Running Poorly At Idle

My 59 cj5 stock with F134 has been running very bad at idle lately. It used to be perfect in every way. Has never sat for more than a month without use as long as I have owned it. About 4 years. I rebuilt carb about 3 years ago.

I don't know why or for how long but one of the first things I noticed was my timing was pretty far off. I reset it to 5btdc and it was steady not jumping around then I noticed my idle speed was too low so I brought it up to about 700 and it still is rough I have about 20 inches vacuum measured at intake below carb.

I measured fuel pump pressure it's 4 psi at all times and held pressure even after turning off. It's an original dual vac fuel pump ac4693 bought nos off ebay about 3 years ago I do have a modern plastic type fuel filter that's been on about 4 years I removed the hose past it and let it gravity flow onto ground and gas was coming out I don't know if it was proper flow but it was flowing

I don't smell any fuel in the oil

Removed float cover from carb and saw no debris inside the carb.

Removed vacuum lines only below the carb and installed my vacuum gauge there. Didn't block any other vacuum lines.

Saw my dwell was 35 degrees so I changed it to 41.

Noticed my points looked light gray in color, corrosion?

Installed new spark plugs. Old were pretty black

Did compression check and thought they were pretty good in order
1 was 135
2 was 138
3 was 139
4 was 135

With oil didn't change much but I'm not confident how much or little I put in using an old press the bottom oil can

Wet
1 140
2 146
3 135
4 141


I removed the fan belt to spray starting fluid without the fan blowing it around and I couldn't find any leaks

Other than just doing tune up parts cap rotor condenser spark plugs I'm running out of ideas to check

????

 

It used to be recommended that a full tune up be performed annually. It has been how many years since the last one? Three to four years is plenty of time for points to wear, condenser to loose capacity, plugs to wear out. I think you get the drift.

 

You said the plugs were black, that could mean the carb is letting too much fuel in. Is the float bowl too full when you opened it? Does it smoke, black smoke? Just suggestions. Something else to check, take the cap off, make sure the points are closed, turn on the ignition, hold the coil wire close to a ground and open the points with a screwdriver, you should have a bright blue spark that will jump 3/8" or more. that will tell you that the coil is good. Just trying to help. Check the advance in the distributor, make sure it is not stuck, there is a reason the timing was off.

 

Water in gas? Might check voltage through ballast resistor and coil to dist.

 

"Noticed my points looked light gray in color, corrosion?"

I don't see where you cleaned (or replaced) the points), although you say they look oxidized?? Why not?
Points would be a very basic thing to do, and cap-condensor-rotor are simple cheap insurance.

Settting timing is only valid if the points are put in spec first.

These are the most basic tune up items - on an annual basis.

 

Might try upping the idle speed to 800 or 900 rpm.

And it could be something as simple as the gas you are buying is sub-par.

 

Can you post a video of it idling so we can hear and see it?

 

Well after hearing your suggestions I went out to take a video of it idling poorly and it's idling perfect at 700 where I figure is a good speed. I don't know what exactly changed but last night it was still running bad and today it's now fine?

But I went to buy new cap rotor condenser and points. I only got points and condenser because they had to order the rest and I was going to replace one at a time to see if I could find the problem but for now there doesn't seem to be a problem.

And yes it does seem to smoke a little black

I also noticed today that watching fuel bowl on my fuel pump. Air bubbles are coming up near the inlet fitting on the pump so I must have a air leak that needs taken care of. Currently it has a section of steel line to near the pump and then rubber line-modern style filter-then rubber line and then to the pump.

Probably tomorrow when I get the cap and rotor I will get hard line to go straight to the pump and then install a old school ceramic filter near the carb

 

Fuel pump bowls will always "bubble," that is probably normal.

Why not put the fuel filter before the pump, protect that too?

 

I tried installing the points they gave me today and they are the wrong ones so I will have to exchange them tomorrow.

But I did install the condenser and then it had no spark and wouldn't start, turns out the points were grounding out where they should have been insulated maybe that was my previous rough idle, sometimes it would ground out making no spark then it would work again. Maybe

 

Maybe it was just water in the gas.

 

so it was still doing it again today so I guess I still have a problem but it is much better now that I have replaced the points condenser cap rotor and spark plugs and timed it. I tried to set the mixture screw but I don't really know when its good or what I'm really looking for when its "done" I'm still learning but haven't really learned that yet.

While idling it I had 10.97 volts at the key side of the coil and the battery had 12.7 so the coil isn't getting the full 12v that I think it should be getting

but one thing unusual happened today while I was working on it. I turned off the key and removed the key and the jeep didn't shut off? then I measured voltage at the coil and it still had power which meant even though the key was off the switch wasn't actually off so I think its time for a new ignition switch. I replaced the existing switch about 4 years ago from napa but it looks like its time again

 

So, I would run a hot jumper wire from the battery to the 'key side" of the coil and see how it idles with known-good full voltage to the coil.

Maybe a hinky ignition switch has been the problem all along.

 

Video by SCOTT

 

So during the video the jeep wasnt dying but now while I try Petes idea of a jumper wire to the key side of the coil now the jeep is actually dropping rpm enough to die if I don't give it gas by blip ping throttle.

But the jumper wire to the coil didn't fix my problem.

Is there a way to test the coil itself? Do I measure ohms or something?

 

Also it has 7 volts going the the distributor is that right for a 12v jeep? Internal resistor

 

Sounds like you have a ballast resistor in the lead from the run terminal on the key-switch to the key-side terminal on the coil.

 

I traced the wire from the key to the coil and it's just a normal wire nothing spliced in it. So I don't think it has a resistor in the key side, but it does have lower voltage than the battery so maybe it's a dirty connection at the key switch or inside the key switch.

Being 7 v after the coil I think is how the coils internal resistor is supposed to work so I think that's normal but don't really know