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How to Rebuild Your Motorcraft 2150/2100 Carburetor
Contributed By: Michael Baxter
This How To applies to the mechanical float bowl vent version of the 2150 and the later 2150 without a mechanical float bowl vent. I believe they are referred to as the 2150-2 and the 2150-3 respectively. The 2150-2 was used on 2 bbl. V-8 Full-Size Jeeps (FSJs) circa '77-'79 sold at high altitude while the 2150-3 was used on all V-8 FSJs from '80 and up.
The 2100 used on FSJs before circa '80 is mostly a different animal. It has the choke pull-off mounted in the air horn area and doesn't have an altitude compensation circuit. The information contained here except for the procedures on the choke and alt. compensation circuits most likely applies to the 2100 Carb. as well.
When I disassemble a carb. I do a few things to make the project easier. If I remove an "E" clip from a linkage arm, I reinstall it back in the groove after removing the linkage. Where ever I can, I put fasteners back in their original holes after removing a part. I also save all the old gaskets so I can compare the old ones to the new ones supplied in the carb. rebuild kit. Carb. rebuild kits often cover more than one model and the 2150 kit is no exception. It also has the appropriate gaskets to cover the 2100. They each utilize gaskets which are very close to each other in appearance. Especially the top cover/float bowl gasket.
The quality and completeness of carb. rebuild kits does vary. Prices vary from $25 to $45. I've had good luck with 2150 kits from Borg-Warner and Sorenson. Although, I recently had trouble with the neoprene/nitrile parts in a Borg-Warner kit for a Japanese carb. The many different brand names on carb. kit boxes make it hard for me to make any recommendations about a certain brand here. Once you obtain a kit and before you remove the cellophane, you can e-mail me with the brand-name. If I recognize the brand, I'll tell you what I remember.
Set-up is covered in the instructions which come with the rebuild kits and it is also covered in the Jeep Service Manual for your FSJ's model year. To date, the specs. listed on the sheet included with the rebuild kits has always been accurate enough. I do recommend you compare the sheet to the Service Manual nonetheless.
There are 9 or 10 adjustments which need to be made. The specs. included here are close enough to get you in the ball park. for any 78 & up 360.
There are several compression fittings in the fuel system. When unfastening compression fittings it is best to use a flare wrench(s). If you don't own a set of flare wrenches, I recommend you buy a set. I've never ruined a compression fitting when flare wrenches were handy but, I've ruined plenty when they weren't available.
I recommend you print this How To and then use it as a check list as you work.
First a tour of the 2150:
Looking from the front of the carburetor with the air cleaner housing removed. I'll divide the carb. connections & features into 3 areas. Top, middle and base.
The top area features a 90 degree port right above the float bowl and in front of the air horn. The air horn is the area within the 5 1/8" round surface where the air cleaner housing seals. The 90 degree has a rubber line which is ultimately connected to the purge canister. This is the float bowl vent. Also connected to the top cover is a rubber line located on the rear of the carb. and towards the passenger side. It provides filtered air to the choke stove in the intake manifold. The choke stove has two metal tubes which are a press fit into it's top plate. Finally, the choke valves (one big and one very small) are located in the top of the air horn.
For the middle area: On the driver's side front corner of the carb. is the anti-diesel solenoid which has a single wire connection. Next to it on the front is the square shaped accelerator pump diaphragm housing which is secured by 4 screws. Two of the screws also fasten the float bowl vent linkage to the carb. on the 2150-2. On the passenger side you'll find the choke assy. with a square metal plate blocking direct air flow across the linkage from the fan. The choke's bimetallic spring is housed inside the round housing. Behind the choke assy. on the passenger side rear corner of the carb. you'll find the choke pull-off diaphragm. Right next to the choke pull-off diaphragm, located in the center of the back of the carb., is the altitude compensation circuit. And finally the throttle linkage assy. on the driver's side of the carb.
For the base area: The idle mixture adjusting screws are located on either side of the front. They are each angled a little toward the outside. Facing forward right next to the driver's side idle mixture adjustment screw is the EGR port vacuum source. This port's tube is graciously extended on the 2150-3 to facilitate hooking-up the vac. line and adjusting the driver's side idle mixture screw. Directly under the float bowl is the power valve well. On the passenger side of the carb. towards the front is the ignition port vac. source. On the back of the carb., towards the passenger side, is the vac. source port for the choke pull-off diaphragm. Finally, on the rear of the carb. towards the driver's side is the large PCV valve connection port. The 2150-3 has a extra port on the bottom of the power valve well facing forward.
Tools (* = optional or luxury):
- Good selection of flat blade screwdrivers ranging from 1/8" to at
least 5/16" including one long shaft 5/32" for setting the idle air
REMOVAL & DISASSEMBLY:
Warning: The newer choke pull-off diaphragm's (plastic housing) vac. connection nipple is very easily broken-off while removing the carb. The plastic housing version can show-up on either carb. Disconnect the vac. hose from the plastic nipple and be careful to not break the nipple when removing or working with the carb.
* The throttle cable connects to the linkage via a ball & socket arrangement. To remove the cable; lean in from the driver's side fender, grab the end of the cable where it connects to the arm on the throttle linkage and pull it toward you sharply.
* There is a "S" shaped metal tube (with a disc shaped valve in middle) which connects the choke's bimetallic spring housing to the heat stove on the manifold. It's located on the passenger side rear corner of the carb. There is a brass adapter fitting between the tube and the carb. which has pipe thread on the carb. side and a compression fitting on the other. Using a 9/16" open-end wrench to hold the brass fitting stationary, use a 1/2" wrench (preferably a flare wrench) to unscrew the the compression fitting. Once the compression fitting is loose, leave it as is.
Disconnect everything else connected to the carb. including:
* air cleaner housing including the TCS vac. line which runs from the rear
bottom of the housing to a manifold vac. port on the intake manifold behind the
* Remove and drain the carb. Don't remove the plastic insulator/spacer from the intake manifold. There is a gasket between the plastic insulator and the intake manifold which will likely be ruined if removed. However, you do need to remove the thick asphalt gasket. This gasket is included in the rebuild kits. It should have a small tab on one side which you can use to pry it loose by holding the plastic insulator/spacer in position and lifting-up on the tab. Stuff two rags in the throttle bore openings.
The choke: There are two levels to the choke linkage. The upper level which pivots around the rear of the bimetallic housing shaft and the lower level which pivots around the passenger side end of the throttle valve shaft.
* Unscrew the 3 screws fastening the heated bimetallic spring, retaining bracket and gasket to the housing and remove them. The retaining bracket can only go back on one way. Don't sweat it for reassembly. Be careful and don't drop the bimetallic spring since bakelite is rather brittle.
* Remove the "E" clip from the choke pull-off diaphragm linkage on the outer end of the rod (leaving the other end hooked to the choke linkage on the carb.). Disconnect the linkage rod from the long slot in the vac. pull-off. Some linkage rods have two 90 degree bends w/o the E clip retainer. If this is the case, there is nothing to do for this step and you'll have to manipulate the diaphragm when you remove it later in order to disconnect the linkage. Note for reassy.: This linkage passes straight back between the two rearward mounting posts of the choke housing.
This is a good time to test the choke pull-off vac. diaphragm which must work in order for the choke to work properly. You can provide the vac. source with your lungs or you can use a vacuum pump. Either way you should be able to easily keep the actuator fully retracted. Some leak-down is okay but, I've seen some diaphrams which will hold vacuum. The newer choke pull-off has a plastic housing and port while the older style uses metal. The plastic nipples are easily broken off as pointed-out earlier. A fix is to seal-up the broken nipple with epoxy. Then drill a small hole and epoxy a new nipple on the other side of the round housing such that it is clear of any obstructions. The choke pull-off is available from good auto parts stores.
* Remove the "E" clip from the upper end of the comparatively fat in diameter upper choke linkage to lower choke linkage connecting rod. Disconnect the rod from the hole in the plastic arm. Notes for reassy.: This link rod is located vertically just behind the front mounting post for the bimetallic spring housing. Also note there is a short post on the back of the bimetallic housing right in-between the upper and lower linkages which forms a stop for the fast idle cam. The almost triangular shaped arm (smaller of the two) of the fast idle cam articulates on the front side of this post.
* Remove the "E" clip fastening the choke valve link rod (going up to the air horn) to the back-half of the "U" shaped upper linkage. You won't be able to remove the link rod immediately so, put the "E" clip some place safe temporarily.
* Unscrew the 3 screws which fasten the bimetallic housing to the three posts protruding from the carb. body and remove. For reassy.; note the small gasket between the lowest carb. mounting post and the bimetallic housing's leg.
* You may optionally disassemble the linkage in the bimetallic housing for cleaning. Mark the forked-arm's position on the shaft and remove the screw. Be careful not to loose the Teflon sleeve/seal when you remove the shaft from the housing. Note for reassy.: Remember to reinstall the Teflon sleeve/seal. Warning: Don't dunk the bimetallic spring housing in carb. cleaner unless you remove the shaft. The Teflon sleeve/seal will disappear completely if immersed in carb. cleaner.
* With a 1/4" nut driver, remove the two screws which fasten the choke pull-off diaphragm and bracket to the carb. body.
* 2150-2 only; undo the clip which retains the accl. pump linkage to the throttle shaft. This is on the driver's side throttle linkage. Note which one of the 4 holes the rod is installed in. The rod is normally installed in the #3 hole or the 3rd hole up from the bottom. Undo the clip by prying-up on the tab where it clips to the linkage rod.
Then Remove the rod by swinging it 90 or 270 degrees until the tab aligns with the slot. Note which of the two holes in the accl. pump actuator arm the rod is installed in. It was placed in the inside hole at the factory.
* Unscrew the 4 screws which fasten the accelerator pump housing to the carb. body. Remove the accelerator pump diaphragm. If the outer housing is stuck, tap the cover lightly from above with a small punch. Don't try to pry the cover off with a screwdriver. Note the accl. pump diaphragm's cone shaped spring is positioned with the large diameter end towards the carb. body on all models. Also in the case of the 2150-2, note the two slightly longer screws fasten the mechanical float bowl linkage to the cover and the lower end of the bowl vent linkage rod passes in-between the the actuator lever and the carb. body.
* 2150-3 only; swing the accl. pump diaphragm cover with linkage rod attached up over the top of the carb. When the slot and the tab on the throttle linkage end of the rod align, disconnect the rod. The 2150-3 has only three holes in the actuating arm off the throttle shaft. They are numbered 2-4. The rod is usually installed in the #3 hole. Also, the 2150-3 accl. pump actuating lever at the pump diaphragm housing only contains one linkage hole.
There are a couple of other accl. pump configurations but, I've never encountered one in a 2150 for an AMC application. If your happen to encounter one of them, the specific parts and an exploded diagram are included in the rebuild kits.
* Remove the orange neoprene/nitrile plug between the accl. pump diaphragm housing and the float bowl (actually the accl. pump check valve).
* Unscrew the 4 screws which fasten the power valve housing to the bottom of the carb. body under the float bowl and remove. Using a 1" open-end wrench or equivalent adjustable wrench, unscrew the power valve. Note the gasket between the power valve and the carb. body as well as the gasket between the cover & the body. Note for reassy.: Don't over-tighten the power valve.
* Remove the 2 idle mixture adjustment screws by 1st turning each one in gently until they seat while counting the number turns. Note the number of turns and then remove them.
* Unscrew the 6 screws which retain the carb's top and remove the top. Watch-out for the rectangular plastic seal around the choke linkage rod.
Check-out the float assy. Note how the float damper spring is orientated on the pivot rod. The long straight end is up against the fuel bowl wall and the short "L" shaped end is under the float side of the hanger bracket. There is a metal clip which is seated in a groove on the needle valve seat (brass fitting screwed into the fuel inlet passage).
* Pry the clip out of the groove and remove complete float assy. Note the needle valve hangs from a tang on the bowl side (opposite the float itself) of the float's hanger bracket. Also note for reassy.: The float level should be set using the dry method (see Set-up below) before reinstalling the cover.
* Unscrew the needle seat from the body. There is a gasket between the seat and the fuel inlet. There also may be a metal shield fastened between the gasket and the seat.
* On the back of the carb., unscrew the three screws which fasten the aneroid wafer housing to the valve housing part of the altitude compensation circuit and remove. Note: Be careful with the aneroid wafer and don't submerge it in carb. cleaner.
Save the gasket and compare it against the gasket supplied in your rebuild kit. If the original gasket is thicker than the new supplied gasket and it's in good shape, reuse the old gasket. The original gaskets are ~.050" thick while all the gaskets I've encountered from rebuild kits are ~.030" thick. It's critical this housing seals. The carb. won't perform well otherwise. If you suspect a slightly warped surface which identifiable by being able to jiggle the gasket, especially at the bottom, once the 3 screws are tight on reassy.; use RTV Silicone on reassy. Lightly coat the lip on the valve housing side of the gasket. The lip is contiguous except around the bosses for the three screws.
* Remove the 4 screws which fasten the remaining valve housing to the carb. body. Once off, pull the dome shaped spring cage off (press fit) and gently remove the valve from the valve guide. The valve guide seal will either come out around the valve stem or stay attached to the guide. In the latter case, use a needle nose pliers to gently work the two tabs on the seal until it is free. Warning: Be very careful with the valve guide seal because they do not come in the rebuild kits. If your's is torn, RTV silicone works well for doctoring them up. Clean the seal with spray carb. cleaner before applying the RTV. Let the RTV dry for 24 hours before reassy. Note for reassy.: To reinstall the valve guide seal, 1st install the seal around the valve guide inside the valve housing by gently using needle nose pliers to work the seal by the two tabs. Then push the valve stem through the seal and guide to seat the valve.
* Use a 5/16" or larger flat blade screwdriver to remove the 2 main jets from the bottom of the bowl. Note: Main jets only need to be snugged when reinstalled.
* Using the same screwdriver as above, unscrew the single large screw which fastens the booster venturi assy. Remove the booster venturi assy. and the gasket. Note the big triangular shaped seal just under the screw and seal under the booster venturi mount. Also note the metal mesh screen inside the accelerator pump bore if equipped.
* Remove the rod used to weight the check ball from the accl. pump well (located under the booster venturi assy.).
* Cup your hand over the accl. pump well and turn the carb. upside down and catch the check ball in your hand.
At this point the carb. is fully disassembled except for the throttle shaft. The 2150-2 has a plastic sleeve on the throttle shaft which prevents the body from being submerged in carb. cleaner for more than 15 mins. or so. The 2150-3 doesn't suffer from this problem.
I soak all the small parts in a 1 gallon (paint style) can of carb. cleaner equip'd with a basket. The larger parts I soak in a 5 gallon can of carb. cleaner by dropping them in the with a metal wire tied through a convenient hole in the casting for easy retrieval. I wear Nitrile gloves while working with carb. cleaner and I agitate the cans frequently. After removing the parts, I rinse them with fresh water and either let them air dry or I blow them dry with compressed air. From there I put them in my solvent tank for a solvent bath and I force solvent through all the passages. Then I blow-out all the passages with compressed air.
To remove the throttle shaft:
It is a rather risky to remove the throttle shaft. Don't attempt to do this if you are inept at dealing with broken fasteners. The screws which retain the butterflies are peened during production. The screw heads can break-off. I have had trouble twice in the past. Once I managed to remove the broken screw without drilling and the other time I had to drill & tap two holes. I would guess I now have about a 90%, or higher, success rate when using the following procedure:
* Soak the 4 screws which fasten the 2 butterfly valve plates to the throttle shaft with penetrating oil. Repeat the application of penetrating oil often and the longer you soak them the better...in excess of 24 hours won't hurt. Also prop the body with the screw heads facing straight down to facilitate gravity moving the oil down the threads.
* Making sure the exposed threads are wet with penetrating oil, use a 3/16" nut driver to carefully remove each screw. Then remove the butterfly valve plates. The markings on the plates from the screw heads and the shaft make their orientation obvious. Note for reassy.: The screws can be carefully reused with red Locktite. Be careful not to cross-thread.
I would normally consider taking the throttle shaft out of a carb. a one shot deal. Once it has been done and the screws Locktited, the chances of doing it again w/o having trouble diminish greatly. The screws must be locktited or you run the risk of a screw backing out and dropping in the engine ruining a piston and/or valves. If there is a lot of excess play in the throttle shaft to bore in the carb. body clearance, I would consider having the throttle bore drilled oversize and bushed. This can usually be done for $40-50.
* Using a suitable flat file and being careful not to gouge the bore or the venturis, file the rounded side of the throttle shaft around each of the 4 screw bores which fastened the butterfly valves until they are flush and smooth. If you don't do this, you will gouge the driver's side bore and/or center bore when you pull the shaft out.
* Mark the linkage arm on the choke side of the throttle shaft for position. Then remove the screw and the linkage arm.
* Gently slide the shaft out of the body. The shaft must slide out freely or more filing is necessary.
Reinstalling the rod which weights the accl. pump's check ball can be challenging. The trick is to tilt the body from side to side while you try to insert the large banjo screw into the bore.
* Follow the disassembly steps in reverse order above until you get to the point where the top cover is reinstalled. Before you reinstall the top, come back here.
* Set the float level (dry): Before the top cover is reinstalled on the body, the float level needs to be set. Measuring from the top of the float itself, 1/8" from the end or tip of the float, to the machined gasket surface on the float bowl (gasket removed) with the float in the up or shut-off position; the distance should be .555" (or 9/16"). A paper ruler is included in the rebuild kits to facilitate this measurement.
I find it easiest to hold the carb. body upside down, over the top of my head, to measure the distance.
- Mark the paper ruler with a pen.
If the distance is less than 9/16" (float level too high), the tang which the needle valve hangs from on the opposite side of the pivot from the float needs to be bent downward some. Vice versa for distances in excess of 9/16".
* Be sure to slip the rectangular plastic seal around the choke valve linkage rod before you install the carb.'s top.
* Return to following the disassembly steps in reverse order. Once the carb. is fully reassembled, return here and follow the steps below to set-up the choke and bowl vent:
* Choke valve pull-off set-up: This sets the initial choke valve opening for cold start. We'll use a drill bit to measure the distance between the lower choke valve edge and the air horn wall.
- Loosen the three screws and turn the bimetallic choke spring 90 degrees
rich (spring tighter)
* Fast Idle Cam Linkage: This adjustment is very similar to the one above.
- Open the throttle valves and then release them to ensure the fast idle cam
is set and the choke closed.
* Bimetallic spring setting:
- Turn the bimetallic spring back from the 90 degree rich position And set it in the area of 2-4 notches lean (less spring tension). I find the 2150s require a twice yearly adjustment of the choke spring. Once in the Spring to a slightly richer position for warm weather cold starts and then back (leaner) again in the Fall for cold weather starts. I leave the three screws just loose enough that I can turn the spring by hand.
* Choke Unloader: This adjustment bends a tang if necessary to open the choke valve properly for full-throttle cold engine operation.
- Hold the throttle valves in the wide open position.
* Mechanical float bowl vent (2150-2 only):
- Pull the choke valves full open and hold them there.
* Reinstall the carb. back on the intake manifold using the new asphalt gasket. Be sure to situate the S shaped tube between the choke housing and the choke stove before you fully seat the carb.
Don't over tighten the carb. bolts which can crack the carb. housing. Just snug them and recheck after a few weeks.
* Idle speed & mixture adjustment: It is crucial there are no engine vacuum leaks in order to adjust the idle mixture and idle speed and obtain a smooth idle. Vacuum leaks can be diagnosed using spray carb. cleaner. Ensure the vapor can't enter the carb. normally and spray around any engine vac. connections. You may have to plug some vacuum lines which run through the fire wall in your process of elimination (as you shouldn't spray carb. cleaner inside the FSJ). Don't forget any vacuum connections around the transfer case and front axle as necessary.
- Warm the engine to normal operating temp.
This is another adjustment which might need to be made seasonably. In the Summer when the hot air is less dense and the accessory load (A/C) higher, you may want to adjust the idle up a little. Vice versa for Winter.
* Fast idle speed adjustment:
- Open the throttle valves at the carb. and hold them open.
* Miller Time! Substitute your favorite libation for "Miller" as required. :-)
Corrections and comments gladly accepted.
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