- Thread starter
- #21
@Weber Sarge - back to shop now. Stock filter, OEM replacement due in tomorrow. Will check fuel inlet next. Rechecking vacuum now
Hesitation when accelerating, Carb, Coil or Ignition - Finally Fixed (1 Viewer)
- Thread starter ErikinSC
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
- Thread starter
- #22
Idling with 21" Using line to brake booster.
- Thread starter
- #23
And carb screen is clean, but partially collapsed on the sides
- Thread starter
- #24
And screen is clear.
thebigredrocker
SILVER Star
I am on the hunt for a vented gas cap because my three vent lines on the fuel tank were caped of by the PO and he must have sold the fuel separator that vents fumes in the engine bay. So I was surprised you found a vented cap from SOR. SOR's website is lacking specific details so I just called them and was told the cap they sell for 9/71 - 9/77 FJ40's is not vented. Just thinking if you don't end up finding an issue at the Carb, perhaps running without the gas cap would rule out the vapor locked fuel tank possibility. Obviously if the PO installed the proper size vent hoses and no blockage exists then you don't need a vented gas cap. Hope you find the issue. Let us know what you come up with.
- Thread starter
- #26
This is the fuel cap I ordered from SOR :
I'have the VSV in the engine compartment hooked to one of the fuel lines, but I'll have to chase them and do a pressurized air test to purge them. I'll run the truck this afternoon - and as soon as the problem occurs - I'll jump out and pop the cap to see if it is under vacuum.
I'have the VSV in the engine compartment hooked to one of the fuel lines, but I'll have to chase them and do a pressurized air test to purge them. I'll run the truck this afternoon - and as soon as the problem occurs - I'll jump out and pop the cap to see if it is under vacuum.
Last edited:
Someone that knows more than me, is that a "carb cooling fan" motor? Should it be?
Also, you said "on and off problem"...did the Cruiser have a bit of sitting up before this happened? The fuel pickup in the tank was getting clogged on mine. Long history of sitting before I got her. After a while it would fuel starve. Vacuum-locked against the fuel pick-up. Actress just like bad fuel pump, sticky needle, etc. A little air backward through the line was how I finally diagnosed it.
Also, you said "on and off problem"...did the Cruiser have a bit of sitting up before this happened? The fuel pickup in the tank was getting clogged on mine. Long history of sitting before I got her. After a while it would fuel starve. Vacuum-locked against the fuel pick-up. Actress just like bad fuel pump, sticky needle, etc. A little air backward through the line was how I finally diagnosed it.
Don't sweat the fuel screen being partially collapsed , it's just how they seat and no big deal . Just a quick idea - pull the distributor cap off and verify the timing advance parts aren't sticking , see if it will rotate against it's springs and return cleanly - if it sticks it would cause a lot of issues that mimic the carb .
Is the return line still in the engine bay near the charcoal canister ? There is a way to add a Jeep CJ filter to allow the use of a return line for the Weber . You haven't mentioned it - but is there any sort of pressure regulator in the fuel line to the carb ?
Sarge
Is the return line still in the engine bay near the charcoal canister ? There is a way to add a Jeep CJ filter to allow the use of a return line for the Weber . You haven't mentioned it - but is there any sort of pressure regulator in the fuel line to the carb ?
Sarge
- Thread starter
- #29
@robbs6940 - I recently learned that the carb cooling feature is for when the motor is turned off - it does not 'cool the carb' while the motor is running. * And I just got a carb cooling from from @woytovich. 
That install will happen later this spring. Truck has not been sitting - I've been driving it almost daily (except during late Dec / early Jan for upgrades) since I got it last fall.
@Weber Sarge - I will check, photo, post and verify the dist cap parts tomorrow. The return line is still in the engine bay... Im going to put the -40 back up on the rack tomorrow and I will be able to follow the route. I drove the truck last night down the interstate to a meeting, and did not have any hesitation issues to speak of. I picked up another OEM fuel filter, and will swap it out tomorrow also - but as clean as the carb screen was - I dubt that isgoing to be an issue.
Any suggesiotn as to checking the accelerator pump? Could the A.P. be an intemittent problem? or would it be a constant fault?
That install will happen later this spring. Truck has not been sitting - I've been driving it almost daily (except during late Dec / early Jan for upgrades) since I got it last fall.@Weber Sarge - I will check, photo, post and verify the dist cap parts tomorrow. The return line is still in the engine bay... Im going to put the -40 back up on the rack tomorrow and I will be able to follow the route. I drove the truck last night down the interstate to a meeting, and did not have any hesitation issues to speak of. I picked up another OEM fuel filter, and will swap it out tomorrow also - but as clean as the carb screen was - I dubt that isgoing to be an issue.
Any suggesiotn as to checking the accelerator pump? Could the A.P. be an intemittent problem? or would it be a constant fault?
Intermittent issues such as you describe at that throttle plate position indicates , as Pin Head so correctly pointed out - idle jet issues with fuel flow . Here's the thing about Webers that folks don't understand and more insight to what Pin Head is talking about -
You can dial in almost every bit of the fuel/air curve in any Weber carb . This is accomplished through idle jets , main jets and air jets as well as the emulsion tubes . Mains/airs take care of the available fuel to those circuits . The emulsion tubes determine how that available air/fuel is delivered . Your 38DGAS probably has F55 tubes which is an all-around and pretty evenly distributed fuel curve that easily follows main air fuel jet sizing . There are a ton of different profile emulsion tubes , an F6 - for example , will deliver a fairly even air/fuel rate at mid and higher flows but be very aggressive at low end of the mains . Same goes with the idle jets - these judge the amount of fuel/air mix available for the transition circuit holes just above the throttle plates . These are the transition circuits and progress in size and placement as the air changes position and flow speed as the throttle plates are opened . Designs vary - Holley and Carter-based designs (licensed by Weber) use a slotted transition instead of holes .
To dial a Weber into an engine , and they all must be dialed in , you set the lean best idle per instructions as well as base idle speed at fully warmed engine temps . As the engine is loaded , if it stumbles just off-idle (right when you step on the gas) this means the transition circuit is leaning out too far . Either the carb needs a larger idle jet size or the circuit has dirt in it . In your case , since this is an intermittent problem - yours has dirt in the circuit . The holes above the throttle plate as well as the idle jets are quite small - so any dirt goes there first and plugs things up . Yours is still driveable since it runs on both barrels all the time , unlike a progressive 32/36DGV series . So , that tells me one side has dirt still , possibly in the jets but more likely in the circuit itself . It can build up over time and the only way to clean it properly is to remove the carb .
Once off , remove the idle jets and the top cover , carefully . There is a small 1/8" c-clip that holds the choke linkage arm to the choke plate - watch that thing as it usually hits you in the eye before disappearing into oblivion ...
With the top cover off and idle jets removed , open the throttle all the way while upside down . With a bright light you will see a set of holes just above the point where the throttle plate sits at idle position . Spray those hole hard with brake cleaner using the straw and finish by cleaning out the float bowl as well . You don't have to remove the main jets in the bowl or the air jets on the top of the main body but it can help to clear debris . Finish with compressed air - the more the better . If you screw anything up , I have some parts left here and with pics can fix it from here as well .
One note - NEVER , EVER ADJUST THE SCREW ON THE GEARS ON THE THROTTLE LINKAGE OF A 38DGAS - THEY HAVE TO BE TIMED VERY CORRECTLY !!!
I've had to reset so many of them I'm sick of it , it takes a dual dial indicator to get them right or that carb will not respond off-idle as it should . A 38DGAS should be really crisp and quickly respond to throttle input if it's right .
Ok , fingers hurt ...
Sarge
You can dial in almost every bit of the fuel/air curve in any Weber carb . This is accomplished through idle jets , main jets and air jets as well as the emulsion tubes . Mains/airs take care of the available fuel to those circuits . The emulsion tubes determine how that available air/fuel is delivered . Your 38DGAS probably has F55 tubes which is an all-around and pretty evenly distributed fuel curve that easily follows main air fuel jet sizing . There are a ton of different profile emulsion tubes , an F6 - for example , will deliver a fairly even air/fuel rate at mid and higher flows but be very aggressive at low end of the mains . Same goes with the idle jets - these judge the amount of fuel/air mix available for the transition circuit holes just above the throttle plates . These are the transition circuits and progress in size and placement as the air changes position and flow speed as the throttle plates are opened . Designs vary - Holley and Carter-based designs (licensed by Weber) use a slotted transition instead of holes .
To dial a Weber into an engine , and they all must be dialed in , you set the lean best idle per instructions as well as base idle speed at fully warmed engine temps . As the engine is loaded , if it stumbles just off-idle (right when you step on the gas) this means the transition circuit is leaning out too far . Either the carb needs a larger idle jet size or the circuit has dirt in it . In your case , since this is an intermittent problem - yours has dirt in the circuit . The holes above the throttle plate as well as the idle jets are quite small - so any dirt goes there first and plugs things up . Yours is still driveable since it runs on both barrels all the time , unlike a progressive 32/36DGV series . So , that tells me one side has dirt still , possibly in the jets but more likely in the circuit itself . It can build up over time and the only way to clean it properly is to remove the carb .
Once off , remove the idle jets and the top cover , carefully . There is a small 1/8" c-clip that holds the choke linkage arm to the choke plate - watch that thing as it usually hits you in the eye before disappearing into oblivion ...
With the top cover off and idle jets removed , open the throttle all the way while upside down . With a bright light you will see a set of holes just above the point where the throttle plate sits at idle position . Spray those hole hard with brake cleaner using the straw and finish by cleaning out the float bowl as well . You don't have to remove the main jets in the bowl or the air jets on the top of the main body but it can help to clear debris . Finish with compressed air - the more the better . If you screw anything up , I have some parts left here and with pics can fix it from here as well .
One note - NEVER , EVER ADJUST THE SCREW ON THE GEARS ON THE THROTTLE LINKAGE OF A 38DGAS - THEY HAVE TO BE TIMED VERY CORRECTLY !!!
I've had to reset so many of them I'm sick of it , it takes a dual dial indicator to get them right or that carb will not respond off-idle as it should . A 38DGAS should be really crisp and quickly respond to throttle input if it's right .
Ok , fingers hurt ...
Sarge
- Thread starter
- #32
Busy week at work. Gonna turn a wrench later today, finally.
I'm going to put one of these onto my rig as well - in place of the OEM filter to see if it helps. Wondering if I might have to cap one of the fuel tank inlets? I have a TPI poly tank, and it appears the PO looped a vent and return into one another... effectively preventing the vent function from working. Ill route this into the stock return 'hard line' and see if it helps or not.
* @Weber Sarge - if this is a bad idea for my hesitation issue, let me know.
The filter must be installed after the fuel pump , never on the suction side . Closer to the carb is best .
Sarge
Sarge
- Thread starter
- #34
Tank - OEM filter - pump Vented filter - carb.
Where to route vent to? Back to atmosphere?
Where to route vent to? Back to atmosphere?
Vent routes back through the separator and charcoal canister . Depends on year and smog equipment .
Sarge
Sarge
thebigredrocker
SILVER Star
If all else fails and you start running out of daylight, take that girl for a spin with her gas cap off. If you have a full tank, siphon some out if that's a concern. Man, I'm rooting for Ya!
red
red
- Thread starter
- #37
LOL, she is under cover at my shop for the night. It's all fine.
My fuel cap is not vented; I did a blow tested & verified that. I have another cap I need to check on my other work bench. Currently hosed with a CCOT poly tank as show - but NOTHING is connected to the return line at this time. I was planning to 'vent' the CJ filter back to the tank.... Or tee into the charcoal canister system under the hood?
My truck has been mostly desmogged.
My fuel cap is not vented; I did a blow tested & verified that. I have another cap I need to check on my other work bench. Currently hosed with a CCOT poly tank as show - but NOTHING is connected to the return line at this time. I was planning to 'vent' the CJ filter back to the tank.... Or tee into the charcoal canister system under the hood?
My truck has been mostly desmogged.
Last edited:
- Thread starter
- #38
@Weber Sarge - if I tee in, would it make a difference to 'reverse vent' from the CJ filter into the output side of the charcoal canister where it currently is connected to the VSV? There is nothing else connected to the VSV. Or would I need to be on the input side of the canister?
vacuum leak-- prob in the manifold---
The bypass in the filter has to go directly to the return port on tank , nowhere else .
Sarge
Sarge
