carb is sick at upper rpms

Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
Basic info. 83 fj60 no smog, weber 32/36DFEV (PO put on)
i have set the lean best idle according to man. specs.

Okay, Today i took my "brick" as my son calls it for a high speed test got up to 75. yeah me. problem was that when i started to climb the hill i just went down at 75, and the carb loaded as gravity and reality brought the "brick" back down to 60 the truck almost stalled between 2200 and 2800 rpm in 4th. once the rpms got back to around 2100 it was fine and climbed the hill albeit alittle slower.

why the rpm cut out under load. it accelerates fine in first and second and the stumble now reappears in third in the same rpm range, if you slow down or shift engine is smooth again.

any help is greatly appreciated.

Thanks
Dan
 

FJ40Jim

The Cruiser Whisperer
SILVER Star
Joined
Sep 26, 2003
Messages
11,171
Location
Lancaster, Ohio, USA
Website
www.tlcperformance.com
Sounds like fuel starvation into the carb. Make sure the fuel pump is up to snuff, fuel filter is clean, fuel line from tank is not restricted...

Could also be a restriction at inlet needle of carb. That is a small carb, good for a 1.5-2.0L engine, so it has a needle & seat sized for the expected fuel flow. If the carb is trying to pour fuel into a 4.2L engine, the needle & seat may not flow enough fuel into the bowl to keep the bowl level up.
 
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
Sounds like fuel starvation into the carb. Make sure the fuel pump is up to snuff, fuel filter is clean, fuel line from tank is not restricted...

Could also be a restriction at inlet needle of carb. That is a small carb, good for a 1.5-2.0L engine, so it has a needle & seat sized for the expected fuel flow. If the carb is trying to pour fuel into a 4.2L engine, the needle & seat may not flow enough fuel into the bowl to keep the bowl level up.

Jim,

thanks. fuel filter is new, fuel lines not crimped. not sure about the fuel pump??? probably worth replacing though. weber suggests the 38 for the 60 but i have read in the carb threads that the original is the best way to go.

do you think i need to replace it???

would it be better to go with a oem rebuilt and set up for desmog

any idea on cost w/o core since i have a webber now???

Thanks
Dan
 

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Visit site
what size jets do you have in there?

air correction is on top and main jets are on the bottom in side the float bowl

it could be starving if your float level is not correct.

also too large a jet it will suck down the gas too fast going up hill and starve itself

also what elevation do you live at?....webers are very suseptable to elevation differences

next question what color are the pulgs? have you checked them?

sometimes also the accelerator pump gets sticky...located on your valve cover side...if you snap the throdel you can see a lever push on the pump arm from the front of the carb...you can free it up and it will work good with some wd-40
 
Last edited:

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Visit site
accelerator pump should move right up against the arm...if the arm moves and the valve moves slowly back that could be an issue
weber03.jpg
 
Last edited:

rchalmers3

I speak Toyota
Joined
Jun 29, 2007
Messages
1,539
Location
Playas de Nosara, Nicoya Peninsula, Costa Rica
Visit site
Dan,

x2 on fuel starvation, especially if your set-up is not altered and the truck previously functioned in the type of driving where you have recently experienced the driveability.

New filters, especially cheap ones are not always flawless, and can cause problems. Did the driveability surface before or after the filter change?

Delivery can be verified by measuring pressure and volume at the carb. Before replacing expensive stuff, why not test and measure the fuel delivery?

Also, don't discount spark. While you describe a classic case of fuel starvation, there is a possible opportunity for weak spark to creep in under the diagnostic radar!

Rick
 
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
what size jets do you have in there?

air correction is on top and main jets are on the bottom in side the float bowl

it could be starving if your float level is not correct.

also too large a jet it will suck down the gas too fast going up hill and starve itself

also what elevation do you live at?....webers are very suseptable to elevation differences

next question what color are the pulgs? have you checked them?

sometimes also the power valve gets sticky...located on your valve cover side...if you snap the throdel you can see a lever push on the valve arm from the front of the carb...you can free it up and it will work good with some wd-40

plugs looks fine, did a tune up last month,

elevation 450feet

yesterday was 50 degrees

like i said best lean idle was set and it shows the idle jet is too small.

power valve moves freely

never looked at rejetting carbs. what does it entail and will i see the fuel delivery the truck needs as opposed to replacing with a properly sized set up?

found a 38 webber on mud thats for sale.

thanks for the input and wisdom!!!!
 
Last edited:
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
Dan,

x2 on fuel starvation, especially if your set-up is not altered and the truck previously functioned in the type of driving where you have recently experienced the driveability.

New filters, especially cheap ones are not always flawless, and can cause problems. Did the driveability surface before or after the filter change?

Delivery can be verified by measuring pressure and volume at the carb. Before replacing expensive stuff, why not test and measure the fuel delivery?

Also, don't discount spark. While you describe a classic case of fuel starvation, there is a possible opportunity for weak spark to creep in under the diagnostic radar!

Rick

Rick thanks

after a fuel filter change but it was two months ago.

how to measure volume and pressure at the carb???

when you say spark are you talking coil??

i guess what baffles me is that a spark or float or consumption issue would seem to surface consistantly.

i can accelerate hard in first and second through the power band ie 3200 rpm with no hiccup it just in third past 2100 and fourth past 2100 while under strain ie going up hill. first and second are fine on a flat and going up hill??????

doesnt make sense to me:bang::bang:
 
Last edited:

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Visit site
a 38dgas is a better sutted carb for the 2f

sound like your problem is a float level issue or crud in the float bowl or fuel pump issue or even the fuel filter located in the carb.


take a look at the inside of the float bowl...and clean it out...the top of the carb comes off with 6 screws and a c clip.

the fuel filter is the large brass nut underneath the cantelever section next to the fuel inlet
 
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
a 38dgas is a better sutted carb for the 2f

sound like your problem is a float level issue or crud in the float bowl or fuel pump issue or even the fuel filter located in the carb.


take a look at the inside of the float bowl...and clean it out...the top of the carb comes off with 6 screws and a c clip.

the fuel filter is the large brass nut underneath the cantelever section next to the fuel inlet

Thanks

i will try that and see.

do you know what the float level measurement is??? i guess i will need a new gasket/rebuild kit???

i will pick up a fuel pump and new filter tonight.
 

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Visit site
Thanks

i will try that and see.

do you know what the float level measurement is??? i guess i will need a new gasket/rebuild kit???

i will pick up a fuel pump and new filter tonight.


float measurenment is i believe 44.5 drop

you do not need a new gasket...as long as you dont break the old one...it is quite thin so be carefull...i have only bought one rebuild kit in the 100,000 miles my weber has been on the rig.

I have had the top plate on and off may times to do cleaning and rejetting from my old engine to new engine...if it is very brittle you can put alil white litheum grease on your fingers and lightly coat the gasket...it should seat just fine...use a star pattern when re-installing screws....like when you put lug nuts on

the fuel filter inside the carb is a reusable filter...just clean it out if its gunked up and inside the filter housing
 
Joined
Mar 18, 2008
Messages
3,897
Location
Washington, UT. The Promised Land
Visit site
Webers are fantastic carburators, my favorites of all that I have worked with over the years. (The list consists of Holleys, Rochesters, Cater/Edelbrock, stock Asian trash and Webers) You have a good carb but you're not getting enought fuel, I'd bet the farm on that. I reccomend removing the filter on the carb, they are small and clog easily. You have a filter in the line already. Check that, make sure your tank is venting properly, If there is a vaccuum when you remove the gas cap, get a new gas cap. Make sure that the fuel lines are conected correctly. The one that goes throught the filter is the one you want. There is a return line, make sure you are not feeding the carb through that one. Take off your fuel filter and try to blow air through it, or simply cut it open and see what you have. If it's full of crud, you may want to think about cleaning the tank out. Try compressed air through the fuel line from the filter towards the tank and see what type of resistance you get. This happened to a friend of mine; a previous owner had put on a Weber, fed it through the wrong line, left off the gas cap. Over time, water got in the tank and made some fair amounts of rust. Since the carb was feeding through the return line, it bypassed the filter. The stock fuel pump filled with rust and other junk from the tank and it ran badly to say the least. It would go about five miles before it would refuse to move any more. I think that you have at least one of the problems I mentioned, possibly more than one. In the end you wil love that little carb, it's a set it and forget it affair, although the one you have is a tad on the small side.
 
Joined
Mar 18, 2008
Messages
3,897
Location
Washington, UT. The Promised Land
Visit site
edit....you are correct my bad...you can stand down now :) :p

did a guick check....and i missused terminology....it is accelerator pump....but same infomation applies

The accelerator pump only compensates for a lean condition that would otherwise exist when the throttle opening increases suddenly. It does NOT meter fuel at a constant or slowly changing throttle position and cannot be suspect for a lean condition. Just my two cent's worth.
 
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
float measurenment is i believe 44.5 drop

you do not need a new gasket...as long as you dont break the old one...it is quite thin so be carefull...i have only bought one rebuild kit in the 100,000 miles my weber has been on the rig.

I have had the top plate on and off may times to do cleaning and rejetting from my old engine to new engine...if it is very brittle you can put alil white litheum grease on your fingers and lightly coat the gasket...it should seat just fine...use a star pattern when re-installing screws....like when you put lug nuts on

the fuel filter inside the carb is a reusable filter...just clean it out if its gunked up and inside the filter housing

sweet thanks

might night got screwed up so i will give it a go tomorrow evening. when i look at the jets for sizing are they number stamped ??

plans for tomorrow

new fuel pump
new fuel filter
clean internal filter in carb
clean bowl
adjust float to spec
check jet sizing

anything i have left out????

thanks again
dan
 

JohnnyC

Long ago TLCA# 2231
Joined
Jun 17, 2005
Messages
17,027
Location
UpState Ny, Wells Me
Visit site
The accelerator pump only compensates for a lean condition that would otherwise exist when the throttle opening increases suddenly. It does NOT meter fuel at a constant or slowly changing throttle position and cannot be suspect for a lean condition. Just my two cent's worth.

i agree ...like i said it "could be an issue" that he may want to correct...not that its a reason for his carb problems.

you need to look and take into account all problems and correct them at one time not piece meal...thats all :) ( my unconventional thinking :rolleyes:)

for what its worth i also agree with your 2c :) sooo...my 2c plus your 2c equals 4c :D

it is the cause of hesitation in alot of casses...but i wasnt going to get into the whole dynamics of how it works.

a guy i once worked for called it the thing that gives a "squirt" :)
 
Last edited:
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
float measurenment is i believe 44.5 drop

you do not need a new gasket...as long as you dont break the old one...it is quite thin so be carefull...i have only bought one rebuild kit in the 100,000 miles my weber has been on the rig.

I have had the top plate on and off may times to do cleaning and rejetting from my old engine to new engine...if it is very brittle you can put alil white litheum grease on your fingers and lightly coat the gasket...it should seat just fine...use a star pattern when re-installing screws....like when you put lug nuts on

the fuel filter inside the carb is a reusable filter...just clean it out if its gunked up and inside the filter housing

okay. took the top off bowl was clean, filter clean, float was set at 44 mm when top held at verticle measured from gasket to bottom of float with seat touching the ball. is this the 44mm in need or is it measured different???

i assume primary and secondary jets in orange in bowl numbered 145 on engine side, 150 on tire side. idle jets in red circle numbered 774 engine side and 775 tire side

also replaced fuel pump and fuel filter. havent started yet cause am iffy on what float measurement should be ie points of where it should be taken from at verticle and when horizontal what should it be at full drop i have 55mm now from gasket to bottom of float when held horizontally?????.

thanks
carb1.jpg
carb2.jpg
 

rchalmers3

I speak Toyota
Joined
Jun 29, 2007
Messages
1,539
Location
Playas de Nosara, Nicoya Peninsula, Costa Rica
Visit site
Dan,

Low pressure or low volume fuel delivery will give you the symptoms you are experiencing.

Did you take a few moments and confirm proper fuel delivery? You will want to make sure your carb is being delivered the fuel it needs to do it's job. Otherwise your investigative work on the carb will prove fruitless.

A FSM may serve you better than general info, but generally for a carburetored engine you can expect the fuel to be delivered at 3 to 7 PSI at a rate of a quart or liter every 15 seconds of engine cranking.

Forget my earlier mention of weak spark. I think that would manifest on accelleration immediately.

Sorry I didn't get back to you after my earlier post, best wishes with your finding a remedy.

Rick
 
Joined
Jan 26, 2008
Messages
582
Location
central virginia
Visit site
Dan,

Low pressure or low volume fuel delivery will give you the symptoms you are experiencing.

Did you take a few moments and confirm proper fuel delivery? You will want to make sure your carb is being delivered the fuel it needs to do it's job. Otherwise your investigative work on the carb will prove fruitless.

A FSM may serve you better than general info, but generally for a carburetored engine you can expect the fuel to be delivered at 3 to 7 PSI at a rate of a quart or liter every 15 seconds of engine cranking.

Forget my earlier mention of weak spark. I think that would manifest on accelleration immediately.

Sorry I didn't get back to you after my earlier post, best wishes with your finding a remedy.

Rick

Thanks rick,

fuel flow has been a main question. thats why replaced the fuel pump to make sure starting with a good pump and a clean filter. not sure how to measure the fp on a carb engine though. really would like to know the true float setting so that can be verified as well.

thanks dan
 

Users who are viewing this thread

Top Bottom