Autolite 2100 - How Does it Look?

If any of you have been following my rough idle thread you know I've had a bear of a time working out why my engine went from perfect to crap in a day.

This is the same issue I'm working to resolve, but figured a new thread was in order as specifically I took my autolite apart to try to diagnose/rule this out as the issue. About 5 days prior to my issue beginning I had rebuilt the autolite, so I've got it totally broken down right now so I can have some non-amateur eyes tell me if anything looks off.

Pics
#1 - the base underneath wreaks of gas and seemed wet. I have a gasket BOTH above and below the base on install and the rear port goes to the PCV (which works fine).

#2 - The boosters are slightly wet. no idea if this signifies anything.

#3 - float looks good to me, I think. horizontal and I'll us the ruler to double check again on install.

#4 - gas sitting at the bottom of the bowl, I assume this means the power valve isn't leaking. It sat on the bench with me like this for 20-30 mins during disassembly.

#5 - Black gunk in the bottom of the bowl in spots. Here's some on my finger.

#6 - One of the pins had fallen out of the boosters, but you can see if fine in the next photo. I lined it up prior to reassembly last time.

Pic #8 - Flappers fully closed.

Pic #9 - Flappers fully opened.

So, everything look as it should? Thanks everyone, I need some better eyes than mine.

Hi, the throttle plates should open more.
The rest looks ok
Did you keep the float level gauge and other diagrams and instructions with the carb rebuild kit?
Did you clean everything at least twice with carb cleaner and work in a very clean and lit area?
I would follow the instructions closely as you do it again. Good luck

I want to see both side of the old base gaskets and the gaskets under the spacer plate if you run one. Do you have an EGR valve? If those get stuck open the truck will run bad.

pipeline010 said:

#6 - One of the pins had fallen out of the boosters, but you can see if fine in the next photo. I lined it up prior to reassembly last time.

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I would imagine that disconnected/broken idle feed restrictor in the main well/emulsion tube is causing most of the problem. Get a new carburetor or find a new venturi cluster that fits your carburetor.

tirewater said:

I would imagine that disconnected/broken idle feed restrictor in the main well/emulsion tube is causing most of the problem. Get a new carburetor or find a new venturi cluster that fits your carburetor.

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Yea, hard to tell by pics but you have multiple issues with that carb. Emulsion tube is an issue.

Dirt is an issue

When you rebuilt it did everything come out? Jets, all rubber, all seals, needle and seat, check float for leaks

Was there a checkball under the venturi?

Did you dip it? Did you blow out all orifices and check air bleed on venturi.

If it was clean when you rebuilt it where did dirt come from. That will hang needle valve open and cause high fuel level/flooding at idle.

As was mentioned previously was gas coming out of boosters at idle? That's a sign of high fuel level and flooding.

Find a good used spare off 2100 off a running truck on the board or from Nick in delaware. If you want to make a trip to central jersey I can give you a hand rebuilding it. Just leave it all together. I'm away next week so you have time to find one.

In the interim I'm concerned about your possible 2 dead cylinders. Do the compression and leakdown tests to avoid continued issues once you have a solid car ready to go back on.



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thanks for following the thread Joe, was hoping you'd pop over.

Rusty I don't have an EGR valve but from your post I kept a close eye when I reattached the mounting plate and tightened up the carb. it was wet all along the seam on the passengers side. not weeping/dripping, just wet by appearance.

Joe/Tire - thanks to your posts, and my own obsessive thoughts, I'm no longer believing this truck has any issue with its' engine (more on that in a sec).

No idea where the dirt came from. I soaked the thing in carb cleaner (the bucket), sprayed out all the parts with Gumout and finished it off with canned air. I would have eaten off of it.

There was a checkball under the venturi. Everything was there as I expected it to be, the only weird part was that broken 'emulsion tube'? To be honest I didn't know the function of any of the parts, I followed the guide to the letter so couldn't assess, jut cleaned and swapped whatever was in the kit.

I lowered the float to spec which turned out to be a little below horizontal. Assembled and reattached and this is what happened:

note: didn't tune carb, just seated then 2.5 on each.

-zip came back to the engine on test drive.
-idle still kinda rough, but if a normal person was next to me at a light they would just assume it was a muscly engine, not something was wrong like 2 days ago.
-at coast there was no misfires (prior there was misfires and rumbles only when I was off throttle, throttle on it was perfect). After about 4-5 mins the coast misfire came back but very low.

So 2 reasons now I don't think the engine has a problem:
1. carb recycling made the first change I've seen from all my troubelshooting.
2.
Before I put the carb in I still had my old plugs on there (was checking them vs new ones as issue cause). So I swapped the plugs, but they have an extremely restrictive plug end. I was wrestling with the one in the 8 spot due to the new booster and finally got it to seat. then thought:
"was that one in?" moving my tools off the truck, I was like ya totally that was in. was about to drop hood and thought well let me check again...felt in, felt fine, lemme give it just another push.... *click*

Went back to the number 7 and sure enough that wasn't seated either. I've been pulling and twisting everything so much the last 5 days I don't think I was very careful seating the wires. Hypothesis: Thats why it appeared to offer no change when I pulled them on and off.

Conclusion: I'm an idiot.

Last but not least:

I'll poke around and see if I can source a local 2100/2150 and get this thing moving right again. And Joe I may take you up on your offer.

Thanks guys.

Tune the carb to the highest idle with a steady vacuum needle on a vacuum gauge. Keep readjusting the idle speed to get it down to the right idle speed with a steady needle. Get right and the needle will be rock steady.

Where you able to fix the broken venturi cluster? It will never idle correctly with it the way it was in the pictures.

haven't no. I'm trying to source a new one without replacing the entire autolite (which is turning out to be somewhat challenging).

I have a budget in mind for the trucks restomod plan and a new carb wasn't in it but fitech was. If I can source a cheap venturi unit I'll go that way, but I may be going whole hog on the fuel injection earlier than planned cause at least I wouldn't be wasting 200-400 bucks on something I'll be replacing within a year anyway.

thanks for the tip about the idle tho; it seems we've finally found the real issue. I guess I underestimated how important that internal tube was.

You could probably find a good used 2100/2150 without too much effort or money. The Chinese knockoff's are ~$115.

I think you'd save money and time in the long run by investing in a working carburetor now and verifying that your engine runs well *before* installing FI.

pipeline010 said:

haven't no. I'm trying to source a new one without replacing the entire autolite (which is turning out to be somewhat challenging).

I have a budget in mind for the trucks restomod plan and a new carb wasn't in it but fitech was. If I can source a cheap venturi unit I'll go that way, but I may be going whole hog on the fuel injection earlier than planned cause at least I wouldn't be wasting 200-400 bucks on something I'll be replacing within a year anyway.

thanks for the tip about the idle tho; it seems we've finally found the real issue. I guess I underestimated how important that internal tube was.

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ya I can't really find any 2100s anywhere that don't look like they:
a. actually ARE 2100s
b. have a manual choke
c. don't look like death ($50 carb soak, $20 carb cleaner, $20 kit- 3 hours and still may not work)
d. dont cost way too much ($150 for the death ones, $300+ for rebuilt)

I would love to verify the carb as the problem, but really can't find any way to source a cheap trustworthy replacement just for verification.

where are you located pipeline
I have a couple of 2100s
i could send you one to rebuild or use for parts
Chuck

Thanks for the offer Attac. Delconick was actually able to get me exactly the size venturi I need and, according to him, it's ready to be bolted in without any cleaning. I think my wife is getting real sick of me smelling like gas and carb cleaner.

I was absolutely dead set against spending another nickle on solving this until I did my compression test. Did it this afternoon with a rental tester and here are the results (dry only):

1-150 - 2-155 - 3-150 - 4-150

5-150 - 6-140 - 7-140 - 8-150

So great stuff there. I knew the engine ran well but kinda shocking to see such solid and high numbers.

A guy on reddit sent me an image with an absolutely amazing diagram on the internal operations of the autolite 2100/2150. Had I seen this 2 weeks ago I would have absolutely known the issue was the carb. The engine is perfect at speed and crap at low rpm, I had no idea how differently the carb operated between these two states.

https://imgur.com/a/siLJ7

That image is from Bubba's Gran Torino site:

http://grantorinosport.org/bubbaf250/carb/carb02b.html

pipeline010 said:

Thanks for the offer Attac. Delconick was actually able to get me exactly the size venturi I need and, according to him, it's ready to be bolted in without any cleaning. I think my wife is getting real sick of me smelling like gas and carb cleaner.

I was absolutely dead set against spending another nickle on solving this until I did my compression test. Did it this afternoon with a rental tester and here are the results (dry only):

1-150 - 2-155 - 3-150 - 4-150

5-150 - 6-140 - 7-140 - 8-150

So great stuff there. I knew the engine ran well but kinda shocking to see such solid and high numbers.

A guy on reddit sent me an image with an absolutely amazing diagram on the internal operations of the autolite 2100/2150. Had I seen this 2 weeks ago I would have absolutely known the issue was the carb. The engine is perfect at speed and crap at low rpm, I had no idea how differently the carb operated between these two states.

https://imgur.com/a/siLJ7

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