the previous owner had vacuum hoses everywhere some not connected to the right spot. i replaced all the vacuums on the right spot but now it will not turn on unless a little gas is added to the carb. the po owner told me he messed with the fuel air mixture screw can anyone tell me which screw it is and how to adjust it
fuel air mixture fj60 (1 Viewer)
- Thread starter Gabemo
- Start date
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The idle mixture screw is normally capped. It is located on the valve cover side of the carb.
If the PO drilled out the cap then you'll be able to access the screw while the carb is installed.
How to roughly set the idle mixture, using the Lean Drop method is described in the FSM.
If the PO drilled out the cap then you'll be able to access the screw while the carb is installed.
How to roughly set the idle mixture, using the Lean Drop method is described in the FSM.
gregnash
Anal Retentive Analyst
Time to get yourself the FSMs and start going through them... Look on here for information on the LEAN DROP method as well. If the area that @Output Shaft is talking about has not been broken into DO NOT.... I REPEAT DO NOT break that seal unless absolutely necessary. Do everything else you can to get the carb running right, include rebuilding before you touch that screw.
- Thread starter
- #4
sorry I'm a newbie to car mechanics do you mind sending pics or diagrams? @Output Shaft
You can download scans of the manuals at the link below.
For Sale: - 40, 50, 60, and 80 series FSM for a hell of a price.
If working on your car is all new to you, I agree with gregnash and don't go fiddling with the idle mixture screw.
Get a vacuum gauge and see what your vacuum is (or isn't) when idling.
Read the FSM
For Sale: - 40, 50, 60, and 80 series FSM for a hell of a price.
If working on your car is all new to you, I agree with gregnash and don't go fiddling with the idle mixture screw.
Get a vacuum gauge and see what your vacuum is (or isn't) when idling.
Read the FSM
If the mix screw has been de-capped, it'll look like this:
But I would go through the emissions FSM and verify that all the hoses are in the right spot. It's VERY easy to mess them up, even if you've been staring at them for 10 years.
There are threads here, if you search, that describe the process. It's also in the FSM, but the description there is somewhat confusing.
You'll need a vacuum gauge and accurate tach, at a minimum, as the change in engine response is kinda slow, when you fiddle with the mix.
Is fuel half-way in the sight glass?
Do you get a squirt of gas from the Accelerator pump?
See what I mean ?
Search for Lean Drop
But I would go through the emissions FSM and verify that all the hoses are in the right spot. It's VERY easy to mess them up, even if you've been staring at them for 10 years.
There are threads here, if you search, that describe the process. It's also in the FSM, but the description there is somewhat confusing.
You'll need a vacuum gauge and accurate tach, at a minimum, as the change in engine response is kinda slow, when you fiddle with the mix.
Is fuel half-way in the sight glass?
Do you get a squirt of gas from the Accelerator pump?
See what I mean ?
Search for Lean Drop
Last edited:
- Thread starter
- #8
thank you for the pictures it just what i was looking for @Spike Strip. I'm going to work on it later today and ill let you know
Now I' a little confused. See my post from yesterday "
Idle and ignition timing help" any thoughts would be appreciated.
Idle and ignition timing help" any thoughts would be appreciated.
micruz60
Unleaded Regular
Aha ha ha, clear as mud... h8 interpreting manuals.
Its like a game
confused. Get the timing right, first.
Then while the engine is running, micro adjust the MIXTURE screw, pausing to see which direction the rpms go, (slower or faster?) to the target rpm. 'Where it will rise no further' from the fsm is confusing. But you will figure it out. Over to idle SPEED screw, which brings the rpm back into 650 range, return to the mix screw, rising the rpm, back to speed screw, repeat until frustrated. until the max speed won't rise any...
700 rpm is fine.
One trick might be to have the choke pulled out, screwdriver into carb throat, set fast idle to near 1800 rpm (fast idle screw is different from the mix and speed screws), and then work toward the regular idle when the choke is pushed in? Then there is the throttle positioner. Study well the fsm.
Its like a game
confused. Get the timing right, first.Then while the engine is running, micro adjust the MIXTURE screw, pausing to see which direction the rpms go, (slower or faster?) to the target rpm. 'Where it will rise no further' from the fsm is confusing. But you will figure it out. Over to idle SPEED screw, which brings the rpm back into 650 range, return to the mix screw, rising the rpm, back to speed screw, repeat until frustrated. until the max speed won't rise any...
700 rpm is fine.
One trick might be to have the choke pulled out, screwdriver into carb throat, set fast idle to near 1800 rpm (fast idle screw is different from the mix and speed screws), and then work toward the regular idle when the choke is pushed in? Then there is the throttle positioner. Study well the fsm.
gregnash
Anal Retentive Analyst
One thing, or realization, that really helped me when I first started working on BeBe was this...
These trucks are ANALOG not digital.. Working on newer vehicles you will see instant response to even small changes (or close to immediate). For these trucks with their stock setups you have to give everything a minute or two to "adjust" to what you have done. Get a piece of tape and overlap it with a small flap around your screwdriver you will be using to make adjustments, making a small flag. This will be your indicator when you turn a set screw a specific amount... Use this to help with your adjustments along with having a small notebook and pen/pencil with you so you can take notes, write numbers, etc. as you go through your adjustments. This will help you keep track of everything.
These trucks are ANALOG not digital.. Working on newer vehicles you will see instant response to even small changes (or close to immediate). For these trucks with their stock setups you have to give everything a minute or two to "adjust" to what you have done. Get a piece of tape and overlap it with a small flap around your screwdriver you will be using to make adjustments, making a small flag. This will be your indicator when you turn a set screw a specific amount... Use this to help with your adjustments along with having a small notebook and pen/pencil with you so you can take notes, write numbers, etc. as you go through your adjustments. This will help you keep track of everything.
Cruiser Jimmy
Moderator
Ha! I didn't know hashtagging started in the 80's.
I use a similar approach. When I want to re-adjust the idle mixture/speed according to the lean drop, I start with the idle mixture screw about two full turns out from lightly seated. I may have to adjust the idle speed screw to get it to run on it's own. I then follow the lean drop procedure. As I make adjustments to the mixture screw, I turn it 1/4 turn at a time. I then pause wait for the response, then adjust again. Each time only going 1/4 turn. By using a set adjustment each time, I can easily back track to a previous setting to confirm which setting is better. It's pretty easy to use the screwdriver handle to judge each 1/4 turn. Increments of less than 1/4 turn probably are not very significant with this engine/technology.
If you keep notes on how many turns total you came out, you might be able to start with three or four turns from seated the "next time".
On average, how many turns out of the mixture screw is about right at sea level? 4? I’ve heard these trucks like to run rich but I also don’t want to plug up my carb.
