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Unread 07-25-2013, 09:38 PM   #1
Jdtench
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1978 CJ5 
 
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Location: Clermont, GA
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CJ5 258 sputtering 3/4+ throttle

Hey, I'm new to the forum and am a new owner of a 1978 CJ5 with the I6 and 4 speed transmission. My grandfather fully restored this thing (he claims $25k invested) 10 years ago and placed it in a garage of an old house of his. The roof collapsed and it has been getting rained on for I don't know how long. I pulled it out a couple of weeks ago and have been working on it. We have struck a deal and now I'm the owner. It is running and it didn't take too much to get it to run (new starter, new battery, freed up some linkages) and it ran on 10+ year old gas. I have driven it probably 200 miles since I've been working on it and it runs great. However, it has a sputter when you really get on it. I found a small pinhole in the fuel line between the fuel pump and fuel filter, fixed that and it has helped some, but it still has that sputter. It is difficult to get up to speed acting this way. I know it can be a variety of issues and I have scoured this forum looking for similar cases, but none of them are really like the issues I'm having. The jeep idles great and runs great up until you give it 3/4 throttle. From there to WOT it has a sputter. It still accelerates (slowly on level ground) but it is sputtering out the exhaust. It almost seems like it is starving for fuel, but I replaced the fuel filter yesterday. Has anyone experienced this kind of behavior before? Oh, I forgot to mention, that after I fixed the pinhole in the fuel line, it took it 30 minutes to start acting like this, the first 30 minutes were perfect, then it started sputtering. It's almost like it waited until it was nice and hot to start acting up. Anyone have experience with this problem before? Any help is appreciated!


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Unread 07-25-2013, 10:00 PM   #2
Trapshooter
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First.....Welcome to the Jeep Forum!! Tons of stuff here for your CJ5. Great looking rig!!

The issue you are describing could be caused by any number of things. A distributor that is not advancing properly, old spark plugs or partially fouled, excessive exhaust system back pressure, gummed up carb, debris in the fuel tank that is covering the fuel outlet, etc.

You are going to need to continue to eliminate items one by one. The biggest issue you have is a rig that has not been operated in ten years.

Good Luck..............
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Unread 07-25-2013, 10:45 PM   #3
dison001
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1976 CJ5 
 
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Nice ride! Im far from an expert, but it sounds like a simple vacuum leak. Possibly as simple as the hose for your vacuum advance being cracked.
Hope its something simple and obvious. I hope mine looks that good soon.
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Unread 07-26-2013, 03:07 PM   #4
Jdtench
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Ok, the sputtering has all but stopped. I looked at the vacuum advance and the distributor and cleaned all of it really well. I don't think it was advancing enough (not enough movement from gunk being in there). Now, it has a new symptom. I will be driving along fine and all of a sudden it'll bog down. If I let off the throttle it'll return to normal for a brief second then bog down again. If I keep the throttle so it stays bogged down, it'll backfire. It almost seems like it is not getting enough fuel. I guess I need to really inspect the fuel system (carburetor and fuel tank) It runs so well otherwise.
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Unread 07-26-2013, 03:55 PM   #5
Jack718
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I had a similar probably and it drove me crazy trying to figure it out and it ended up being a bad fuel pump.
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Unread 07-26-2013, 04:00 PM   #6
LumpyGrits
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Points ign?
What the rpm when it stumbles?
3/4 pedal, under load or cruise'n.
Can you 'sneak' up on it, or is it every time?
LG
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Unread 07-26-2013, 04:19 PM   #7
WindKnot
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He should have the Motorcraft Electronic Ignition if it's stock.
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Unread 07-26-2013, 04:37 PM   #8
jdarg
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I'd rebuild a carb thats been sitting that long. Odds are the pump diaphragm is bad. If you can accelerate but only if you do it very slowly and gradually (as opposed to mashing the pedal half way down, etc.) that is your must likely culprit of the poor acceleration.
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Unread 07-26-2013, 07:14 PM   #9
LumpyGrits
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SWAG+ gummed up gas mixed with water.
Replace fuel and fuel filter.
LG
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Unread 07-26-2013, 07:29 PM   #10
86cj74.2L
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The more you flogged it the more dirt got sucked into the main jets possibly.

Do you have a two barrel or a 1 barrel carb?

Like mentioned earlier sitting that long its a good idea to take everything apart, making sure nothing is growing in the fuel bowl.
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Unread 07-26-2013, 09:38 PM   #11
Jdtench
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Ok, I had patched a pinhole in the fuel line going from the fuel pump to the fuel filter, but never could quite get it to quit leaking. So, I ordered a replacement and got it in the mail today. Installed it and it solved the problem! I do plan on going through the whole system soon, but glad to know that that issue has been resolved. Thank you guys for your help, this place is great! I should probably mention for future reference that I did pull the distributor cap and rotated the center just a little and heard a pop. Sounded like something got dislodged and then allowed it to advance further. This got rid of the sputtering.
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Unread 07-26-2013, 10:14 PM   #12
BagusJeep
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You may be sucking air as the hoses above the fuel tank rot and split. They start allowing air in which gets worse over time and you will hear the engine spluttering flat out or going uphill, the pump is sucking air in and the level in the float bowl in the carb starts to fall.

If you let the engine idle for a minute and then it is fine for 20-30 seconds before it starts splutterring it is almost certainly the level in the float bowl sinking.

As it has been sitting you may find some benefit in dropping the tank, cleaning it out and checking all the hoses at the back. The fuel pump diaphragm could also have rotted but the pumps are cheap.
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Unread 07-27-2013, 12:29 AM   #13
Jeep-N-0311
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That's a pretty little jeep. It's great that you got it (mostly) running good.
Just a thought. Now might be the time to go through the fuel, ignition, vacuum, brake line and lube systems (all soft and fluid systems) and check, clean, replace as needed, or as a precaution. Then you can monitor all systems, including the hard mechanicals. Like has been said before in this thread, 10 years is a long time to sit, and petrochemicals, their hoses, seals and filters don't all really sit around to well (once they're out of the box and out of environmentally-controlled warehouses.) Some of the old electricals could be getting up in corrosion as well. BTW - as other(s) have mentioned - there's improvements (i.e. - Nutter) here on the forum that usually work a lot better than the old systems that the OEM installed (and are a LOT more "KISS" than the OEM systems as well - important when PM'ing).

Good luck
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