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CJ Engine Cranks But Dies If I Don't Accelerate

1555 Views 21 Replies 6 Participants Last post by  petersng
Greetings, Jeep friends! I'm having an issue that has been briefed by others in past posts, but I haven't found a solution that works for me. Here are the details:

- Recently bought 1986 CJ7 with 114k miles.
- It ran fine, but there was a massive oil leak at the point where the fuel pump connects to the engine block.
- After doing some research, I removed the fuel pump and replaced the gasket (there actually was no gasket between the pump and engine block).
- That fixed the oil leak and it ran fine right off the bat that same day. However, after the engine heated up, I had some cases of "dieseling" after turning off the ignition. In other words, I turned off the engine and the engine sputtered for a few seconds and shook obnoxiously.
- Yesterday morning, on a cold start, the engine would turn over but then die after a few seconds. After a few minutes of giving it gas when trying to start it, I could finally get the engine to start and idle.
- At another person's suggestion, I closed the choke on the next cold start much later in the day, and she fired right up. However, that trick did nothing for me this morning, and the issue persisted (i.e., having to rev the engine to keep it from dying - after several minutes the engine stayed running and I was able to drive it).
- Idle is now rough - you can hear the rpms going up and down. The engine shakes more than normal
- Tachometer now inexplicably doesn't work. It did work up until this morning.
- Once I get it started, it runs fine. I can turn it off and start it again immediately without issue.
- After a few hours go by, on a cold start the engine will no longer start unless I spend several minutes revving the engine to give it gas.

I'm a neophyte here and bought the jeep to enjoy and learn more about cars. It looks like I'm getting my first real dose of experience through the school of hard knocks!

Any suggestions are welcome! Thanks, and have a great day!
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- Once I get it started, it runs fine. I can turn it off and start it again immediately without issue.
- After a few hours go by, on a cold start the engine will no longer start unless I spend several minutes revving the engine to give it gas.
Start or run?

I'm gonna guess the choke/high idle adjustment is off. You need to pull the air cleaner when the engine is cold and set the choke. It should be completely closed and the high idle engaged. When the engine starts the choke should open about 3/16th of an inch. If not, then the choke pull off is not operating. If the choke is operating properly, then you need to insure the high idle cam is engaged and adjusted.
 

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Discussion Starter · #5 ·
I think you're right regarding the choke. A few things are in play:

1. I'm still having the same issue. On a cold start, it takes 2 minutes or so of revving to get the engine running. Once it runs, there are no issues (subject to 2 below). And once the engine is warm, I can shut it off and start it up without issue. So, I'm really just dealing with a cold start issue . . . for now.

2. As CSP suspected, there are a few leaky hoses in the vacuum system. I haven't had a chance to replace those hoses yet but will do so next week. I think that is affecting the idle (making it choppy and idling at just over 1,000 RPMs).

3. Good call, Jeepdaddy. The choke is wide open on a cold start. I need to figure out how to set the choke and high idle. Any suggestions in that regard would be appreciated. Otherwise, I'm sure there's something on the interwebs/Youtube.

Thank you both for your responses. I love this forum and this Jeep community. I'll get to work and report back. Any other suggestions are, of course, welcome! Have a great weekend!
 

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Pictures are worth a thousand words, show us what you are dealing with!!! :smile2:

The 1984 is cursed by miles of vacuum lines.
 

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Discussion Starter · #7 ·
A few updates (sorry, no pictures yet . . . forgot to take them when I was under the hood):

- Yesterday, I adjusted the choke settings on the cold engine. At full choke, there was probably about a .25" gap between the choke plate and the carb opening. I adjusted the choke to be almost completely closed (so, choke ON). I gave the accelerator two full pumps and turned the key. She fired right up and went into high idle. After she idled for about 30 seconds, I "blipped" the accelerator pedal (just lightly tapped the pedal; I stole this term from another thread), and she settled into her normal idle. I took her for a spin and it was great.

- The engine idles pretty fast. My tachometer (which I think is off a bit), shows it idling at roughly 1,100 RPM. The high idle screw appears to be adjusted correctly, so my guess is the vacuum leaks are leading to the higher RPMs. This week, I plan to replace a number of hoses and we'll see if this makes a difference.

- I had a few cases of dieseling yesterday and again today. I think this is because it's running rich and the vacuum leaks. I'll replace some hoses and see if it gets better.

Thanks again for all of the great thoughts! I'll follow up with pictures.
 

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Vacuum leak is possible

Will surely increase RPMs.

Whether there's a vac leak or just idle speed adjusted higher than it should be---High idle will make one diesel, EVERYTIME!

It will adjust to where it should run correctly---you just have to correct everything so it will

----JEEPFELLER
 

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The dieseling is probably caused by the high idle RPM's.

With the engine cold, the choke plate should be closed.
On a cold December morning, it should lightly snap shut.

Insure the high idle screw is completely disengaged from the cam when the engine is warm. If it isn't, then the cam needs to be adjusted down away from the screw. This usually entails bending the rod a little.

I would do this before looking any further.
 
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Discussion Starter · #10 ·
Thanks, Jeepdaddy. Just so I'm clear, when the engine is warm and the choke plate is fully open/OFF, make sure the high idle screw is not touching the cam. Correct? If it is touching the cam, I assume one adjustment could be to back off the screw?
 

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Discussion Starter · #11 ·
Ok. I tinkered with everything last night. I ended up backing off the high idle screw a bit. As a result, the screw was completely disengaged from the cam when the engine was warm (and the choke was OFF). She still seems to idle higher than she should at about 1,000 RPMs (assuming my tach is correct; but just listening to the engine it sounds like it's idling too high). That said, (a) the car starts right up, which is a major improvement, and (b) the idle, even though fast, is smooth.

I'll replace a few vacuum hoses and see where that gets me. I'm hoping that works. If not, does this group think a nutter bypass is a good route to go down?
 

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A nutter bypass removes the CEC computer from the ignition timing. Hence this is not related to your issues. I suggest you get it right first, this is probably an issue with vacuum leaks or cylinder compressions being uneven, and a carburettor clean and service and reset absolutely vital.

if your current system is not functioning and cannot be easily repaired, you may be in an emissions state that will allow you to remove some of the emissions equipment.

If you do decide to do the Nutter bypass, you will need a new distributor, a 1980/1981 version will have the correct mechanical centrifugal advance. You could alter the current distributor but I understand there are subtle differences internally that make a reman earlier distributor a better solution. They are not expensive.
 

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Discussion Starter · #14 ·
Great feedback, folks. I was out of town last weekend and unable to do work on the CJ, but plan to handle the vacuum-related issues this week. One question - we had a heatwave in Texas over the weekend. I fired up the Jeep on Friday and again last night in hot weather (>80 degrees), and what had been firing pretty easily in chilly weather after making the choke adjustment (and pumping the throttle twice before turning the key) did not fire as easily in the hot weather. It took a minute or two of coaxing to get her to fire up. So another (amateurish) question: Do I need to adjust the choke as the weather changes? In other words, do I go for full choke ON in the cold and open up the choke a bit (so, choke OFF) in warmer weather?

Thanks, everyone!
 

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Discussion Starter · #15 ·
Ok. I took some pics. Apologies for the poor photo quality and the rudimentary labeling.

Some notes associated with the numbering:

1 - This is uncapped/unhosed and there's definitely some vacuum there. I can hear air being sucked in through this port. When I put my finger over it to plug it, (a) I feel suction and (b) the idling smooths out. Based on internet research, it looks like this should go to the EGR system? I assume this can and should be capped. Correct?

2 - This appears to run from the Bowl vent, correct? As you can see, the hose has been taped and their is damage to it. I assume the hose needs to be replaced, but is this just air flow and not vacuum? If that's the case, this would not impacting idling, correct?

3 - Is this the break booster line? The hose is taped up and has holes. I assume this needs to be fixed and will replace the hose. But, my question is, is this a hose/line that would create an idling issue?

Thanks!
 

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#1 and #3 are your major issues! I'm actually surprised it idled at all. Not knowing how you have your vacuum lines run on your rig - looks pretty-much stock from the images - but that's an assumption! To start, place a cap of #1 and replace the rubber portion of the brake booster hose - should be able to remove the rubber hose from the metal portion, once replaced, use a clamp to secure it, and double check the plastic fitting in the booster for snug fit: your goal is zero leaks.

Leaks at both of these definitely will cause major idling problems. Once you do that, then you can begin to fine tune how your engine is running-

Best,
Hoover
 
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Discussion Starter · #18 ·
I capped port #1, and noticed immediate improvement. RPMs didn't drop too much, but the idle smoothed out significantly and the ride is a lot quieter without all of the chugging.

I'll replace the hoses for #2 and #3 soon.
 

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That's a great positive step. Now that you are addressing your major vacuum leaks, there still might be other leaks that can negatively affect it's performance, and will need to check thoroughly. If you are seriously inclined to learn more about your engine, you'll need to get familiar with the different systems in place on your stock configuration. This website does a great job of describing all the emissions systems that your jeep is currently running. Emissions doesn't necessarily mean bad, but there are some systems that are more beneficial than others, and some can be altered easily unless you live in an emissions-required state for road operation (since you don't have a location listed, can't speak to that). Check it out for a great overview of how those systems work. From your images, the CTO valve is missing a connection. I suspect that the port you capped (#1) may have been connected there, but not certain. That website will tell you what the CTO valve is, and moreover, what it does. As well as the EGR, ICM, etc. It's worthwhile to spend some time looking it over. And, when you can't find answers there, this forum has a bunch of knowledgeable folks who can get you pointed in the right direction.

Seeing a stock jeep like yours is becoming a rare thing these days. I'd be happy to have one like that!

Best,
Hoover
 

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Discussion Starter · #20 ·
Postscript: I replaced a number of leaky hoses and the engine runs and sounds so much better. The engine doesn't shake/vibrate nearly as much, and it's about as quiet as a Tesla! Ok, not that quiet, but you get the picture.

So, that problem seems to be buttoned up. And, of course, another problem arose in the form of a tachometer that no longer wants to work. Something new to research. It's always something!

Thanks, everyone for the help here. I appreciate it!
 
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