Build Thread Treblehook's 79/85 CJ7 Circus!!

Build Thread Treblehook's 79/85 CJ7 Circus!!
Rescue Diver said:
S~~~ The only things it could be are, fuel filter, fuel pump, fuel line either being crimped somewhere restricting flow, or having a small leak between the tank and pump causing it to suck air, or maybe your gas tank isn't vented properly causing a vacuum that isn't allowing the pump to suck fuel? ~~~
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Might be a very low float level causing the engine to starve too. As RD said - easy way to check for the bowl to be empty is look down the venturis and check for fuel squirting out of the accel pump nozles.
 
CJ said:
Might be a very low float level causing the engine to starve too. As RD said - easy way to check for the bowl to be empty is look down the venturis and check for fuel squirting out of the accel pump nozles.
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When the float bowl is too low for fuel to be drawn out of the venturis by the engine's vacuum, it might still squirt some gas out of the accellerator pump nozzles when pumping the throttle. The only way to really be sure is to remove the very few screws that hold the air horn(float bowl cover), disconnexct the choke rod, take the top off and see where the float level is set, or how much fuel is in the bowl after it dies. It would be nice if those old Motorcraft carbs had a sight window in the bowl like a holley, but they don't.
 
One other thought I just had that would fit the symptoms he's describing is a very big, intermittent vacuum leak. If it's suddenly leaning out and dying, but he can feather the throttle a few times to keep it running once in a while, it could very well be the carb base not being bolted tightly to the manifold, or maybe a really big crack in the power brake or PVC hose.
 
Rescue Diver said:
One other thought I just had that would fit the symptoms he's describing is a very big, intermittent vacuum leak. If it's suddenly leaning out and dying, but he can feather the throttle a few times to keep it running once in a while, it could very well be the carb base not being bolted tightly to the manifold, or maybe a really big crack in the power brake or PVC hose.
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I think you are on to something! I did notice that I can wiggle (just slightly) the carb on the manifold...do I just tighten it down?

Thanks for all the help. I'll let you know more when I get home and check it out....

Cheers,:chug:
Treblehook
 
TrebleHook said:
I think you are on to something! I did notice that I can wiggle (just slightly) the carb on the manifold...do I just tighten it down?

Thanks for all the help. I'll let you know more when I get home and check it out....

Cheers,:chug:
Treblehook
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If you can wiggle the carb on the manifold, by all means tighten it down. I believe you have a carb adapter to make your Motorcraft carb fit the AMC intake. Remove the carb from the adapter first and tighten down the adapter to the manifold if that's where it's loose, then reinstall the carb and snug it down as well. Do not over tighten the carb base bolts! You can warp or crack the base.
 
CJ and Rescue Diver - Thanks for all the help! So this is where we are at....

I happened to fill up the Jeep with gas on my way home today. Drove home and pulled into the garage -- I could smell gas. I checked the rollover check-valve (RCV) and sure enough there was fuel running down the fuel hose to the RCV. I had replaced those hoses the first day I bought the Jeep, but it apparently wasn't tight enough or something....

More importantly, I wondered why there would be that much pressure in the tank/system. I popped the gas gap and a huge "hssssssss" let off the pressure. No vented gas cap.

As soon as I vented the tank, the leak stopped flowing. I tightened the hose clamp best I could and headed over to Napa (There are 3 parts stores -- Autozone, Napa, and Advanced Auto -- within 3 minutes of my house!). $9.99 and I had an OE vented gas cap (looks just like my old one but with a little hole). Can't hurt right? Jeep was running great. :)

So following the advice above, I pulled the top off the carb to take a look -- it hadn't stalled, but I was curious. Float bowls were "full" at about 2/3 of the way. Everything looked good to me, but then again, I have no idea what I'm looking for. Put the top back on. Thumbed the throttle and watched fuel squirt into the carb. Nothing obviously wrong.... still :confused:

I reluctantly (read: afraid to really screw something up) removed the carb. It was actually VERY easy. 1 vacuum line. 1 PCV line. 1 electric choke wire. 1 throttle cable. 2 brackets. 4 bolts. Done.

I left the fuel line on the front of the carb and set the whole thing on the valve cover.

I was left looking at the adapter plate (Aluminum - Stamped Mr. Gasket, didn't catch the part number). But....

There were THREE (3) paper gaskets stacked between the carb and the adapter plate. All were a little different, the top one was shaped so that it had 2 large holes to match the bottom of the carb. :confused:

I remember the PO telling me that he "made" one of the carb gaskets. Hmmm?

The allen bolts that connect the adapter plate to the manifold were, in fact, pretty loose. I tightened them up, put the gaskets (all 3) back in, and reinstalled the carb.

I was pretty proud of myself....AND....it fired right up! Confidence builder!!

So to check the "massive vacuum leak" theory, I very carefully sprayed some starting fluid on/around the pvc hose - no change.

Then I very carefully sprayed the base of the carb at the adapter plate/manifold...the engine almost immediately died - and then sputtered back to life. I did this a few time, making sure it wasn't just vapor being sucked into the butterflies. Same effect.

Is this normal? Solution?

Good news is that I advanced the HEI timing just a "hair" (turned by hand - tuned by ear) and the Jeep is running stronger than ever and idling much better. I couldn't get the Gremlin to show his face today.

Appreciate any and all input! Thanks in advance....

Cheers, :chug:
Treblehook

P.S. I also replaced my tail light lenses today. I'm a sucker for shiny objects -- and the old one was cracked.

P.P.S. I also put air in the tires -- 31x10.5x15 BFG ATs....what is the appropriate tire pressure for everyday driving? I have them at 32 psi -- they were at 18. Too much?
 
Your carb adapter is probably a Mr Gasket 1934 if I remember the part number correctly. I filled in the crater on mine were it says MR GASKET with JB Weld to make it smooth because it's right about the area were the MC2100 carb seals to it and can cause a vacuum leak. You need to go to the parts store and buy the really thick composite base gasket for a 1971 Ford F100 Pickup truck with a 302. Use it to replace the combination of gaskets that the previous owner rigged it up with between the adapter and carb. It sounds like you still have a pretty nasty vacuum leak from what you described. You think pulling the carb and re-installing it was easy. Wait till yo do it the second time around!
 
Rescue Diver said:
Your carb adapter is probably a Mr Gasket 1934 if I remember the part number correctly. I filled in the crater on mine were it says MR GASKET with JB Weld to make it smooth because it's right about the area were the MC2100 carb seals to it and can cause a vacuum leak. You need to go to the parts store and buy the really thick composite base gasket for a 1971 Ford F100 Pickup truck with a 302. Use it to replace the combination of gaskets that the previous owner rigged it up with between the adapter and carb. It sounds like you still have a pretty nasty vacuum leak from what you described. You think pulling the carb and re-installing it was easy. Wait till yo do it the second time around!
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This?

https://www.napaonline.com/Catalog/...99001+101971+50028+2028016&Ar=AND(P_RecType:A)

Napa Part #: CRB 27429

Thanks!

Cheers, :chug:
TrebleHook
 
TrebleHook said:
Or this?

Napa part # FPG 600941

Sorry for the bad links....

Cheers, :chug:
TrebleHook
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Not sure from the picture. It should be about 3/16" thick.
 
Alright --

Pulled the carb again with the intent of remounting it with the proper gaskets -- more Gremlin hunting....

Unbolted the carb - I am now a pro! - and completely removed it.

What was left was a stack of 3 gaskets on top of the Mr. Gasket adapter plate.



Removed them an removed the bolts for the adapter. With the adapter off, I was still left with a stack -- (top down) gasket, some sort of 1/2 inch spacer, another gasket and a thick corkboard type gasket.


I removed it ALL. Cleaned the manifold surface and decided that I was going to bolt the adapter plate straight to the manifold -- and get rid of all those layers of stuff....

I had the right gasket for between the adapter plate and the carb:


I needed a gasket for between the manifold and the adapter plate. I was hesitant to ONLY use the small paper gasket that I matched up.


So I made one! Bought some cork and just did my best...more to follow!

Cheers, :chug:
TrebleHook
 
Goo job!

One important thing. Test fit the carb, gasket, and adapter combo by bolting them together but not on the intake. Then turn it upside down and inspect it carefully to make sure all sealing surfaces overlap so there is no chance that air can get sucked in somewhere. Pay close attention to the crater Mr. Gasket stupidly puts in the top of the adapter where their name is stamped. Like I said, I filled mine in with JB Weld because the crater just happened to be right on the edge of where the carb base plate seals to it. All of this might explain why the previous owner had a crazy assortment of gaskets, and why it still leaked despite his efforts. You can get by with just the one thick gasket, but just check to make sure it all looks good and lines up well from underneath before you bolt it all to the intake.
 
Rescue Diver said:
Goo job!

One important thing. Test fit the carb, gasket, and adapter combo by bolting them together but not on the intake. Then turn it upside down and inspect it carefully to make sure all sealing surfaces overlap so there is no chance that air can get sucked in somewhere. Pay close attention to the crater Mr. Gasket stupidly puts in the top of the adapter where their name is stamped. Like I said, I filled mine in with JB Weld because the crater just happened to be right on the edge of where the carb base plate seals to it. All of this might explain why the previous owner had a crazy assortment of gaskets, and why it still leaked despite his efforts. You can get by with just the one thick gasket, but just check to make sure it all looks good and lines up well from underneath before you bolt it all to the intake.
Click to expand...

Well damn Rescue Diver! Where were you 3 hours ago??

When I meant "more to follow" I meant "I've gotta upload all the photos of what I did so I can post the whole story!" So here it is....

I bought some cork gasket and made a template from the stock paper gasket:


I then lined it up on the adapter plate and cut the center out to match:


I marked the wholes and used a very sharp 5/16 drill bit to actually drill out the cork where the holes needed to be -- worked PERFECTLY -- but I had to punch all the way through and that left some holes in the chair I was using. I actually made 2 gaskets, since the first wasn't just right.

In the end it looked pretty good:


Without all the gaskets and spacers between the adapter plate and manifold, I realized that the bolts for the adapter were too long (1.5") and would bottom out. I went to the local hardware store and bought some shorter ones (1").


I sprayed the cork gasket with Permatex Copper. It's recommended for carb gaskets and I thought it couldn't hurt.

I also bought new 2" bolts to bolt the carb and new thicker gasket to the adapter -- but I don't have a picture.

Bolted down the adapter. Stacked the new gasket and carb and bolted that on. So far so good.



Got all the lines and linkage put back on -- and turned the key -- VVVVVVRRRRROOOOOM!! Started right up and actually seem to idle slower and better -- I must have done something right!

Just to be sure, I sprayed a little starting fluid on the back of manifold/carb -- nothing.

Sprayed the front --- sputter. ^&^*&%^%*^&$&%$%^&*)&*(&%(*I%&^$^&&@$%#%$$#^%$##^%$#^%$&%$#^$%#$^&*$$%^#$@##%$#^&#%$#^$&%*&^$&%&&^%*%&%^$*&%(&%*%%*%*(..........:mad:

Apparently my gasket didn't work. It helped but my guess is what Rescue Diver said above -- the imprint on the Mr. Gasket plate is just too close to the lip where the gasket meets up.

I drove it hard to test it out....I was really into it and it ran VERY STRONG. No stalls. No sputter. No spark-knock. So I may or may not pull it apart to try again.....

It's tempting since I am getting good at it!!!! :):):):):)

Thanks for all the help! We'll see what's next......

Cheers,
TrebleHook:chug::chug:
 
Great job Trebelhook!

It's getting closer if the idle is lower since vacuum leaks cause a high idle, but I would definitely find and fix that last tiny little vacuum leak. If it's sputtering when you spray where the carb base meets the adapter in front, you have a leak, most likely at the crater where you said. In my world, no vacuum leak is acceptable. It makes it impossible to tune the carb correctly, and it kills your throttle response.

One pointer for future gasket making. A great way to put bolt holes in gasket material is to use a spent bullet shell casing, a hammer and a block of wood to punch a perfectly round hole. :chug:
 
P.S. That is one seriously thick gasket you have between the carb and adapter! It almost looks like a plastic spacer. What's it off of? Mine isn't half that thick, and it's a little longer and wider than the adapter so it sticks out around the edges.
 
Rescue Diver said:
P.S. That is one seriously thick gasket you have between the carb and adapter! It almost looks like a plastic spacer. What's it off of? Mine isn't half that thick, and it's a little longer and wider than the adapter so it sticks out around the edges.
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Shell casing - brilliant! I'll throw one of my .40cal shells in the tool box - should be right about 5/16.

The gasket is Fel Pro part #....forgot it. I'll post it later.

Well I am just about SICK of this Gremlin -- Jeep fired up this morning better than ususal and idled pretty nice after a little warm up. I was pretty pleased....

Hit the highway for the 6 minute drive the base - no issues - smooth.

Pulled in the gate, showed my ID card, pulled away and....the damn GREMLIN stalled out the Jeep again. EXACT SAME SYMPTOMS as before I changed the manifold base gasket set-up.

I pulled over, turned it over and pumped the gas. After about 15 seconds -- fired right up. Feathered it for a second and it was idling just fine. Drove off like nothing was wrong.

I am starting to wonder if it's just a vacuum leak at the base or if there is something else wrong with the carb.

Ideas?

Cheers, :chug:
TrebleHook
 
Well it definitely sounds like you had a serious vacuum leak, and still have a small one to resolve, but once you've taken care of that and it no longer sputters when you spray at the base, it's time to go back to looking into possible fuel delivery issues.

Get that last leak fixed, then we'll look into the float level, needle and seats, fuel pump, and fuel lines.

When it finally starts back up after dying, does smoke come from the exhaust or does it smell really rich? Just trying to make sure it's not flooding for some reason.
 
Rescue Diver said:
Well it definitely sounds like you had a serious vacuum leak, and still have a small one to resolve, but once you've taken care of that and it no longer sputters when you spray at the base, it's time to go back to looking into possible fuel delivery issues.

Get that last leak fixed, then we'll look into the float level, needle and seats, fuel pump, and fuel lines.

When it finally starts back up after dying, does smoke come from the exhaust or does it smell really rich? Just trying to make sure it's not flooding for some reason.
Click to expand...

I'll go at it again tonight and see if I can get that leak fixed....

Then the Gremlin hunting can start anew --

When it finally starts back up after dying, I am usually screaming at the top of my lungs about what a total POS this thing is...so any smoke may have been coimg from the top of my head!;)

But seriously - I didn't mention this before -- when I do start up the motor it tends to shoot a liquid out of the tailpipe. Just a spatter of what smells like water and soot. I'll keep my eyes peeled, and I'll get you a pic of the float bowls...

Again, THANKS for all the help. Let the adventure continue....

Cheers, :chug:
TrebleHook
 
TrebleHook said:
I'll go at it again tonight and see if I can get that leak fixed....

Then the Gremlin hunting can start anew --

When it finally starts back up after dying, I am usually screaming at the top of my lungs about what a total POS this thing is...so any smoke may have been coimg from the top of my head!;)

But seriously - I didn't mention this before -- when I do start up the motor it tends to shoot a liquid out of the tailpipe. Just a spatter of what smells like water and soot. I'll keep my eyes peeled, and I'll get you a pic of the float bowls...

Again, THANKS for all the help. Let the adventure continue....

Cheers, :chug:
TrebleHook
Click to expand...

If you want to pinpoint exactly where the vacuum leak is, try pushing play dough in the edge of the base to plug the leak one small area at a time while it's running and spray carb cleaner to see if it still sputters. My money is on the crater in the adapter. The only bad thing about the MC2100 carb is the base isn't just a smooth surface between the butterflies and the outer edge. It just has a thin ridge around the perimeter that seals it to the intake or in this case, the adapter. If the gasket isn't squeezed tightly between the outer edge of the carb base and the adapter all the way around, you'll have a small leak that can really mess with you.
 
I'll be out of the country for a week starting Sunday, so if any questions come up while I'm gone, I'll address them later. Unless I get really bored in paradise and break out the laptop. :D
 
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