Pesky Gremlin hunt!

Well, I've been driving the CJ as a daily for 2 and a half weeks now. I'm lovin' it. But it's runnin like a heap of you-know-what. The 258s got a persistant skip, and dosen't like to stay running at a stop sign.
Today I got all the tune-up parts. Plugs, rotor, cap, wires and air filter. and put 'em in. But it really diden't make a differance. It runs good cold, but gets porgressivly worse as it warms up.
I have the EGR disconnected, and most of the other emissions stuff is long gone.
I did notice that the vacuume advance still runs through the device that switches it from ported to manifold vacuume depending on the engine temp (switch down on the engine block). My thought was to just direct connect the distributor to the manifold vacuume, and get rid of all that other junk, but I'm not sure if that's the best idea.
I'm also going to get a new fuel pump tomorrow, as I'm extremely suspicious of it leaking fuel into the crank, an I'm giving it another oil change (with some Lucas).
There are no apparant vacuume leaks, and the compression seems good, the coil IS pretty old as is the old Dura-spark module...
Anybody have any hints to add to my current line of diag??
A carb rebuild is a little down the road, but I'm not convinced it really needs one yet.

 

My 258 sounds just like that. At low RPM's it sounds really scary. Hook up a vaccum gauge and make sure your mixture screw on the carb is adjusted as good as it gets. Having it right where it should be helped me alot.

 

Could be that the choke isn't opening once it warms up or you may have to adjust the idle circuit. By persistant skip, do you mean a flat spot? How well does it maintain speed and accelerate once warmed up?

 

An '80 will have the 2V Carter BBD. This is a carb that has some well-known problems. If you search on the net, you'll find several places that will tell you how to drill out the idle tubes, and something called the "nutter bypass" that bypasses the "electronic" mixture control on these carbs. My '77 came with the BBD (no mixture soleniod though). It had the typical dying at idle problem though. I fiddled with it a little bit, then replaced it with the Motorcraft 2100 carb. I'll be going TBI ASAP.

 

It sounds to me like you have carb issues and nothing more.

If that vaccume switch on the block is working and when the motor is fully warmed up you are getting ported vacuum (vacuum increases with throttle) to the vacuum advance then leave it alone. If you have to choose one, give the advance ported vaccum instead of fulll manifold.

Also check for vacuum leaks and plug em up.

I would then rebuild the carb sooner rather then later. I would hold off on the duraspark module and the coil they are most likely fine, save your money. If they are fualty the motor usually will not run or will quit running.

Not sure what you mean by gas leaking into the crank...Never heard of that. I don't think you have an onboard computer (but not 100%) so a nutter bypass is not necessary. As far as drilling out the venturi's in the carb get that done when you rebuild it and it should run like a top.

 

I have the non-electronic carb. No solenoids. just an electric choke.
I have checked for vacuume leaks by spraying carb cleaner around the carb and intake and pinching off vacuume lines. It all seemed good. even the throttle shaft area.
Today, after work, I replaced the suspected fuel pump. along with a new filter for good measure. and changed the fuel saturated oil. It ran better for a bit, but was right back to being cruddy on the way home.
It acts like it loads up at anything below 2000 rpm.
I ordered the carb kit earlier today, so I took of the carb tonight, and I'm taking it in to work tomorrow to rebuild it.
When I got the carb off, there was a pool of gas in the intake. So I'm pretty confident I've found the problem.
MA74CJ5, The fuel pump problem is that the diaphragm in the pump can go bad and allow fuel to leak into the crank. I've seen it more than once, and the car was still running fine other than bad oil pressure and engine noise from the oil being thinned out.
The new pump was only 15$ so it was cheap piece of mind. I'm not so convinced that that was the problem, so I'll keep the old one for a spare.
Thanks for all the tips. I'll go searching for carb info tonight, and be ready for tomorrow
Here's hoping!!!

 

I had a problem once that the carb float was stuck wide open and the fuel was just pouring into the motor and it diluted the oil real bad. It ran like crap and my oil was like 2 qts high. I rebuilt the carb and drained the old oil out and it ran great. Make sure you drain that gas saturated oil otherwise it will scour the internal parts of oil and you will have major unhappiness.

 

Yes, I'd have to look at my BBD, but a BBD may overflow the bowl into the throat of the carb. I'd be surprised that it would even start, much less run, if that's the problem.

You definitely should not see liquid gas anywhere except the fuel inlet and float bowl.

 

Update... Definatly did not have a stuck float needle. But the float level was off a bit. I rebuilt the carb, making sure to clean out the idle tubes. It was cruddy, and a little out of adjustment.
I installed it back on the Jeep late tonight (first chance I had) and fired it up. No dripping from the venturies now. and it seemed to be running better, until it started to warm up. then the skip came back.
It IS better, but not good. Tomorrow I'm gonna double check the timing, and double check for any vacuume leaks... I'm getting a bit frustrated.
Lynn, It does have a canister, but the only hoses hooked up are the vents. The vacuume side is disconnected, so I know it's not an issue.
I diden't get a chance to test drive it with the new carb in it yet, so I'll take a drive and report back.
Thanks for all the ideas. We'll get through this.

 

OK. I got to go for a drive today. first drive, running progressivly worse as it warmed up. Skipping at idle, but not dying out at every red light like before. Once you get it revved up a bit it's ok but not really good.
So I come home to fiddle... I check the timing, ok, then I try backing the idle mixture screws out a bit more to see if that helps any. All data I've found on setting these things is really vague, so I had them set to 2 and a half turns out to start. I crank em out another turn, and the skipping gets better, another turn and its better yet, more than that dosen't help, so I turned them back in a bit.
Now it runns pretty nince. an occasional skip, but not constant, and it's not loading up or trying to die at idle. I'm happy. It even smells "eggy" outta the tailpipe now instead of smelling like half burnt gas. I think the cat is trying to work (hope it's not gonna melt down now).
So there ya have it. It was mainly the plugged idle tubes, and mis adjusted mixture screws.
I'll keep ya all updated on how it continues to run.
Thanks all for the help.
Happy turkey day!!!!