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Discussion Starter · #1 ·
So I am relatively new with carbs and CJs so I need some help with my vacuum lines. I recently put a new cam in the 304 because the old one was flattened and I have had problems keeping it running. I finally got it to idle at about 1100 rpm, but it would stop past that. For this I had every port on the carb plugged and the choke plate was closed with no air cleaner. Now I am trying to keep the choke fully open with an air cleaner and it won’t idle anymore. I am trying to determine what vacuum lines I need for this engine to get it to run properly. I have no egr valve, break booster or a vacuum advance on my distributor. I tried to connect a vacuum to the intake manifold to some of the ports, shown below, and have tried a couple of different combinations but nothing is making it idle, of course I have played around with the mix screws and idle screw, it still won’t idle. Can anyone help?

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Have your searched for a vacuum diagram? I may have one but I'll have to look around. Think I pulled it off here years ago.

Remember also you should compare 77-80 304 diagrams as they stopped offering them in 81 and each year got more smog stuff added to it so your 85 is definitely a swap and you won't find a V8 anything for it going by the year.

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I would start with getting power to the electric choke to make sure that it is opening correctly, 2nd I would throw that piece of foam that tries to make you think that it is an air cleaner as far as you can and either put a stock air cleaner on or at least an open element air cleaner with a paper filter
 

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If you are idling at 1100 RPM with all vacuum ports blocked, you have a vacuum leak somewhere. I also would not try looking at a factory vacuum diagram because what you have is very not factory.
1) Plug EVERY SINGLE HOLE/PORT in your carb and intake manifold. EVERY ONE OF THEM. Remove ALL the vacuum lines. EVERY ONE OF THEM. Set your timing to 10-15 degrees (NO Vacuum input, at idle). Then tune your carb to idle correctly. My 401 with a mild cam would idle at 700RPM all day like this. If your 304 does not, you need to start looking for where your vacuum leak is. Check under your carb. I also see you have an adapter plate. check there. If those both check out, you may have set your intake down cocked and have a leak in the valley. If you need help finding a vacuum leak, post up.
2) Once you have it idling well, hook your vacuum advance to you distributor up to manifold vacuum and set timing to a total of 34 degrees at 3500RPM (if you need help with this post up)
3) These are the Must have connections for your truck. I see you do not have a brake booster so you don't "need" that. Do you have an PCV valve? if so, connec that to the big port on the back of the carb near the base plate.
4) Do you have a carbon can?
 
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Discussion Starter · #5 ·
If you are idling at 1100 RPM with all vacuum ports blocked, you have a vacuum leak somewhere. I also would not try looking at a factory vacuum diagram because what you have is very not factory.
1) Plug EVERY SINGLE HOLE/PORT in your carb and intake manifold. EVERY ONE OF THEM. Remove ALL the vacuum lines. EVERY ONE OF THEM. Set your timing to 10-15 degrees (NO Vacuum input, at idle). Then tune your carb to idle correctly. My 401 with a mild cam would idle at 700RPM all day like this. If your 304 does not, you need to start looking for where your vacuum leak is. Check under your carb. I also see you have an adapter plate. check there. If those both check out, you may have set your intake down cocked and have a leak in the valley. If you need help finding a vacuum leak, post up.
2) Once you have it idling well, hook your vacuum advance to you distributor up to manifold vacuum and set timing to a total of 34 degrees at 3500RPM (if you need help with this post up)
3) These are the Must have connections for your truck. I see you do not have a brake booster so you don't "need" that. Do you have an PCV valve? if so, connec that to the big port on the back of the carb near the base plate.
4) Do you have a carbon can?
I will start with trying to get it to idle with everything plugged. One thing I’ve noticed is that I can’t get it to idle with everything plugged with the choke fully open. It will only idle if the choke is closed mostly, like1/8th in open. There is a gas leak on the adapter plate so that’s where the vacuum leaks must be. My distributor does not have a vacuum advance for some reason. Do I need to get one with a vacuum advance? I do not think I have a carbon can. Where can I find that? And where can I find the pcv valve. I think I have one but I’m not too sure.
 

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I also notice in your pictures, it looked like you have your engine coolant temp sensor in a vacuum port (that brass piece with the threaded post in it is the temp sensor). See this pic:
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The green items you have are good. In the far left yellow circle there used to be a vacuum switch (called a CTO). If you have no vacuum advance, plug that for now. the other yellow circle is the port some of us used for a brake booster. you can plug that for now, too.

Post a pic of your dizzy. I assume you have an HEI and that is why no vacuum can. I would think you "should" have a can but that depends on a few things. Lets see if we can get it to idle well before we figure that out.

Oh, and like fourtrail said, swap that air filter thingy out. it's terrible at both filtering air and flowing air.
 
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Oh, I see your distributor now. I see you have a Mallory. I do not know much about those. I, personally, really like the Duraspark distributors and they are pretty cheap. Your ignition is working right now, don't mess with it.

Honestly with that set up, I do not see ANY vacuum lines you would need.
 
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Discussion Starter · #8 ·
Oh, I see your distributor now. I see you have a Mallory. I do not know much about those. I, personally, really like the Duraspark distributors and they are pretty cheap. Your ignition is working right now, don't mess with it.

Honestly with that set up, I do not see ANY vacuum lines you would need.
From your diagram I understand a lot more now. Thank you. It looks like my pcv valve is blocked off. Should I get a pcv or just leave it as is?
 

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I wouldn't yet but in the in the long run, yes. First you want it to run well without it, then you can plug it in later.
 
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Following :)
 
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Discussion Starter · #11 ·
Update:
So far I have everything plugged from the diagram and on the carb. Choke is fully open and I can not get it to run with no matter how many different combinations I try with the throttle and mix screws. It’ll start then die in about 5-10 seconds. I got new gaskets for my carb and adapter plate. Now there is no leak. What do I need to start checking to see whats causing her not to idle?
 

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1) when it does start, for those 5-10 seconds, can you play with the throttle and keep it running or does it still die even if you feather the throttle?
2) Where is your timing right now? since it will not stay running long enough to get the timing correct, at least get it at close to TDC as you can eyeball it. if you need help with that, let us know.
3) are you running a mechanical or electric fuel pump?
 

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Discussion Starter · #13 ·
1) when it does start, for those 5-10 seconds, can you play with the throttle and keep it running or does it still die even if you feather the throttle?
2) Where is your timing right now? since it will not stay running long enough to get the timing correct, at least get it at close to TDC as you can eyeball it. if you need help with that, let us know.
3) are you running a mechanical or electric fuel pump?
1) when it starts I can keep it alive by playing with the throttle and 2) my timing last time I checked when it idled with the choke closed was about 24 Btdc at 1100 rpm. I adjusted it a little more so it should be a little lower and 3) I have a mechanical fuel pump. I know that works good because I had it off then pumped it and it went all over me haha.
 

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If you look down the carb, with the air filter off, and you open the throttle, do you see fuel spray in?
It still sounds like a vacuum leak to me. Try getting it to run and remove the oil fill cap and put your hand over the fill tube. See if there is a little vacuum there (there should not be). I assume the throttle stop screw is not backed out all the way? If it is, try giving it a few turns and verify it is touching the throttle arm and holding it partly open. Also, have someone crank the engine over a few times and verify there is no fuel spilling into the engine.
 
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It's not going to run well at first because it is stone cold and the choke is not set up yet. You may need to feather the throttle to get it to warm up and hopefully then it will idle. Since you do not have a vacuum advance, I would think you would want your timing at idle to be 12-18 degrees (maybe 20). I never had a 304 so I am not sure what they like. My 401 really liked 20 degrees at hot idle (700RPM).
 
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Discussion Starter · #16 ·
If you look down the carb, with the air filter off, and you open the throttle, do you see fuel spray in?
It still sounds like a vacuum leak to me. Try getting it to run and remove the oil fill cap and put your hand over the fill tube. See if there is a little vacuum there (there should not be). I assume the throttle stop screw is not backed out all the way? If it is, try giving it a few turns and verify it is touching the throttle arm and holding it partly open. Also, have someone crank the engine over a few times and verify there is no fuel spilling into the engine.
yes fuel sprays in when I open the throttle and I’ll try that right now. The throttle screw is touching the plate holding it open
 

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You need to cap off the vacuum ports on the carb and the one on the intake, it looks like you have the two bigger ones on the carb t'd into the vacuum port on the manifold. The port on the front next to the driver side mixture screw IIRC is ported, not manifold vacuum and that is likely where your vacuum 'leak' is at.
 

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Discussion Starter · #18 ·
If you look down the carb, with the air filter off, and you open the throttle, do you see fuel spray in?
It still sounds like a vacuum leak to me. Try getting it to run and remove the oil fill cap and put your hand over the fill tube. See if there is a little vacuum there (there should not be). I assume the throttle stop screw is not backed out all the way? If it is, try giving it a few turns and verify it is touching the throttle arm and holding it partly open. Also, have someone crank the engine over a few times and verify there is no fuel spilling into the engine.
Also there is no vacuum on the oil fill when running
 

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Discussion Starter · #19 ·
You need to cap off the vacuum ports on the carb and the one on the intake, it looks like you have the two bigger ones on the carb t'd into the vacuum port on the manifold. The port on the front next to the driver side mixture screw IIRC is ported, not manifold vacuum and that is likely where your vacuum 'leak' is at.
I have everything capped off now on the carb and the intake manifold so there is no vacuum running right now
 

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I feel like you had a few bad vacuum leaks but your carb was so rich, it would run at 1100 RPM. The reason I ask about fuel dripping in when cranking is if the needle valve is stuck open it will drip fuel into the engine and kill it.

Check these holes and see if they are pulling vacuum.
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Also, when you pulled the adapter to replace the gaskets, did you check to make sure the adapter is not bent? If the bolts are over torqued it will pull them down and make it impossible to seal directly under the carb.
 
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