Stalls while driving

Let's review some things please.

There is a timing chain there is not a timing belt at all!

You say it has jumped a tooth, how do you know this actually happened?

This is where things are not clear.

What was done to make it fire back up? Timing chain and gears? Left the chain alone-done something else that made it run?

Any non-OEM mods done to the Jeep over the years?

Two pictures below, my 1977 CJ-5 with a 258 6 cylinder. My Jeep is a daily driver. I rebuilt the engine just before Summer of 1996. (So it was about 21 years that passed when I noticed the chain starting to slap the cover)

Notice how much 'slop' was in the chain and it never jumped timing.

I replaced it (and the gears) with a "Cloyes" double roller timing set, a bit more expensive but with a super reputation. That's been a few years ago, my engine still seems brand new!

I'm fishing for information so that I might help you better.

Your turn,

The Medic

So the long version. motor is stock. No mods. It ran perfectly for four years, then occasionally would just shut off in third and fourth gear. Pull over and it would crank back up. Then one day it started stalling a lot in third and fourth only. Was also back firing from tail pipe. Blew out the back of the muffler. Decided to do a tune up and replace muffler. Plugs, distributor cap, fuel pump. Cracked up. Test drive fifteen to twenty minutes in it shuts off and wont start.. tinkered for a bit, couldn't get it to start and gave up took it to a "mechanic". they were going to check the timing chain, so I told them to replace it while your are in there. They told me it jumped a tooth. I never saw it. They called a week later and said they cant get it to run, they give up, come get it, hence I call they "mechanics." I tow it home, open the choke and it cranks right up! Runs great, then rpm's drop and sounds weird, I will upload a video of sound. I decided to replace coil. Then it wouldn't start. Got an ignition module. Still no start. Then found that the starter solenoid was not getting power. Got power to the solenoid and it cranked right up. Sounds great, running great. then temperature hits 170 ( I watched the gauge) and the revs drop and tone changes at exhaust. blipping the throttle sounds terrible, but continuous throttle behaves okay.

Do you think maybe you could take your breather off, lay your hood against your windshield frame and snap me a left side, right side and overhead picture of your engine. Well lit and full views.

Sometimes I can spot problems pretty quick!

Back to the timing chain- was it or not replaced?

Where is your "numbered" temperature gauge connected to the engine/ water jacket? I'm guessing this is not the original in your speedometer cluster.

The Medic

Temperature gauge is a mechanical that is connected to the engine.

I am told the chain was replaced, I have not opened it to check.

I got it figured out. I got a timing light and the timing was at Zero to 5 degrees advance. Adjusted to 4-5 degrees retarded and runs fine. Drove around about 30 minutes with no problems.

Yours should be set at 13 before top dead center (BTDC) at an idle speed of 600 RPM.

When setting this, the vacuum advance hose to the distributor must be disconnected and plugged off (a small bolt or screw will work).

After the timing is set correctly, unplug and reconnect the vacuum advance hose to the distributor.

Champion RFN-14LY plugs are recommended for your rig. (equivalents will do) I don't recommend using any of these new "high speed" spark plugs, especially the ones with the hypodermic electrodes!

My CJs timing is 8 Degrees BTDC, Below is a pic of how "mine" looks every time the timing light flashes.

Picture 2 is a timing cover removed showing the timing data in full view not covered by the water pump.

Do you know how to check the operation of your distributor's mechanical advance and vacuum advance to insure they do work with your timing light?

What about adjusting your carburetor mix screws correctly?

The Medic

Thanks Medic!
I did unhook the vacuum line when setting the timing.

I will adjust it to 13 sometime this week and let you know.

As far as the distributor operation, I did check that the timing line moved when the motor was accelerated. How much should is change?

I have the carburetor pretty well dialed in. I have been adjusting motorcycle carburetors for years.

CJ MEDEVAC is one of our best! Use 2CarPros anytime, we are here to help. Please tell a friend.

Okay, back again. have the timing and carburetor all dialed in as recommended by CJ Medevac. Drove around town a few times no problems. Today was out on a longer stretch and running 50ish mph in fourth gear when it looses power. More accelerator does not do anything. Pull into a road, back into second gear and fine. Back out on highway, does it again, followed by a tailpipe backfire (small). Heading home motor completely shuts off in third gear, pull over, cranks right back up. This only happens at "higher" speeds in third and fourth gear.

This was happening before and I did a tune-up, plugs, dist cap, fuel pump, filter.

Any ideas?

Thanks Tony

Any parts store might test your ignition module if they do not consider it "obsolete" now days.

I'm partial to "Advance Auto Parts", they are local to me and have never intentionally done me wrong.

Below is pics of their machine, have them test yours 4-8 times, should it fail once, replace that puppy.

Replaced it?

Test the new one the same way before you leave the store. Been there, done that! You may pizz them off with the request. But there is nothing like your Jeep not running and you are tearing your hair out (and tearing the Jeep apart too) all because you are trusting a "new","bad" ignition module you just installed!

According to the AMC service manual and my experiences, To disconnect the module, grab the wires on either side of the connectors and pull hard. Prying and digging at the connectors with a screwdriver will only result in breaking off the locking tabs, then it will not stay connected when re-installed.

Your module will have "blue" plastic around where the wires exit the unit. This might be viewed at the end, or from the other side. (other colors were used by Motorcraft for totally different vehicle applications).

The module can cause backfires, as the ignition is being turned off and back on sometimes when they glitch.

Remember, Mr. Module must be anchored down well, it gets its ground that way. Dangling about is not going to cut it!

Notice the test machine tests the module at different RPMs (read the machine's label).

Last stupid question on this answer, You say patting, giving it gas has "No" effect on the engine while it is in cardiac arrest? No affect period? I'm trying to rule out carburetor issues in my head!

Return with good news!

The Medic

Thanks.
I will pull the new ICM off and get it tested..
When it loses power I can floor it and nothing changes. Would think the mechanical fuel pump would still be pumping.
Left off of my"tune up list" that I replaced the coil and the ICM.

Usually if it's a fuel problem you might get a few surges/ hiccups/ or jolts as the fuel disappears from the intake.

An ignition issue might do the same, if it is total sudden loss of ignition, it will just suddenly die, just like you cut the key off.

Again, from my 2nd answer.

Do you think maybe you could take your breather off, lay your hood against your windshield frame and snap me a left side, right side and overhead picture of your engine. Well lit and full views.

One more idea for now, easy to perform. I went back to another post I answered to a '83 CJ7

Any noticing of hitting bumps, left or right turns, accelerating, decelerating, etc, when he quits running?

This works at times, while you have him sitting static and idling.

Shake/move wires or harnesses around "normally" and while recreating "G forces" in a turn or up and down bumps in the road. See if he cut's off or even skips a little. Wiggle the wires to everything.

Try not to relocate anything until you locate the issue causing it to die (this may not find it at all, but it can and does work if you have a wire issue).

Violent, jerking and over the top flopping the wires about (overdoing it!) may move the problem out of the way for now, but then it might reappear in the future, just when you don't need it to! It's best to find it now if you can, so be gentle with the shaking and wiggling process.

On a previous Jeep I owned, a wire harness ran on top of several flexible hangers (if you will) under the valve cover bolts. The harness ran lengthwise over the top of the exhaust manifold. It took me a while as I never imagined that it could bounce down and kill my ignition. Cranking would bounce it up and slightly away from the manifold and it would be alive again, till I hit another bump just right.

Pic 3 was not intended, forget the text on it! I could not edit it back off of here!

Your turn!

The Medic

So new development/finding. Took test drive before pulling new ICM out. mile or so from home, go to accelerate in third gear, no acceleration. Give it more throttle, no revs. Putt up to stop sign, first and second gear good, third, little sputter, shuts off, little backfire. Pull over cranks back up. Did this about four times going back home. Luckily coming down my street it shuts off but I had enough momentum to roll into the garage. Popped top of carburetor. Bowl is dry. Messed around with it. Seems to have a strong flow when the float is pushed down. So now seems to look like a fuel issue.

Was not bump related.

What is this metal box by the solenoid? Can't find it in my manual.

I know there have been no new post for a while, but did you ever figure anything out? I am having very similar problems.

Hi, Jake.

If you are having similar problems, it could be related to the fuel pump. Does your Jeep still have the original mechanical fuel pump? Also, could you please confirm if your vehicle is the same year, engine, and exactly what the symptoms are which you experience?

Let me know.

Joe

I am having very similar issues. 1978 CJ7 232. Idles fine and runs fairly well until about 10-15 minutes of running time. Once it gets to temperature, about 190 according to gauge, it will still idle fine, accelerates through 1st gear fine, go into top end of 2nd then begins wanting to die. It happens very much so in 3rd gear. Motor begins to die, accelerating further does not help, let off accelerator and it may come back to life or may not. Usually, it begins by bucking pretty bad and have to let off accelerator. Typically have to let the motor go back to an idle speed, "catch up" and downshift to 2nd or 1st gear to continue running with little acceleration pressed. Typically, it will idle forever sitting at the house. If I fast idle say around 2000-2500 rpms it will run for several seconds, then begins to shut off.

Purchased the vehicle in 11/2021. Had water in the fuel when purchased and was not running. Pumped the water and old fuel out of the tank. Have since replaced carburetor (National Carburetor ND1291-NEW AMC and Jeep, 1975-1977, 232"-258", Carter-YF which is what was on it before I purchased and it has the electric choke which is hooked up), fuel filters 1 inline before pump and 1 factory style before carb both replaced 2 times, mechanical fuel pump and upgraded the ignition to HEI ignition. Thinking either the tank still has trash, and the pickup is causing the issue or it's a carb issue. Prefer not to drop tank until last resort. I thought of trying to run the motor off a separate fuel line to a separate tank to try to isolate first. Ran across these posts and thought would ask for advice first. I would like to confirm the vacuum lines are running properly too.

Timing is set at about 12-13.
Distributor vacuum runs to the vacuum port at top of carb underneath air cleaner.
Tried adjusting the mechanical vacuum advance in both directions which made the symptoms worse. Have the mechanical vacuum setting back to the factory setting.
PVC valve is in the front port of valve cover and runs to the carburetor port near automatic choke.
The rear port of valve cover has an oil breather cap.
Second vacuum port on carb at the base is capped.
Factory air cleaner removed and replaced with a small aftermarket air cleaner.
Smog / emissions removed. EGR / CTO vacuum ports are capped.

Hesitate to open the carb and begin making adjustments as I am not very familiar with carbs. I have the rpms set around 650-700rpms, have adjusted the idle and the fuel mixture as best as possible. See pictures for additional insight.

78CJ232,

Normally we would start a new thread for a whole new issue.

Since this is teetering on what the other guy's issue is, continuing here

might help out another soul searching for the same answers

Also looks like you got really involved with your post here.

So, I'm going to continue on this one.

I have a pretty old post that I link folks to. (It still is good!)

I sort of took my 258 tuning and translated it to tuning an 8 cylinder 304.

You will need the 258 parts, the carburetor you have has one mix screw,

but it all tunes the same way.

You will need meters/ timing light/ whatever----tuning by "ear" is

nearly impossible to get things correct, even for an experienced feller.

Look at the pic I post below----- so far, you need to make those changes.

I may have more changes as we go.

That and possible not having done your timing just right, this "fix" may

get you going real soon!

Insure there are no open ports that are sucking air (from outside)

cap them.

I think you will be able to understand what to do in my link.

Pay special attention to the "How to time" instructions/ procedure,

there's only one correct way!

https://www.2carpros.com/questions/jeep-cj7-1985-jeep-cj7-stalls-when-hot

I hope the pic is legible

We'll fix the other stuff I left hanging when you return.

The Medic

First, thank you so much for such a quick response. Before I start making changes I will add a few more details, add two more pictures and ask a few more questions.

The manifold vacuum source you want me to move the PVC valve vacuum line to is the CTO I think. See pics to confirm. (If it helps below, I will list how the EGR, CTO and Charcoal canister are currently set up by prior owners.) The brake booster is currently connected to this CTO line.

Question 1 - If I connect the PVC line to the CTO metal tube, what do I connect the brake booster vacuum line to?

Question 2 - do I cap off the choke heater port on the carb once I move the PVC line off of it? I think that is what you are referring to in your picture.

Question 3 - one of the prior owners removed all the smog control stuff. The metal tubes coming out of the manifold are simply crimped over. Is this a concern for what I am dealing with? Are these the potential open ports you mentioned above?

EGR Valve - Capped

Coolant Temp Override Switch
CTO Valve Small Port 1 - Capped
CTO Valve Small Port 2 - Capped
CTO Valve Larger Diameter Steel Line Port 3 - Currently connected to the Brake booster

Charcoal Canister - assuming it's only function now is for the fuel tank vent line port 3
Port 1 - Far Left front of motor port - Open
Port 2 - working towards firewall - connected to the windshield washer tank lid (no joke)
Port 3 - Line runs towards fuel tank
Port 4 - closest to firewall Open

Question 4 - Once you confirm the above, I will start making the changes and recheck timing. When I remove the vacuum line from the distributor to check timing, do I cap the port on the distributor and plug the vacuum line going to the carburetor?

Do you have a big port on the carb

Below the throttle plate?

(sucking all of the time-manifold vacuum)

If so, hook the pcv or brake booster to it

Both should have a big port to connect onto.

NO???

How about a big tee to use on the existing line to

connect both onto?

Everything else capped is just fine----just no open ports

sucking outside air!

Of course, get the wiper washer hoses where they go---not on engine vacuum!

Are we making progress?

----The Medic

Making progress. I don't think I have a port on the carb that will work for the brake booster. I have the vacuum port at the base of the carb that the distributor vacuum is hooked to currently. I have a port at the top of the carb which I think is the fuel bowl vent but is currently capped off. It is nowhere near large enough for the brake booster vacuum line.

The last available port would be the choke heater port. What should I do with this port? Cap it?

Back to the brake booster. I will add a T to the PVC line going to the CTO port and connect the brake booster vacuum to the T.

Regarding the charcoal canister, I just want to confirm it can be removed and just add the fuel filter vent in your picture to replace.

Roger on removal

Without the emissions stuff all working, the canister won't operate as intended.

Fuel filter is nothing but a anti-trash/ anti-insect breather

Lets put one on the bowl vent so it can breathe too.

(capping the bowl vent) most likely will pressurize the bowl and when you shut him down after a drive, it will be as if your fuel is boiling out of every crook and cranny of the carb till the bowl is empty from the engine heat.
(seen this happen on BBD carburetors several times)

Possible that this might happen! (about 3 minutes in)

https://www.youtube.com/watch?v=5IGkGBBnDr4

(not mine, but I almost cried anyway!) It can consume the whole Jeep.

So, few inches of fuel line attached to one side of a fuel filter, the other end to the bowl vent port.

in the pic) "to charcoal canister" is the green hose I show up above in the other pic.

If you install headers, the EGR would be eliminated....hence, it is not a necessary item to make the engine run.

I can only suggest things you can do that will work, others might suggest that you put it all back like it was new.

Tee off of the big manifold line (barbed tee from auto store) hook up the booster and PCV.

Tune it the best you can! Return with results.

The Medic

What do I do with the choke heater port on the carb? Do I need to run a line to it from somewhere or can I leave it with nothing attached?

Thanks again for the help and advice. It may be the weekend before I am able to work on it again but will follow up eventually.

Ready to hear something like, "WOW, It's never ran this good!"

The Medic

Hey Medic. I made the suggested vacuum line changes, reset idle, timing and carb (using a vacuum gauge, don't have a rpm meter). Still need to add the vent lines and filters to the carb bowl vent port and fuel tank vent currently running to the charcoal canister.

We had a front coming through with rain so only went for a short run. I hate to jinx things saying this but have to say it really ran well. I need to run it more to confirm. Will let you know if find otherwise.

With this set up, when I use the brakes, the RPMs drop 100 or so. Any concern?

I added a piece of fuel line to the carb choke heater fitting and plugged it. Any concern here?

Thank you so much for your help and advice. I really appreciate it.

The only thing I can see that might help your RPM drop might be if you have another big manifold vacuum port (that sucks all of the time),
and you can put the PCV on one and the booster on the other.

I'm glad you have made a big improvement!

Keep me posted on your progress or if you have other issues that you need assistance with.

----The Medic

Hey Medic. It's been a few weeks. With all the vacuum line changes the jeep was still having issues accelerating at top of 2nd gear and 3rd. Made a decision to replace the fuel tank which was a good one. Alot of trash and old pick-up tube needed replacing. Jeep now runs great up to about 40-45 MPH then acts like it is starving for fuel again. Begins to almost shut off, let off accelerator, it will go a little then want to shut off again. Otherwise runs great as long as around 40 MPH or less. Any other thoughts? It has a 1bbl carter yf carburetor.

Heater thingee on choke!

Normally there is something like a steel brake/ steel fuel Line connected

to it. The other end bends over to the exhaust manifold and runs

down beside it. Hugging/ touching the manifold as much as possible----

this transfers heat into the tube. The inside the choke cover

(in the aluminum) it has a teeny -tiny hole (a little bitty vacuum leak)

constantly sucking air......in a perfect set up---the heated air inside

the steel line. This would warm up the bi-metal spring inside and

aid in the choke to stop choking!

'Round here, the dirt daubers might fill the end of the pipe with their mud,

something to be aware of!

Or you can just leave it open----Or like me install a manual choke.

As a newcomer to manual choke----the worst thing about it is FORGETTING to push it

in FULLY once you are warmed up......usually you figure it out when the JEEP

starts sorta flooding and lacking power!

**********ARE YOU TUNED AS The "Stalls when hot" thread describes to do?

You are not winging it by ear?----using the meters and timing light?

The next thing I'd try----IF YOU ARE TUNING CORRECTLY!

Remove the 1st Add On fuel filter as a test, maybe? it's restricting

Your fuel volume???? Making the carb starve thru lack of refilling

the bowl during a higher demand?

Gotta have everybody working together.....ignoring correct timing....timing at a unknown RPM....ETC, will inevitably factor in evilness!

I'm gonna be your best JEEP buddy now.......Find YOU, in amongst

this stuff in my link........It will be your best buddy too!

Something funny is going on with the link---when you click it,

scoot the screen over to view the right side.

https://oljeep.com/

Once you find your manual, if possible copy it to a thumb drive,

This could disappear at any time!

Let's hear your end now!

-----The Medic