just sitting doesnt do any good. :frown:
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Jason,

Got the top off. The float bowl is about 1/4 full or so. Does this seem right? Also, how do you adjust the float level?

AndrewT
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Hmmmmm - accelerator pump seems to be working as I get gas squirting when I move the linkage. However, I get gas squirting from both jets. Is this normal?


AndrewT
 

brian

SILVER Star
Joined
Feb 7, 2003
Messages
10,611
Location
lebanon,pa
 
 
 
if i read that right, you added the regulator during the time it was sitting?
this is based on that assumtion:
it's your regulator.
it's not flowing enough volume. under load or high rpm, you're draining the bowl of fuel and the reg is to blame.

i went threw this same thing. truck ran good for years with no regulator, read all kinds of posts about running a reg, so i added one. set it for 3psi or so, and the thing ran liek crap under load or at high rpm.

remove it and give it a try, my bet is your problem goes away.
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Regulator was bought today only and not yet installed so thats not the issue. Or the issue is I don't have a regulator though that makes no sense as this ran fine before w/out one.

AndrewT
 
Joined
Jan 26, 2005
Messages
4,874
Location
in the garage
throw some fuel additive/cleaner in it, cant hurt.
have you checked your fuel filter? change it, check the timing,plugs,
 
Joined
Feb 6, 2002
Messages
15,133
Location
OC, CA
 
 
 
 
NJFJ40 said:
Truck has been sitting alot for past 18 months or so during rebuild. Ran great before rebuild.
Sitting for a long time often ends up plugging the emulsion tubes and air bleed vents. If the spray cleaner and hand choking trick doesn't work, it is time to clean everything in carb dip, blow out all the holes and tiny passages and verify that they are clear and reassemble. Webers seem to need to be jetted for the 2F as they seem to run rich right out of the box. Get a hand full of different (smaller) main jets and take it to your local smog shop and start changing jets until the CO level in the tail pipe drops to the lowest level W/O the HC rising.
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
OK - some more info as I've been working on it tonight.

Dwell is at 36. Timing looks good. Compression is 150 across the board (never seen that before). Fuel pump pressure is right around 4psi. Dist cap is fine and points are good (didn't check point gap yet).

Also - took top part of carb off and cleaned what I couldf. Float chamber was 1/4 full or so. Float is moving freely as is the psiton its on. Took out the air jets and the e-tubes and they looked pristine. Cleaned them with wire and then carb cleaner and also blew cleaner thru them after and no debris or resistance. Accelerator pump jets spray good stream when throttle is moved. I basically removed, checked and cleaned all items I could with the top housing off. Guess I will take the main body off tomorrow and go for a dip.

Also removed plugs and they don't look so good but didn't think they could cause such issues. Will replace tomorrow.

I am thinking the only thing I haven't checked is valve clearance. Should I do this before dipping?

AndrewT
 
Joined
Apr 22, 2004
Messages
1,502
Location
Johannesburg, South Africa
 
 
 
NJFJ40 said:
Jason,

Got the top off. The float bowl is about 1/4 full or so. Does this seem right? Also, how do you adjust the float level?

AndrewT
Sounds about right, IIRC that is. There is a small tab on one end of the float, by bending that it adjusts the level of the float. I am away from my manuals or I could tell you exactly how to adjust it. I can never remember right off the top of my head because you hold it one way and measure.... then bend the tab accordingly. If I get back to the house I will let you know.
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Thx but I figured out the float adjustment. Its basically as you state above.

Appreciate the follow-up reply. Think I will be checking the valve clearances tomorrow.

AndrewT
 
Last edited:
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
Any idea why the weber 38 has two idle mixture screws on both sides of the carb? And do you need to adjust both?

AndrewT
 
Joined
Jan 26, 2005
Messages
4,874
Location
in the garage
NJFJ40 said:
Any idea why the weber 38 has two idle mixture screws on both sides of the carb? And do you need to adjust both?

AndrewT
yes, adjust both.
if i remember correctly, i dont think doing one before the other matters,but turn one in slowly untill you can hear or feel a difference in the way the engine runs.then back it out just a bit untill it smooths out.
then do the same for the other.
 
Joined
Oct 8, 2003
Messages
462
Location
Near Junk
OK - I am one happy puppy. Turned out the PCV valve was stuck. Took it off and air flowed both directions. Shaked it around and something freed up. Then air only flowed one direction as per spec. Hooked it up and suddenly smooth idle. Will replace with new one tomorrow.

I took it for a ride and got this horrible bucking. Felt like fuel starvation. I had put on the fuel reg earlier today just to see if that helped and had it set to 2.5psi as per weber spec (called them today). Changed setting to 4psi and no more bucking. Truck is running great and road test was awesome (first ride in a long time). Will probably just remove fuel reg altogether as its really not doing anything now.

Thx for all the posts w/help.

AndrewT
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom