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Unread 08-30-2009, 07:25 PM   #1
houstonmat
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304 v8 stock carburetor question/advice

I have a 76 CJ 7 with the 304 v8 and the stock 2bbl (motorcraft I think?). The carb has been rebuilt in the last 7-8 years, and even has a "Holley remanufactured" sticker on it.

She fires up just fine and once warm runs great. The problem I have is that when I push the pedal hard, it kind of chokes for a second and the whole thing smells like gas. I am not against replacing the carb, but I really want to keep it pretty darn close to original. Does that sound like a simple carb adjustment, or should I just go ahead and replace it? By the way, I can fix a lot of things, but I am an absolute carburetor virgin. I don't mind learning, and I did a lot of reading around the forum for info on float level and such. I am really just in need of some direction on what I should learn to fix first...or where I can get a replacement that's not going to cost a ton of money...

Thanks much!

Matt

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Unread 08-30-2009, 09:41 PM   #2
bigredisb
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I have this same issue with my 79 304 and I have tried tons of choke adjustments, accelerator pump adjustments, mixture adjustments, and timing checks but I cannot figure mine out either. The only symptom mine has differently is that it starts great when ice cold but if its warm at all I have a little longer cranking times to get it to fire.
I would also really like to hear what others have to say.

Plus I just rebuilt the carb because it was doing this so it also has all new parts and still does not run great.
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Unread 08-30-2009, 10:15 PM   #3
h2ojeep
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Right off had, I would start with looking at the accelerator pump. Also could be a power valve problem. Have you changed your fuel filter? At 7-8 years on a OH, i would go ahead with a rebuild kit.

if it is a motorcraft 2100/2150, they are easy to Rebuild for a novice. I like the 2100/2150 carbs and my runs cherry. good off road, needs a little adjustment for altitude, and gets OK mileage for a 304 jeep plus you get to stay original.

As to heat problems, make sure you reinstall the "heat gasket" below the carb. You can usually reuse the original, but it is important on the 304 to insulate the carb from the motor.

upon reinstalling or new fuel filter, make sure the return line is higher than the supply line, no exception.
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Unread 08-30-2009, 10:16 PM   #4
JeepHammer
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Quote:
Originally Posted by houstonmat View Post
She fires up just fine and once warm runs great.

The problem I have is that when I push the pedal hard, it kind of chokes for a second and the whole thing smells like gas.
Classic sings of a mis-adjusted accelerator pump not giving enough pump 'Shot' of fuel when you take off.

Accelerator pump is located in the front of the float bowl, and has a rod from the throttle blade linkage to the pump arm.

Try moving the linkage rod in the adjustment holes a little and see if that helps/hurts things...

Could also be the accelerator pump has seen better days, and needs some new parts.
Last time I rebuilt a MC 2100 carb, it was under $20 for the kit,
And they are a SNAP to rebuild!
Get yourself several cans of carb/choke cleaner,
Some cans of Brake parts cleaner (evaporates cleaner than charb/choke cleaner),
A $20 rebuild kit, and a flat, clean work surface.

I'd also get myself a couple or three magnets, good for holding small parts from running off!

Locate a digital camera, and take LOTS of pictures of the linkage so you will know where it all goes back to,
And watch for things like check balls, ect. when you disassemble.

Expect to take about 3 hours for first time disassembly, cleaning, reinstall and tuning when finished.

This really is a SIMPLE carb to work with, and excellent choice for first time carb re-builder...
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Unread 08-31-2009, 01:23 AM   #5
OldSkull
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Quote:
Originally Posted by JeepHammer View Post
Classic sings of a mis-adjusted accelerator pump not giving enough pump 'Shot' of fuel when you take off.

Accelerator pump is located in the front of the float bowl, and has a rod from the throttle blade linkage to the pump arm.

Try moving the linkage rod in the adjustment holes a little and see if that helps/hurts things...

Could also be the accelerator pump has seen better days, and needs some new parts...............


It seems to be a common problem after reading a few posts lately. I would really like to here what you find and what you do to fix it. I have the same problem. Jeephammer has given me some suggestions, but I did not get all of them done yet. My next step is to look at the accelerator pump and then if the diaphragm is not torn, I will make some trial and error adjustments of the linkage. Then I will go to the power valve

I'm curiuos if it is possible to get too much of a shot from the accelerator pump since mine is getting the max based on my current adjustment. I have a newly rebuilt carb and it is set like the old one was.
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Unread 08-31-2009, 10:18 AM   #6
JeepHammer
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What you may need to do is play with adjustments a little to see if you can find an 'Optimum' setting for your vehicle.
Don't be afraid to move the linkage around in the adjustment holes, it will either make things better or worse, but it's VERY easy to change to something different to try another 'Test'...
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Unread 08-31-2009, 11:19 AM   #7
zillla
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Are you sure you ave a stock carb on there?? The stocker is an MotoCraft 2100... The Holley sticker shouldn't be in there.. FWIW, I took a Holley off my 75 304 and put a 2100 back on.. I'd give the Holley away but nobody wants it..

Last edited by zillla; 08-31-2009 at 05:56 PM..
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Unread 08-31-2009, 02:36 PM   #8
bigredisb
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Interesting comments. I also thought the combination of accelerator pump / power valve so I rebuilt my whole carb and the problem stayed the same. I started with my accelerator linkage in the inside hole on the lever nearest the pump and I put the linkage 2nd hole down on the throttle shaft. I was getting thick black smoke upon sudden accel so I have it dropped to the 3rd hole down, mixture screws out about 1.5 turns and still get black under snap accel. If the engine has not been running for at least 15 min a snap accel will kill it stone dead with black smoke. I believe my carb has 44 size jets in it as well and it runs like its way too rich (which I think these are commonly reffered to as too small).
I am not trying to hijack the thread but thought I would throw out some info on what hasnt worked for me so far and I have heard this same situation about the 2100 several times.

The return hose thing is a good thing to check because my 2100 seems like fuel has evaporated out of it after it sits for a day or so because you can pull the supply line and not get a drop of fuel.
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Unread 08-31-2009, 04:02 PM   #9
JeepHammer
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You are supposed to get 'Black Smoke' when you accelerate.
Shouldn't get 'Black Smoke' at idle or when you are cruising.

The idea of the pump/power valves is to give a richened fuel supply when you accelerate or the engine gets a high load, like when you go up hills or pull the engine hard.
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Unread 08-31-2009, 04:47 PM   #10
bigredisb
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I understand what it does and that you should get some but this looks like a diesel rolling coals. Its bad! I talked with a carb shop this afternoon and he had described that some guys back in the day would enlarge the passages from the accelerator pump into the intake of the carb for modified engines?? I mentioned to him that a X amount of CFM is all a carb will flow and he completely agreed that this mod does not really do anything. Maybe mine is a bastardized carb. The choke is completely off, and I am running a 14 inch brand new air cleaner so I dont think its a lack of air.

Houstonmat,
I would really like to find out if a accelerator pump and power valve fix your issue.
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Unread 08-31-2009, 07:06 PM   #11
bigredisb
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Well thanks to your tips I fixed my problem. I pulled the power valve to inspect and noticed that the new valve I received has about half of the spring tension my original one had. I put the original in and black smoke problem fixed. I still had the surge so I readjusted my mixture using a vacuum gauge and have her holding steady at 21.5 for vacuum @ 1 3/4 turns out on my mixture. Still had the surge so I put the accelerator pump linkage at the throttle up to the top hole with the other end in the hole nearest the accelerator pump. Surge gone! Runs like a champ. I turned my fuel filter so the return is up and my hard start problem is gone as well.

Houstonmat I would bet yours has something to do with the accelerator pump.
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Unread 08-31-2009, 08:53 PM   #12
OldSkull
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Acceleration problem

Quote:
Originally Posted by bigredisb View Post
Well thanks to your tips I fixed my problem. I pulled the power valve to inspect and noticed that the new valve I received has about half of the spring tension my original one had. I put the original in and black smoke problem fixed. I still had the surge so I readjusted my mixture using a vacuum gauge and have her holding steady at 21.5 for vacuum @ 1 3/4 turns out on my mixture. Still had the surge so I put the accelerator pump linkage at the throttle up to the top hole with the other end in the hole nearest the accelerator pump. Surge gone! Runs like a champ. I turned my fuel filter so the return is up and my hard start problem is gone as well.

Houstonmat I would bet yours has something to do with the accelerator pump.

I also adjusted the accelerator linkage and pretty much fixed that problem. Now after all this I still want to make it perfect....well as good as I can. Now sometimes I get the feeling I am still accelerating when I am letting off the gas. kind of feels like a flat spot. It will go if I give it a lot of gas, but after accelerating and I let off the gas I can feel a point where it feels like I am still accelerating. Does that make sense? Should I adjust the air/fuel ratio?
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Last edited by OldSkull; 08-31-2009 at 10:30 PM..
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Unread 08-31-2009, 11:07 PM   #13
JeepHammer
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Not from Holley, they check ALL Passages before rebuild.

What may be happening is the power valve is blown or tore up, that can cause some Issues...

Since your carb is 7-8 years old, wouldn't hurt to invest in a rebuild kit.
Runs about $20.

What I would do if I were you is,
1. Run the idle mixture screws all the way IN.
Count the turns they both go in to make sure they are EVEN.
If the engine runs with the screws all the way in, then you have a problem with an enrichment circuit, probably power valve...
But could be throttle blade adjustment, too high of fuel pressure, or leaking needle and seat.

2. I would turn the idle mixture screws back out to about 1.5 turns or so,
Then I would drive the vehicle with a vacuum gauge attached.
What ever the vacuum reading is at part trottle cruise, about 55 on flat ground,
Record that vacuum reading.
You will need it to select the correct power valve.
Your power valve opening point should be about 2 In.Hg. BELOW your PTC vacuum reading so it's not open while you are at PTC, but will still open when you tip into the throttle.

3. I would check to see if your vacuum advance on the distributor is working.
You can get a 'Stumble' if your vacuum advance isn't working.

What you really need to decide is if your engine is trying to gain RPM, then dies off,
This would indicated you don't have a long enough duration accelrator pump shot.

Or,
If the engine stumbles immediately, then recovers.
This means you don't have the pump shot happening fast enough.
Slop in the linkage or a bad accelerator pump diaphragm causes that problem.

Then I would consider a rebuild.
Your carb is VERY easy to rebuild, not many moving parts or 'Wear' parts inside it.
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Unread 04-08-2010, 12:44 PM   #14
rkinks35
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Im having issues with my CJ-7 V8 AMC.. The first start up for the day is great it runs hot at 2500-3000 RPMS after 5 minutes I hit the gas and the IDLE drops down to its reg position and idles strong. After I drive the truck and turn it off say at a store. I try and start it back up after a few minutes and it starts and dies in 5 seconds. Then it seems to not want to start or have any power to go anywhere. I recently started messing with the carb thinking that maybe its stuck or something. After letting it rest for sometime and moving the carb around I was able to start it. The IDLE was very low and wanted to die. I gased it hard for a while and it finally got enough power to stay strong and get me home. As soon as I got home, I sat there let it IDLE, the IDLE went from strong to weak and then finally died.

Any ideas? PLEASE HELP
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Unread 02-02-2012, 12:43 PM   #15
CURBSTOMPING
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OK heres the issue 78-cj7 304 first i thought it was a fuel pump not it. the carb is getting fuel idles for about 30 seconds then dies. should i just go straight to a rebuild or what can other possibilities be. i was reading other posts but i have no clues about carb's.
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