2150 carburetor issues

[Eric Kropp]

So I went to get my truck smogged and I can not get the idle to come down below 900 rpm. On one rebuilt by Guarantee Carburetor carb (I have many) I could get the numbers right but the throttle shaft is worn a lot and sucks a lot of air through the opening. On another one Rebuilt by National Carb it would do the numbers to and is not nearly as worn but still sits about 100-150 r's to high. I checked all the vaccuum lines and they are tight, I mean I could be missing something, but a first go-round showed the vaccuum lines to be good. It is possible that there is something wrong inside the National Carb that is causing this so I am rebuilding a core I picked up the other day and give that a shot. The Guarantee Carb has been in use for about 2 years, started getting a little bonky so I threw the National Carb on and figured all is good....til I got to the smog guy. Just for info...the National Carb has been in a shipping box for a couple of years, and had not been installed. I have sprayed brake cleaner in a number of problem areas and did not experience any increase in rpm. Should I do a vacuum leak down test....

Eric

 

[The_Dealer]

So I went to get my truck smogged and I can not get the idle to come down below 900 rpm. On one rebuilt by Guarantee Carburetor carb (I have many) I could get the numbers right but the throttle shaft is worn a lot and sucks a lot of air through the opening. On another one Rebuilt by National Carb it would do the numbers to and is not nearly as worn but still sits about 100-150 r's to high. I checked all the vaccuum lines and they are tight, I mean I could be missing something, but a first go-round showed the vaccuum lines to be good. It is possible that there is something wrong inside the National Carb that is causing this so I am rebuilding a core I picked up the other day and give that a shot. The Guarantee Carb has been in use for about 2 years, started getting a little bonky so I threw the National Carb on and figured all is good....til I got to the smog guy. Just for info...the National Carb has been in a shipping box for a couple of years, and had not been installed. I have sprayed brake cleaner in a number of problem areas and did not experience any increase in rpm. Should I do a vacuum leak down test....

Eric

get a vac guage and read the tech article, good info and can help u pinpoint it. i had that problem and i needed a stiffer return spring, and had a mani to carb gasket leak

 

[enginepaul]

Did you pull codes? The "idle motor" on the driver's side controls the idle speed by way of computer feedback and should compensate for a worn carb; unless it is real bad.

 

[kimcrwbr1]

I take it your running the computer. Just in case there are two idle adjustments, What would be the curb idle on the drivers side of the carb of a non feedback carb that holds the butterfly open. On the feedback system it is called the anti deisel adjustment just turn it all the way out so it is not touching the throttle lever on the base of the carb. The curb idle on the feedback system needs to be adjusted with the idle motor unplugged. When you turn the engine off the idle motor plunger fully extends unplug the idle motor and start it then adjust the idle motor to around 1500 rpm by loosening the bracket and moving the motor back to your desired high idle and lock it down. Then plug in the motor and the computer should take over the idle. If that works then you lower the anti diesel screw to where it almost touches the throttle lever that way when you let off the gas the throttle dont close too far before the idle motor take over. It is easier to adjust the carb with the air cleaner off but you must have the intake air sensor plugged in and all other sensors and vacuum lines. If you have run it with any of the sensors unplugged you will need to reset the computer first by disconnecting the battery for at least 15 minutes make sure everything is connected and run it for about 20 minutes for the computer to reset the values. I also found the best way to adjust the idle air screws is get the engine up to temp and at an idle unplug the idle control motor and turn the needles in or out for the highest vacuum or rpm. It is kind of a pain but it needs to be done in the proper order as adjusting the idle air will affect all the other settings here is the proper order.
1 turn your choke to stay in the open position when the engine is up to temp.
2 start the motor unplug the idle motor and back out on the antidiesel screw
3 adjust the idle air needles for the highest rpm or vacuum and make sure they are within half a turn between them.
4 plug the idle motor in while running and turn off the ignition the plunger shoud fully extend.
5 unplug the idle motor and set the curb idle by moving the motor back or fourth lock it down and plug the motor in, the computer should control the idle.
6 turn the antidiesel screw to where it almost touches the throttle lever.
7 Then you need to adjust the choke set the high idle cam on the v notch or manually close the choke to about 3/16 and push the throttle down a little so it sets on the cam start the motor and adjust the screw on the back lower of the choke to around 1400 rpm let it cool all the way down like the next day and adjust the choke thermostat to where it closes the choke all the way when you push the throttle half way then it is jus a matter of gettin the spring pressure right where it opens all the way after the engine is warm enough, make sure it opens all the way when the engine is around 130-140 degrees 4-5 minutes.

 

[dangerranger83]

Not to thread jack but still on the subject of 2150 carbs. when my dad and I go to start our trucks, we have to push hard in the gas pedal to "break it free" of something so that it works. Only does it when its cold outside. Anybody know what could be causing this? My dad unhooked the electric choke and went with a manual and it does this, mine is still electric at the moment (though not hooked up).

 

[Eric Kropp]

I did not pull codes. I don't have an OBD 1 reader. Yes I am running on the computer, or at least it isn't disconnected. The idle motor on my carb is not in play right now. It never even touches the throttle shaft lever and I don't know if it even has power. I also don't know anything about the idle motor, how it operates and what kind of problems are associated with it. I will need to read up on it. If it were in play it would probably make things worse. At this time the the butterfly's are completely closed and the idle is still up to high. So I need to find what else isn't right. The shop figured there was something in the carb wrong. I would like to think it is that simple, but when I was taking a core apart to rebuild, I have to say I don't see much that could cause that kind of problem, but we will see. Thanks for all the great info on the idle motor. I will keep you posted.

Eric<><

 

[enginepaul]

Eric: You can pull codes with a 12v. light or VOM - I think you need a manual at this point. Some mechanics just don't know these systems, including some dealer mechanics.

If the idle motor (driver's side of the carb) doesn't ever touch the throttle shaft, the engine isn't set properly. The computer controlled 2.8 runs as a system and it needs all components to function properly - although some here disagree. Meanwhile, a manual would help guide you in the right direction.
Please don't just start replacing parts as so many have done - it can be a waste of time and money; start with diagnosing the system.
I have lots of experience, including being a licensed mechanic at one time, and know how frustrating these can be; but once they run right, they run great. I'm on my second Ranger with over 100,000 mile total - both bought used and not running. (I junked one due to body damage, otherwise I'd probably still have it.)

Good luck

 

[kimcrwbr1]

The engine should not run with the butterfly all the way closed. how far out are you setting the idle air needles turn them out 1 1/2 turns from the lightly seated position. It sounds like you have the anti diesel screw down holding the butterfly open. Have you did the wet float adjustment. Pull the top off the carb the fuel should be around 0.810 of an inch below the top of the float bowl to the center of the fuel not on the edge. You can run the engine with the top off to get it right.

 

[Eric Kropp]

So guess what? I could put a bag over the carburetor and seal it and it would still idle, and I mean idle just fine. So I checked and I checked for vacuum leaks and man, nothing. Then I thought of something....I replaced the PCV with one from a 400 Midland engine to reduce crankcase pressure from blow by. I put a new 2.8 PCV on and cha-ching, idle came way down to a crawl. I bet that will change the readings for low RPM smog to since it won't be suck so much unburned vapors. If I can get this dude past to smog, then I think it is time to rebuild an engine and get the idle motor working right. I agree completely with enginepaul, ......it is best to have all the stuff working correctly so the engine will run the way the factory intended it to. If we Californians want to keep the old rides, it is the way it has to be

I'll be in touch
Eric