Engine wants to stall

[JeepCJ5]

So I just put my fuel system back together. I took out the gas tank so that I could weld in repairs to my rear tub.

I replaced the fuel tank, sender (gas gauge works now!), filler hoses and almost all the rubber fuel lines (all of the ones in the rear, I have a couple more to change in the engine bay.

I had previously installed the Weber 32/36 carburetor and put about 50 miles on the Jeep before I dropped the tank.

While I was working on the rear, I also installed the Holley fuel regulator, since I read in many places that it is needed for the Weber Carb.

When I got everything together, the engine started right up and idles fine. The problem I am having is that if I give the pedal a quick push, the engine wants to stall. If I slowly press the pedal, the engine responds great and revs up no problem. I drove my jeep around the block with no problem.

One last thing. The pressure gauge on the fuel regulator is jumping back and forth pretty wildly at idle. It seems to be centered around 4 psi, but when I go to adjust the regulator, it moves even more wildly going from 0 all the way above 10.

I don't remember having this problem before adding the regulator, so I plan to bypass it and see if I still have the problem, but I wanted to see if you guys have any advice.

 

[Torxhead]

Good choice on ditching the regulator, that way you can tell just what effect it has. Usually when the engine lags when the pedal is pushed it is the accelerator pump on the carb. There might be an issue with a low idle or initial timing setting, so make sure you know where they are set.

 

[81CJ7WY]

Accelerator pump is for counteracting the momentary lean condition of accelerating the engine speed. If engine stalls, and then relights, the fuel air mixture is more than likely lean, or not enough fuel to the amount of air going through the carb to hold that ideal 15 to 1 ratio.

Is this a new carb? If not then a worn gasket on the pump plunger, air intake leaks, idle mixture incorect set or caused by obstruction in the air regulation inside the carb, and low fuel bowl level, are contributing cause to a lean mixture.

Hope you don't have to take your carb apart.

 

[JeepCJ5]

It's an almost brand new carb. I just bypassed the regulator and it is still missing. The engine also has a sort of pup-pup-pup-pup sound at idle.

I'll double check the timing tomorrow. The last time I checked it, it was within specs. I'll also swap back to the previous fuel filter, just to make sure the new one is ok.

Thanks for your help...

 

[81CJ7WY]

That's unfortunate to have a new carb and then problems with it.
It sure does sound like a lean condition momentarily when you accelerate. The gasket between the carb and mana fold checks out ok, or new I assume. The linkage between the pump and throttle cable is tight? And the pump squirts immediately when moved? thinking there might be a delay from when you open the throttle plate to when gas gets squirted down the throat. Or some blockage of the accelerator pump causing a momentary lean condition. Or possibly a vacuum hose leak, cracked, or not attached. But perhaps I'm to simple thinking here.

If it was rich condition it would sputter, die, or lope at idle.

After I cleaned my carb, removed the pollution stuff, and plugged the holes, I was able to get the idle way down, I should of checked the speed but it was amazingly slow. I tuned up both barrels at that speed as it was easily to hear the rpm change with the rich lean adjustment.

 

[Lumpy Grits]

Look for vacuum leaks.
Check the idle mix setting.
Check the ign timing.
Every carb has to be tuned for the engine it sits on.
LG

 

[JeepCJ5]

So. when all else fails, use your noggin...

I tried to remember everything I did to the engine while I had the fuel tank out. I remembered that there was a cap on a nipple above where the EGR used to go that was in poor shape - dry rotted. I went ahead and replaced it with a tight fitting cap. This afternoon, I started the engine, and removed that cap - voila! The engine went back to sounding great and my hesitation problem went away. So my question is this - what should I connect to this nipple? When I got the jeep, there was no emissions equipment left except the charcoal canister. Right now, I have the fuel line coming from the pump, going to the filter. I have the return on the top and the fuel goes to my regulator set at 3.5psi. It then goes into the carb. I have the vacuum from the carb going to the distributor advance. I have the breather in the back of the valve cover going to the air filter inlet. I have the PCV valve in the front going to the nipple on the base of the carb. And finally I replaced the charcoal canister with the only one I could find - it only has three nipples - Tank, purge and air. I connected the tank nipple back to the fuel tank vent and the purge up to the carb. The Air line is unconnected. I searched for months, and tried every part number I found on the web. Napa, Rock Auto, Etc... this is the canister I ended up with:

https://www.amazon.com/Standard-Mot...Standard+Motor+Products+CP1039+Vapor+Canister

So the only vacuum I have running is the dist. advance.

Here's a photo of my setup and also of the unconnected nipple. I searched through my Haynes manual, but I can't find what it is called.

Thanks for any guidance you can provide as to how I should hook things up...

 

[Torxhead]

I looked at my '86 for a source to that unconnected nipple and mine is blocked off also. Maybe for something emissions related. That "air" connection on the canister has me puzzled also.
Evaporation Canister, Here is a page that tells how the later CJ canister is setup. Anyway, I just wanted to suggest using the neopreme(I think that what they are) vacuum caps as they last a bit longer.

 

[JeepCJ5]

Thanks Torx - is yours tightly capped? As soon as I put my finger over it, the engine starts running poorly. The old cap that was on there was a loose fitting cap, so I guess it let some air get in there.

I think I have the purge on my canister going to the wrong place. According to that site, it is supposed to go to manifold vacuum. Maybe the "Air" connection is equivalent to the purge signal line?

Thanks for that link - I've been there before, but I'll go through it all again.

 

[JeepCJ5]

I found this photo which shows it connected to the original air filter system:

 

[Lumpy Grits]

That threaded fitting pointed at the fender goes to the power brake booster. The uncovered nipple is for manifold vac. Cover/plug both if you aren't using them.


LG

 

[JeepCJ5]

Here's another where it is connected to something else - maybe the PCV?

 

[JeepCJ5]

That threaded fitting pointed at the fender goes to the power brake booster. The uncovered nipple is for manifold vac. Cover/plug both if you aren't using them.


LG

Interesting - If I plug it, the engine runs worse...

Here's a diagram with it going to the PCV:

I think I'll try that out.

 

[Lumpy Grits]

Bet the idle mix screws are way out to compensate for the vacuum leak from that fitting.
LG

 

[JeepCJ5]

Bet the idle mix screws are way out to compensate for the vacuum leak from that fitting.
LG

It only has one idle mix screw( and the fast idle screw). I don't think it is way out, but I will redo the instructions to set it and see where it is at.

 

[Posi]

The arrow points to a port that supplies vacuum to the thermostatically controlled air cleaner (TAC) system. There is an air valve in the cleaner housing that opens during warm-ups. The manifold vacuum is controlled by a thermal sensor in the air cleaner housing. The thermal sensor allows manifold vacuum to open the vacuum motor allowing warm manifold air in on cold starts, and closes when engine is warm.

 

[Lumpy Grits]

It only has one idle mix screw( and the fast idle screw). I don't think it is way out, but I will redo the instructions to set it and see where it is at.

If you don't have one-A vacuum gauge is the best way to set the idle mix.
Have you put a wrench to ALL of the manifold bolts?
LG

 

[JeepCJ5]

If you don't have one-A vacuum gauge is the best way to set the idle mix.
Have you put a wrench to ALL of the manifold bolts?
LG

No I haven't touched the manifold bolts - I'll do that and pick up a vacuum gauge also.

Thanks for the info Posi...

 

[JR74CJ5]

The arrow points to a port that supplies vacuum to the thermostatically controlled air cleaner (TAC) system. There is an air valve in the cleaner housing that opens during warm-ups. The manifold vacuum is controlled by a thermal sensor in the air cleaner housing. The thermal sensor allows manifold vacuum to open the vacuum motor allowing warm manifold air in on cold starts, and closes when engine is warm.

So if his engine is running crappy when it's plugged, does that mean it's trying to suck warm air in on warm up and not getting anything or (starving for air / vac)? And if it auto closes when warm in this case, as he's said when capped the engine runs crappy, then it should theoretically run crappier the warmer the motor gets even when uncapped as it auto closes the valve internally yes?

Something in that thing gummed up and not allowing correct operation?

Just trying to understand the connection as I don't have one of those doohickies... (well, CTO switch is similar, but not same...)

 

[Posi]

For it to work properly one has to have a stock air cleaner housing, and all the parts that go with it, thermal sensor, vacuum motor, and vacuum hose. The OP has a weber carb with no means to introduce warm air.

I was simply explaining the purpose and function of his open factory vacuum port. Without the factory air cleaner housing that particular port should be sealed.

He needs to get a vacuum reading and post it up.