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Unread 01-09-2015, 12:53 PM   #1
HydraulicKnight
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CJ7 258 Running Issues!!! Please Help!!

I have had a 1986 cj7 for about 4 months now and still cannot get it to run right. Here is the story: Jeep came with the factory carter. It would start and idle pretty good, but would die when you drove it a few feet (longer on flat ground). I thought the carb was the issue so I installed an MC2100 that I rebuild. Took me a while to get everything right (pulled the tank and cleaned out bad gas), but I finally got it starting and running again. Now I am having the same problems!!!

It will start and idle and rev all day, but when I drive it will die. I can get going down the street, it will do good for a few hundred feet, then it will start cutting in and out and eventually die. If i feather the throttle I can get it back home. After I get parked again it will start and idle for a little while and die again. If I let it get cool again it will repeat the process: start and idle and rev great all day long, but cut out and die when I try to drive it.

My question is could this be an ignition problem??? I have done everything possible to the carb, rebuilt 1.08 venturi with 47 jets and thermal choke). No vac leaks.

Please Help!! I have to get this thing going.

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Unread 01-09-2015, 01:08 PM   #2
rickscj7boom
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when mine did that it was a vac leak from the brake booster. how is the fuel flow is fuel filter positioned right? post up some pics, we love pics.. good luck keep us posted!!
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Unread 01-09-2015, 01:34 PM   #3
HydraulicKnight
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No brake booster. I replace the fuel filter with a factory style one. I blew out all the fuel lines when I cleaned the tank. Here is a couple pics. I'm running the PCV and Vac advance only right now. Everything else on the carb and the canister is plugged.
img_2023.jpg   img_2026.jpg   img_2024.jpg   img_2027.jpg  
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Unread 01-09-2015, 02:01 PM   #4
dg6772
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Sound like a vac leak to me too. That said, I had a similar problem with a camaro years ago. Would idle fine, rev OK also, but not drive very well. After giving up on that sbc 327 figuring something enternal was bad I swapped in a very healthy sbc 350. Upon starting I blew the muffler right off the pipe. Turns out it had broken inside and was restricting exhaust flow. I later replaced the 350 with the original 327 and all was good.

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Unread 01-09-2015, 02:12 PM   #5
Matt1981CJ7
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First thing I'd do is get that fuel filter away from the valve cover. I't's probably not the problem, but that's not a safe location for it.

Is that as far as the choke plates close when you set the choke? Or is that the position they are in when you shut the warm engine off? Also, check for any goo oozing out the back side of the ignition control module.

Lastly, I see you've capped off the vapor canister except for the tank vent. If the filter in the bottom of the canister is caked with mud, your tank may not be vented. Have you taken a run with the gas cap off?

Matt
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Unread 01-09-2015, 04:07 PM   #6
HydraulicKnight
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Thanks for the feedback.
The muffler was replaced with some long glass packs (not too loud). It seems to be getting good exhaust flow.

I agree with moving the fuel filter. I'm going to do some trimming/fitting with all of the vac, fuel, and coolant lines when I get it going.

The choke plate does close a little more than that. I think it is set at 1/16" - 3/32" at cold start. It open more when the engine is warmer.

I will check the gas vent. Earlier when I pulled it back in the garage it did have kind of a surging/variable idle that may point to a vac leak. It just seems weird that it only shows itself when trying to drive the vehicle. upon cold start it idles and revs really well. Much better than the carter did.

Ill test the fuel vent and report back. Thank you for the help.
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Unread 01-09-2015, 04:34 PM   #7
Matt1981CJ7
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I'd focus on the choke for a moment.

When the engine is cold, the choke plates should close fully. Then, when you first fire it up, the choke plate should open slightly. On most carb they will "pulloff" about 3/16". As the engine warms the choke plate should gradually open until they are almost vertical.

Matt
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Unread 01-09-2015, 07:25 PM   #8
HydraulicKnight
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I have definitely battled the choke and am not sure if it is setup right. I have it set to where I pump the pedal and it will fire up and run at about 1K RPM. I let it idle at this for a while then pump it again to step it down to around 700-800 RPM (don't have a tach). The choke will SLOWLY open, but I have the thermal intake port plugged because I causes a vac leak if I leave it open. I have a manual choke kit that I'm tempted to install. I'm not sure if manual is the more reliable way to go, but I am thinking it may be my best option since I'm struggling with setting up the auto choke. I have also battled the fast idle a bit as well , but it seems to work well enough. I do not have the choke pull off solenoid.
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Unread 01-09-2015, 07:26 PM   #9
HydraulicKnight
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My assumption is if it idles and revs well, it should also run well, but I'm sure there are many other variables that I am missing.
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Unread 01-09-2015, 08:56 PM   #10
BagusJeep
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Have you Nuttered the ignition? You do not have the BBD carb so there is no point in the emissions system being left in.

As you are probably aware the CEC computer alters the ignition timing based on inputs from variou sensors and switches as well as the carb. If you have the same emissions distributor it was set up with limited mechanical advance and relied on the CEC computer to do the rest, which it did poorly.

Have you checked that you have reliable fuel flow? By this I mean do you have any means of checking, such as a clear piece of fuel line etc that you are getting fuel in there when it is running and not a fuel and air mixture.
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Unread 01-18-2015, 04:33 PM   #11
HydraulicKnight
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Just got back from some travel. its around 60 degrees so I messed with the Jeep today. I pulled the gas cap to check the tank vent and I saw no difference. I have not checked the fuel flow, but I did have a clear filter on there and it stayed about 80% full. What would cause air to get in the lines?
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Unread 01-19-2015, 01:09 PM   #12
HydraulicKnight
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I nuttered the Jeep today and still have the same problems. I also unhooked the exhaust to check the cat. No difference. It really feels like it is flooding out. Sometimes after it dies it wont start unless I let it set for a while I'm at a loss here and really need some help here.
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Unread 01-19-2015, 10:24 PM   #13
rickscj7boom
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Does it have electric or mechanical fuel pump?
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Unread 01-20-2015, 07:19 AM   #14
Mike Romain
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Quote:
Originally Posted by HydraulicKnight View Post
Just got back from some travel. its around 60 degrees so I messed with the Jeep today. I pulled the gas cap to check the tank vent and I saw no difference. I have not checked the fuel flow, but I did have a clear filter on there and it stayed about 80% full. What would cause air to get in the lines?
Air gets in from pinhole leaks caused from the ethanol in modern gas. It dries out the rubber lines so they crack and rots out the steel lines from all the water it carries.
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Unread 01-20-2015, 07:33 AM   #15
HydraulicKnight
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It is the stock mechanical pump. I have checked the pump by taking the carb inlet line off and cranking gas into a cup. Seemed to be pumping fine. I will check the flexible gas lines at the tank for cracks, but they appeared to be in good shape when I pulled the tank. I'm going to do a tfi ignition upgrade along with new plugs to eliminate the distributor, plugs and wires as the culprit.
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