Carb Issues?

[phyrph0enix]

[1984 Jeep CJ7 AMC 258 i6 / 4.2l , 5 speed, stock wheels/tyres/ride height]

1st issue:
Car ran great! Then bean to miss at idle. Compression test showed about 95psi on every cylinder. Manual turning of the crank showed no rotor spin for ~10º. Rotor could be jiggled up and down about 1/16".

So, that led me to these repairs so far:

NEW:
timing chain and gears
distributor
cap
rotor
plugs
wires

others:
valve cover gasket
F+R pads/shoes/calipers/cylinders/hardware
parking brake cables/hardware

The Nutter Bypass was done by the PO... despite it being a total mess, It looks like he got the basics right.

My new problem:
The car starts on a dime and idles at 8ºBTDC. The vacuum advance works. Also, after I finished with the above repairs it ran flawlessly for about 3 days. Now, it sputters and pops at idle but remains fairly constant at 700rpm (±10). When it's shifted into gear and load is applied, the engine bogs down but will kick on and off jerking the car down the street.

What it feels like:
Calm idle at stop light. Apply clutch, shift into 1st. Release clutch to bite and bring RPMs up. **Popping begins and RPMs drop then shoot way up and the car lurches forward and revs hard them RPMs drop and shoot up again. This occurs through every gear and will fluctuate from bogging to revving about once every 3-5 seconds. The minute load is removed idle resumes and is fairly smooth. Essentially, the car gallops down the road...

Since drafting this novel I've been back out. messed with the carb and now it sputters slightly at idle and wants to bog out even without load applied. This led me to think it's a carb issue.

Any ideas?

Also, can anyone identify this carb? It doesn't look like the "carter bbd" I googled but doesn't say anything on it either. If it's my problem, I'd like to know what I have to rebuild or replace... (so I don't replace it with the same thing...)

 

[JR74CJ5]

MC2100 or MC2150 I think... Good news if it is, don't replace it... Great Carb for wheelin...

Looks slightly different than mine, one part missing, but basically looks the same.

Could be few things:

Fuel Related:
Hows your fuel flow looking? Have you checked it? Possibly Leaking fuel line (probably not...) or clogged filter, pump failing, re-build needed on carb... etc.

Vac Leak:
Self explanatory

Air:
Hows the air filter? My Jeep was running like for a while, kept thinking bunch of other problems... Missed the very easy thing. Bought K & N filter, yeah... no more prob. (in that d4epartment any how )



~ JR

 

[phyrph0enix]

Hows your fuel flow looking? Have you checked it? Possibly Leaking fuel line (probably not...) or clogged filter, pump failing, re-build needed on carb... etc.

Just replaced the tank and lines to the pump, also the filter and return lines. Could be the pump... but just watching and had revving shows fuel squirting every time... don't think it's fuel-in...

Vac Leak:
Self explanatory

Actually, I've had my questions about this. There's one vacuum line and it goes to the distributor. What about the PCV? There's nowhere to plug it in unless it draws from the same port as the brake booster. Does it!?

Hows the air filter? My Jeep was running like for a while, kept thinking bunch of other problems... Missed the very easy thing. Bought K & N filter, yeah... no more prob. (in that d4epartment any how )

FACEPALM... I'm going to go look at this RIGHT NOW... I'll let you know how it goes......... MAN I'll feel stupid!

 

[JR74CJ5]

FACEPALM... I'm going to go look at this RIGHT NOW... I'll let you know how it goes......... MAN I'll feel stupid!

Don't get me wrong, I'm really hoping it is that easy for you, but generally it will not act quite as bad as your describing... I on the other hand went mud bogging and up on the trails a few times without checking it so it was very bad by the time i replaced and made a huge difference...

May be a portion of your problem though...

As far as vac... You'd have to wait for someone with that model engine... I only act like I know it all


~ JR

 

[phyrph0enix]

Alright, I removed the air cleaner... It still bogged out... But worse!

The plate on the top of my carb is quite floppy too. It's not connected to anything! There're also no wires for a choke or anything.

So I messed around with it. As I close the top plate, the idle speeds up. As I open it, it begins to sputter. Plus, when I rev the motor, the sucking sound is REALLY LOUD!!!

If I had the $$$ I'd just replace it and be done with it!

 

[JR74CJ5]

with the motor running have you tried spraying a carb and choke cleaner around the mounting plate to check for vac leaks there? (you know... if leaking, the motor will bog down when you spray there... etc)

The carb is very easy to rebuild... as i understand it, one of the easiest.

I found a very good write up on the re-built procedures somewhere... think it was a ford ranger forum... Search for MC2100 and you'll see a load of pics and info on it. Double check it looks like yours in person.

May also be timing or fuel mixture???

You mentioned re doing distributor and such... have you checked to make sure you're on TCD#1 rotor correct position etc?

 

[phyrph0enix]

Haven't checked for a baseplate leak yet... Good idea! The gasket looks new, but when has that ever meant anything?

Thinking out loud... I Just replaced the timing chain and both cam and crank sprockets... I don't think that's the issue- I timed the distributor to 0° on the front plug wire (#1) and advanced it to 8° @1600rpm w/ advance blocked. Then it ran perfectly for 3 days.

I guess my hunch is the carburettor... I put a fuel system cleaner in the gas tank and have run through about 3/4 of that tank. Maybe (hopefully) it gummed up the carb.

I guess I'm also trying to get rid of my current carburettor, as I have a pretty good bead on a Holley for über cheap... I love Holley carbs!

 

[JR74CJ5]

if u do go holly carb, i think u may need a pressure regulator for fuel line and possibly different style filter as well...

 

[phyrph0enix]

if u do go holly carb, i think u may need a pressure regulator for fuel line and possibly different style filter as well...

GOOD TO KNOW!!! I had no idea!!! :O

 

[JR74CJ5]

I think it may depend on which carb, but ive read they like to run at a consistant 3 or 5 psi, and since regulated separately the return line type filters ( which u may or may not have) do not work well with it... Im am not sure of that though... Use advanced google search above and type in holly... Pleanty to read on this site re holley / mc 2100 etc