Motorcraft 2150 problem

[AlexJordan22]

My carb was bogging and had a leak at the accelerator pump. I bought a rebuild kit from BJs and got it done. Before I rebuilt it it bigged under initial throttle and then ran fine with middle and full throttle.

I got it together and it starts and idles great, much better than it was and way smoother. It has a new problem now where it runs great at light throttle, but if I try and go 1/2 or 3/4 throttle then it has a huge flat spot where it just doesn't respond and sluggishly tries to catch up. It backfired out the exhaust here as well while driving. When it was apart I was pretty meticulous about cleaning everything with carb cleaner and my air compressor because I wanted to do a thorough job.

If I have the Jeep in Park or Neutral it will rev up without issue, but in gear and under load it really struggles which did not happen before. Adjusted idle mixture screws with my vacuum gauge and didn't touch anything except the carb. Timing was fine before the carb was removed and hasn't changed.

I'm looking into if this could be a power valve issue or something else. I do not have any fuel in the vacuum line going to the power valve. The kit came with a 2 stage power valve. I have 10-11" of vacuum at idle in gear. Any ideas help!

[Stuka]

I think you may have more than one issue. 10-11" of vacuum at idle is really low. It should be up closer to 18 in neutral.

So the first two things I would check is idle mixture, and timing. For a starting point on the idle mixture, set both screens to 2 turns out (turn them in till they just barely stop, and then turn them out 2 full turns). This is just a starting point. In my experience 2-2.5 is where they want to be in most cases.

It sounds like the accelerator pump may also be off and might need a bigger shot. Though this could be a side effect of an idle that is too lean.

Its worth verifying the timing also.

[tgreese]

You understand that vacuum holds the power valve closed, and usually you'll get too much fuel with a failed power valve. This sounds more like a too-lean condition to me, than too-rich. The stumble at mid throttle could be too little power enrichment from the power valve, or it could be a big vacuum leak somewhere. I would check around the base of the carburetor for a leak, or for something not connected leaving a big opening sucking air.

Did you have a two-stage power valve in there already? It would not be a terrible thing to put the old part back and see if there is a change. There's a chance the gaskets won't seal with repeated use, but generally the flat gaskets will be ok for a few cycles. A little grease on the flat paper gaskets might help. You could use some gasket cement, but then you won't be able to reuse the gaskets.

I would mention - the QuickFuel single stage power valves will work in these carburetors. Holley will not. NAPA sells the accelerator pump diaphragm by itself, and it seems to be a quality product. Much better than the Dorman pump gaskets, which might last a year or less.

[Stuka]

Oh, I forgot to mention the possibility of a vacuum leak which tgreese brings up. Use a flammable spray (brake clean or the like) and spray it around the base of the carb while the engine is running. If the idle goes up, you found your vacuum leak.

[AlexJordan22]

You understand that vacuum holds the power valve closed, and usually you'll get too much fuel with a failed power valve. This sounds more like a too-lean condition to me, than too-rich. The stumble at mid throttle could be too little power enrichment from the power valve, or it could be a big vacuum leak somewhere. I would check around the base of the carburetor for a leak, or for something not connected leaving a big opening sucking air.

Did you have a two-stage power valve in there already? It would not be a terrible thing to put the old part back and see if there is a change. There's a chance the gaskets won't seal with repeated use, but generally the flat gaskets will be ok for a few cycles. A little grease on the flat paper gaskets might help. You could use some gasket cement, but then you won't be able to reuse the gaskets.

I would mention - the QuickFuel single stage power valves will work in these carburetors. Holley will not. NAPA sells the accelerator pump diaphragm by itself, and it seems to be a quality product. Much better than the Dorman pump gaskets, which might last a year or less.

Yes, it had a 2 stage power valve in it before as well but it looked a little different than the one in the kit. I'll play with the mixtures a little too and see if that helps at all. It's a shame because it's finally idling and running so much better! I'd love to figure it out!

[candymancan]

Check your vacuum advance. Mine on my 76 J10 is bad. And i rebuult the carb. With the bad vacuum advance it will bog and wanna die on initial throttle from a stop. Kinda dangerous actually because if it dies when im making a turn i could be hit by traffic.

A bad vacuum advance can do this

[AlexJordan22]

Check your vacuum advance. Mine on my 76 J10 is bad. And i rebuult the carb. With the bad vacuum advance it will bog and wanna die on initial throttle from a stop. Kinda dangerous actually because if it dies when im making a turn i could be hit by traffic.

A bad vacuum advance can do this

Mine doesn't bog off idle anymore, but that was a reason I wanted to rebuild it. Now it sets off just fine *under light throttle*. But whether I'm just starting off or already cruising at 35 mph if I push the pedal about halfway down it just gives up and chokes a bit before sluggishly setting off. Never did that before I got the carb cleaned up.

[Srdayflyer]

is this the orig. carb?, everybody also over looks the butterfly shaft for wear and there is a lot , it goes mostly un noticed, but highly over looked, remember the throttle cable only pulls the butterflys open from1 side, the drivers side, i had mine rebuilt at a carb shop that only does carbs they found the shaft with step wear and the shaft bores oversized and were rebushed, how ever after i got it back and installed i didnt like the old tech,ran cold and a beast to warm up, just went with holy efi, game changer for me . just something to consider with the carb.

[AlexJordan22]

is this the orig. carb?, everybody also over looks the butterfly shaft for wear and there is a lot , it goes mostly un noticed, but highly over looked, remember the throttle cable only pulls the butterflys open from1 side, the drivers side, i had mine rebuilt at a carb shop that only does carbs they found the shaft with step wear and the shaft bores oversized and were rebushed, how ever after i got it back and installed i didnt like the old tech,ran cold and a beast to warm up, just went with holy efi, game changer for me . just something to consider with the carb.

Yes, original carb. I did not check for play in the butterfly shaft though. It operates smoothly so I didn't give it much thought. EFI would be nice, but this JEEP isn't worth that investment at this point to me unfortunately.

[tgreese]

IME a sloppy shaft will first affect idle speed stability. It is a vacuum leak, but pretty sure the idle speed will go up and down well before it could affect mid-throttle performance. It will come down to a different idle speed each time the throttle closes. You can move the shaft side to side and see if the idle speed changes. Or test with carb spray as Stuka mentions above.

If the shaft is sloppy, likely the least expensive cure will be an import replacement carburetor. You could have the carb body bushed at a bona fide carb shop, but I expect the repop carb would be cheaper.

[rocklaurence]

Yes, this team is correct. The Trickflow PVs work well the Holley's dont have enough threads to engage the 2150.. My J10 has approx' 14 " of vacuum at idle and the best PV that Ive found is the 8-9 " to minimize the bog or hesitation. They are cheap enough to by several and experiment with them until you find the best one.

[letank]

Yes, do the carb or brake cleaner spray around the carb base. I always change all the carb gaskets, especially the thick one, I use hylomar as a sealant, it allows you to reuse the gasket.

Recheck vacuum engine reading, at idle in neutral without the transmission load which lower the idle, your engine is a vacuum cleaner... the higher rpm, the higher vacuum.

[AlexJordan22]

Yes, do the carb or brake cleaner spray around the carb base. I always change all the carb gaskets, especially the thick one, I use hylomar as a sealant, it allows you to reuse the gasket.

Recheck vacuum engine reading, at idle in neutral without the transmission load which lower the idle, your engine is a vacuum cleaner... the higher rpm, the higher vacuum.

I did spray a bunch around the base and I did not have any leaks there. I was able to find a cracked plastic tee fitting with the carb cleaner spray though so I was able to fix that. Still have lots of old original vacuum lines I need to go through and replace as well.

[letank]

Recheck the PCV valve hoses between carb and firewall... that big hose gets a big soft... and the control hose to the charcoal canister... IIRC you could squeeze the control hose to reduce the bleed... t

Also things happen when the diaphragm in the charcoal canister bites the dust... the diaphragm start to have some holes... and yes there is a spring under that cover.

[AlexJordan22]

Recheck the PCV valve hoses between carb and firewall... that big hose gets a big soft... and the control hose to the charcoal canister... IIRC you could squeeze the control hose to reduce the bleed... t

Also things happen when the diaphragm in the charcoal canister bites the dust... the diaphragm start to have some holes... and yes there is a spring under that cover.

Is the charcoal canister in this vehicle the big yellow-y looking cylinder on the passenger side of the engine compartment with 2-4 rubber lines coming out of it? I know there is a large plastic canister attached in line of a rubber hose. Is that what you're referring to?

[tgreese]

I've never seen a yellow canister. All I've seen are black. All I've seen from this era had exactly four nipples on top.

Do you have the TSM? It will be pictured and described there.

FTVEC82Jeep.png

[letank]

Canisters loose their color sometimes, it can be a yellowish plastic tint

[backroadin']

I'm with Stuka - 10" of vacuum @ idle is really low unless you're really cammed up, which I don't think you are. FInd the vac leak/issue first before any tuning.
You can check for a lean condition pretty quick by bringing your hand down slowly over the carb at idle as if you were going to choke it off - if the idle improves when your hand gets close, or doesn't change when you completely cover the carb, then you have a lean condition. Also, check the color of your plugs.

[akguy09]

I would say the low vacuum could be attributed to elevation as well.....I live at 6500 FT above sea level, and I can get12-14" of vacuum at idle on a good day

[candymancan]

I've never seen a yellow canister. All I've seen are black. All I've seen from this era had exactly four nipples on top.

Do you have the TSM? It will be pictured and described there.


FTVEC82Jeep.png

Ive seen yellow ones. Its actually clear that turned yellow. I have one actually that i got off an 87 or 88 GW. And sold it on ebay.

Tbh i think charcoal canisters off topic fyi . Are a scam anyway. Charcoal only absorbs so much nefore ot become exhauated. It cant be renewed.. it has to be replaced.

I imagine after 3-6 months the charcoal is bad lol.. no diff than a fish tank or in house water filter to where it has to be replaced