Engine will not stay running?

Tiny
WHITEWULLFF
  • MEMBER
  • 1976 JEEP CJ7
  • 5.0L
  • V8
  • 4WD
  • MANUAL
  • 120,000 MILES
Hello, a couple months back I had several knowledgeable folks helping with my vehicle, 304. I have finally got it running and rebuilt the carburetor, (motor craft 2-barrel 2100). New points, rotor, and cap. It runs if I keep feeding it gas and eventually on its own for a little bit. While it is running it’s surging and missing. Slightly turning the cap does nothing. Unplugging the booster hose from the back of the carburetor revs the motor to a high idle no longer surging. Smoke fuel smell and smoke coming out of carburetor. And now a slapping not knocking doing from bottom of motor. I really need some help here. Thanks
Sunday, September 11th, 2022 AT 7:55 PM

19 Replies

Tiny
KEN L
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No problem, can you please shoot a quick video with your phone so I can hear the noise in the engine? That way I can tell for sure what's going on. You can upload it here with your response. Also, if you unplug the booster and the engine runs better the booster is no good.
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Monday, September 12th, 2022 AT 11:47 AM
Tiny
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Well, it started for about two seconds and now I can’t get it to start as you’ll see. I’ll send a vid when I get it to start. Thank you
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Wednesday, September 14th, 2022 AT 12:24 PM
Tiny
KEN L
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It looks like the battery is weak or the battery cables are bad, also make sure there is a good ground from the battery to the engine and then to the frame. Thanks for the video, it really helps us get to the problem.
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Thursday, September 15th, 2022 AT 8:55 AM
Tiny
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Would that make it run bad or shut off? I have a mechanic friend that said he would take a look. When I initially dropped it with him, he saw the smoke/steam coming out of the oil spill pipe. It happens immediately as the motor starts. And continues for a min after it shuts off. He’s very concerned about this. I replaced the valve stem seals and head gasket. I guess it possibly could be the rings are bad. Oil dipstick shows no coolant and radiator coolant shows no oil. No smoke from tail pipe although you can smell oil and gas. One other thing. Once in a while, when idling, coolant began to boil out. Knowing the motor wasn’t even warm yet, I popped the radiator cap to relieve pressure. The coolant did boil out but was cold.
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Saturday, September 17th, 2022 AT 2:29 AM
Tiny
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Oil fill spout is what I meant.
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Saturday, September 17th, 2022 AT 2:30 AM
Tiny
KEN L
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It sounds like you need a new thermostat. Can you take a video of the tailpipe so I can see what's going on?
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Monday, September 19th, 2022 AT 3:19 PM
Tiny
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Yes sir. I’ll drive over there tomorrow and get a video. I did replace the thermostat, however that doesn’t mean the new one isn’t bad as well. Thank you for staying with me on this, I really do appreciate your knowledge.
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Wednesday, September 21st, 2022 AT 4:11 PM
Tiny
KEN L
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No problem, that is what we are here for.
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Thursday, September 22nd, 2022 AT 12:09 PM
Tiny
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So far, the mechanic says I need to start with a new carburetor. I just rebuilt this one but maybe I messed it up. So, I’m going to tow it home and try to find a different carburetor. Times are tough right now so I may have to put this conversation on hold until I can find a way to buy a carburetor. I still have a little time before my daughter's 16th in Jan. But this is her present so hopefully not too many more issues. Well, I do appreciate your help. It’s nice knowing I got someone there to kind of guide me in the right direction. I’ll be back once I’m able to afford a carburetor. Talk to you soon.
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Friday, September 23rd, 2022 AT 1:51 PM
Tiny
KEN L
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Happy birthday to your daughter and let me know how it goes. We are here when you need us.
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Saturday, September 24th, 2022 AT 10:09 AM
Tiny
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Thank you.
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Monday, September 26th, 2022 AT 6:04 AM
Tiny
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Hello Ken,

I got my cj7 back from the mechanic and wasn’t able to do anything with it besides suggest I get a new carb. I took the motorcraft 2100 off and found the two brass tubes on the venturi, I believe they are called dwell tubes. They are both cracked. Tried to solder and braze but no luck so I put chem resistant jb weld on just to see if it ran better. Here is a video from today.
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Sunday, October 23rd, 2022 AT 5:59 PM
Tiny
KEN L
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The video was good, it looks like you have a vacuum leak or the power valve diaphragm that is bad in the bottom of the carburetor toward the front, if you remove the four screws from the cover and you see gas the valve is bad, this is a very common problem and a cheap fix. Check for vacuum leaks when cold only.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go over this guide and report back.
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Monday, October 24th, 2022 AT 12:15 PM
Tiny
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Okay. I must be missing something. And I know there are only so many things that will cause certain symptoms. But I just keep going around in circles. I just rebuilt the carburetor and power valve was the main component. It’s possible it is bad, or I installed wrong. However, I was having this issue before the rebuilt kit. Now vacuum leak I myself and two other mechanics have looked at it. One did find a vacuum leak and the engine ran great till he left. Lol then went right back to stalling. I’ll open up carburetor and see if there is fuel in the valve.
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Thursday, October 27th, 2022 AT 4:27 PM
Tiny
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One thing I just noticed. I pumped some fuel out of the Jeep through the line going into the carburetor. And it’s yellow. In the pic oh can see the difference. The other bottle has gas I just filled up from gas can at station. What would cause the fuel to turn yellow? It’s not old gas and does smell like oil. I'm not sure how I would get oil in gas. I know the other way is possible but.
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Thursday, October 27th, 2022 AT 4:40 PM
Tiny
KEN L
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Yellow fuel is normal, does this engine have an EGR valve is so please remove it and check it for leaks.

This video will help:

https://youtu.be/DqUCbbKdWf4

Please go over this guide and report back.
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Saturday, October 29th, 2022 AT 2:23 PM
Tiny
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No, it’s been deleted. But I’ll check out the video. I took the carburetor in to carburetor pros to have rebuilt. Going to be more expensive than a new one online.
However, after all my research on the correct carburetor to run in 304 and sifting through all the forums and opinions I’ve come to the conclusion that the right one is the one that works for you. 1.08 venturi is not enough CFM for this motor and starving for air which is why it ran better when I unplugged the booster. The 1.14 is in a carburetor that won’t fit so I’m having it bored out to 1.21.
You were correct, there was fuel in the power valve. The kit included a new superpower valve but didn’t include the bigger plate cap to fit over it, so I put the old back on. Anyways, we’ll try this and go from there.
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Saturday, October 29th, 2022 AT 9:54 PM
Tiny
KEN L
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If it runs better with the brake booster disconnected you may have a bad booster which is causing the vacuum leak.
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Monday, October 31st, 2022 AT 11:33 AM
Tiny
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Okay, I remember you suggesting that so it’s on the list to check.
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Wednesday, November 2nd, 2022 AT 6:47 PM

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