Stuck Carburetor Jet


#1

It’s carb rebuild time for this diy’er. Ran into a bit of difficulty, a stubborn carb jet I can’t free up. Any helpful hints? Motocraft 2100 carb. One jet unscrewed ok, but with a good deal of effort required, the other seems determined to stay put. Concerned about miss-shaping screwdriver slot in brass jet if I apply too much force.

I’m thinking

  • penetrating fluid
  • heat – concerned about burning off eyebrows w/explosion
  • bigger screwdriver
  • impact screwdriver – the kind you whack with a hammer
  • seek professional help
  • forget about it, leave it installed, and clean the carb the best I can without removing it

Any ideas why Ford didn’t design their jets to accommodate hex sockets rather than screwdrivers?


#2

You might try locating a hollow ground screwdriver and see if that will work. It may take a little searching to locate a hollow ground one that size.
A gunsmith shop should have them.

If worse comes to worst you might try reaming the jet out with a straight pin and some aerosol carb cleaner. Hope that helps.


#3

In my rebuilds I have never even had to worry about main jet replacement, cleaning for sure, it might be necessary but would really need to know why you feel the main jets are an issue. If you are that far into it it might be better just to buy a rebuilt carb.


#4

There’s some definite signs of grit clogging the venturi tubes I removed for inspection, so I’m thinking I could clean the carb inner recesses more thoroughly by removing the jets first. The hole in the stubborn jet appears open enough though. And the symptom I’m trying to resolve isn’t consistent with a clogged jet so much as an idle circuit problem. So maybe you folks are right, just leaving that one jet alone is the best bet. I do have an overwhelming penchant for whacking it with the impact screwdriver … lol . .


#5

Do NOT use any kind of shock impact driver…you will shear the brass post haste.

I would simply use heat…shouldn’t be difficult. Many jets are two piece type with a hex outer edge and a screwdriver tip that im guessing yours is screwdriver only… same thing…Heat. See what you get…shouldn’t be dangerous if done properly… Its always worked for me…

Blackbird


#6

Use a screw driver that is a tight fit in the slot and as side as the slot while the carburetor is held firmly in a vice.


#7

You need the correct blade sized screwdriver for as close to perfect fit as possible. The screwdriver also needs to have a hex built into the shaft or at least a squared off handle. Place the body in a vise and position yourself so you can bear down on the screwdriver. Use a wrench on the hex (or adjustable on the handle) to provide the rotational force as you bear down on the screwdriver to keep it planted in the jet slot. It will break free with a loud pop…


#8

I would leave the jet in place, flush everywhere you can with the extension tube that comes with the aerosol can and hope for the best.
Idle and low speed passages tend to clog first.
I’ve fixed a few idle problems by doing no more than cleaning out the bowl and spraying in where the idle mixture screw goes.


#9

As @TwinTurbo predicted, the stubborn jet is out. And it came out with a loud pop. What worked, a bigger screwdriver, and heat. The bigger screwdriver was necessary, but not sufficient. I even gave the big screwdriver the old hollow ground treatment per @ok4450 's suggestion above, at least my amateur version. But even with that, the jet wouldn’t budge. But adding heat, that did the trick. Well, lack of heat, reverse heat. Cold is what I used. Being fearful of singed eyebrows, rather than a torch, I held an ice cube on that stubborn brass jet for 5 minutes, and then with the big screwdriver, it immediately popped, and was out in a jiffy.


#10

Congratulations! When I need heat I use an electric heat gun, at least there’s no flame. And, to clear a stuck jet, I use the smallest guitar string and poke it through.


#11

Yup…either way you slice it…Heat does the trick…or more accurately a Temp Differential…several ways to go about that. Glad you got it out.


#12

I prefer to remove carburetor jets and then soak all the parts in cleaner but spraying through the jet and confirming that the internal passages to the venturi are open would usually be OK. That 2100 carburetor is 40 years old and it might be worthwhile to leave no stones unturned though.


#13

I’ve done the soaking method before, but this time I’m just doing the spray-the-passages method. So far that’s my plan anyway. I found a couple of passages that were totally clogged and required a 30 awg wire to free up. This carb isn’t 40 years old. I replaced the original with this one, about 15 years ago.

A little education on the Motocraft 2100 carb theory of operation would be helpful, if anyone here can recall how it works.

  1. How is that booster venturi apparatus configured? There’s two small tubes on either side of a larger tube in the middle, the larger one is really a hollow bolt which also serves to hold the whole thing down. The two smaller tubes seem to communicate with the venturi ring ports; the hollow-bolt in the middle communicates with some small holes at the top of the apparatus. It was one of those middle ports was totally clogged. Is that part of the idle circuit? If so, that might explain part of the rough idling problem I’ve been having.

  2. I got a bit of a problem with the electric choke. The heating coil registers an open circuit. Is that more likely a broken wire in the heating coil, or is there a thermostat-contact somewhere in that electrical circuit? It seems like there should be an automatic off/on thermostat in the heater coil circuit, to prevent the coil from overheating, since it is powered up all the time the engine is running. Testing this theory, I tried putting some ice on the heating coil to cause this putative contact I’m imagining to close, but it continued to register an open circuit. Broken heater-coil wire or dirty thermostat contact? I don’t see any obvious way to inspect the heater coil area, it’s under a plastic cover held on by rivets.

  3. The choke heat function appears to be double-sourced. Besides the electrical heater, the choke spring housing is also heated by a sort of stove pipe arrangement, the heat source being an air pathway inside the shroud attached to the passenger side exhaust manifold. The circuit seems to be, cold and clean air is sourced from the top of the carb, then it goes via a tube to the exhaust manifold pathway for heat, then the heated air goes back up to the carb housing, then to the intake manifold via a small passageway in the carb which communicates to a port below the throttle plates. Doesn’t this represent an air leak direct into the intake manifold? Or is it small enough that it doesn’t cause a problem with the carb metering function?


#14

I’m not sure, but I’d think that electric heater would be always-on. It heats up slowly to open the choke after a while, right? If it shut down the choke would close. If I’m right, you have a broken wire somewhere.


#15

The electric assist on the choke is off below 80F. Once it reaches 80 an internal switch turns it on and it remains on. Of course the thermostat is not powered through the ignition system it is powered from the alternator stator which has no voltage unless the engine is running and the alternator is charging. When running normally the stator circuit should have 7v +/-.

The hollow bolt on the upper venturi is the feed for the accelerator pump. There is a ball check valve at the bottom of the hole and a weight inside the hollow bolt.


#16

That reminds me. Way back in the 70’s my mom had a 72 or something Sebring with the 318. It would go maybe 5 miles from a cold start and then stall on her. I OH the carb twice trying to resolve it. Finally my BIL looked at it and it had one of those electric choke devices. It was a little coin shaped deal. We simply removed it and never had a problem after that. Not saying to remove or ignore the dang thing but the car was only a couple years old and must have been a common failure point for Chrysler anyway.


#17

@“Rod Knox” writes

"The electric assist on the choke is off below 80F. Once it reaches 80 an internal switch turns it on and it remains on. "

Wow, that’s not something I would have never guessed. It seem totally counterintuitive. hmmm … Oh, well if that’s the way it works, that’s the way it works. It was definitely below 80 degrees when I tested it. Seems instead of ice for the resistance test I should have heated the electric choke up with a blow dryer. I did that for the thermostatic spring, and it was doing its thing correctly. OK, I’ll give that a go on the electric choke too, just to see if that circuit resistance decreases to a few ohms above 80 degrees.

Thanks again for the informative posts.


#18

@“Rod Knox” writes

I prefer to remove carburetor jets and then soak all the parts in cleaner but spraying through the jet and confirming that the internal passages to the venturi are open would usually be OK. That 2100 carburetor is 40 years old and it might be worthwhile to leave no stones unturned though

So far I’ve rebuilt this carb twice, and this is just in the past week … lol … It seems I may not know everything there is to know about this process. The first time the engine started and ran great for about 20 minutes, like new, then for no apparent reason the engine stalled and wouldn’t start at all unless I poured gasoline down the throat of the carb. So I took it all apart, re-sprayed the passages with carb cleaner, and again it started up and ran like new. This time for about 2 hours. I thought I had it licked finally so I parked the truck for the evening. The next morning it was hesitant to start. When it eventually started, it idled and performed very poorly. I could get it to go from very poor to just poor performance by turning everything in the “rich” direction. Doing this it was drivable, but barely.

So now I’m in the middle of the third rebuild in a week. This time I followed Rod Knox’s learned advice above and am using the “take it completely apart down to the practically the last screw and soak everything in Berryman’s carb cleaner for 20 minutes in a bucket” method. I’m done with the cleaning process but haven’t put it all back together yet.

One question I’m not sure about is the proper treatment for the throttle plate shaft. Since I soaked everything that shaft is now bone dry. I’m concerned I might be creating a wear problem between the throttle plate shaft and where it turns in the carb body every time I step on the gas. Should I lubricate that area with a drop of oil? Or is it designed to run dry, with no lube?


#19

I think it’s designed to run dry, but a drop of oil wouldn’t hurt. If it’s really worn it’ll be a vacuum leak source.