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Old September 22nd, 2012, 04:59 PM   #1
XJsport95
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Exclamation *SOLVED*AMC V8 FSJ Troubles

Hay guys im working on my 83 Cherokee with the AMC 360 with a 2 barrel carb. About 2 weeks ago it started to miss and backfire while i was driving. It felt like it ran out of gas as the pedel went to the floor, but its like there was no motor. At the time it wouldnt go above 45 (40 since the spedo is off a little). So in 2 weeks i have replaced the Plugs, plug wires, cap, rotor, air filter, fuel filter, choke heater, carb spacer, all the carb gaskets, and had the carb rebuilt. Now i put it all back together, and it ran GREAT for about 3 miles. On the way home not so much. It ran exactly the way it did before. I decided to drive it into town (about 6 miles) and on the way in, it straightend out and ran fine. I sat at the beach for a few hours with friends and on the way home again it ran like it did before. Today i started it and it still runs like shit. Im seriously at a loss at to what it might be. The tank is full of premium with a can of SEAFOAM as i though it might be bad gas. It sits there and idols fine, but anytime you start to rev the engine up, it starts to sputter and backfires bad almost as loud as a gunshot. Ive even tried to turn the distributer thinking it might have jumped timing, but when turned in either direction it idols worse. IS there something im overlooking that would make it run bad?

Last edited by XJsport95; October 8th, 2012 at 01:56 PM. Reason: Update on issue
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Old September 22nd, 2012, 06:40 PM   #2
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did you replace the "sock" filter inside the gas tank at the end of the pick-up?
Those have a nasty habit of clogging over time.
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Old September 22nd, 2012, 07:35 PM   #3
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Quote:
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did you replace the "sock" filter inside the gas tank at the end of the pick-up?
Those have a nasty habit of clogging over time.
x=2
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Old September 30th, 2012, 10:45 AM   #4
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Has the timing chain ever been replaced? The factory/stock gear has a plastic coating on it. The plastic becomes brittle and starts to break off causing slack in the chain.
My motor ran good when you first started it up but after it was warmed up, ran like it was out of time. If the motor has never been rebuilt, id replace it anyways and upgrade to a better chain & gear.
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Old October 3rd, 2012, 01:42 PM   #5
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Sounds like fuel delivery problem. Mechanical fuel pump diaphram?
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Old October 3rd, 2012, 04:08 PM   #6
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possibly partially blocked fuel line.
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Old October 3rd, 2012, 09:16 PM   #7
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Sounds like fuel delivery problem. Mechanical fuel pump diaphram?
Agree. I'd look at fuel pump or bad line from tank.
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Old October 3rd, 2012, 09:40 PM   #8
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Once it backfires, the power valve in the carb is a likely culprit. (why would I know this?)

Have you looked at the advance weights in the dizzy?
Swap out the ignition module if you have a spare.

Later,.....Change the distributor to the large diameter cap/rotor (and adapter) from a ford 460 and use the coil from a Ford HEI. HUGE difference in ignition.

Last edited by itselliott; October 3rd, 2012 at 10:29 PM.
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Old October 4th, 2012, 03:24 AM   #9
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With a new distributer and an MSD coil later, Nothing changed. Now im looking at the fuel pump, or possibly the cam, but when i think about each it just dosent make sense. If it was the fuel pump, wouldn't it sputter even at ide? And if it was the cam, say a cam lobe has worn off, it would still sputter at idel. And now with this going on, Ive blown threw 2 sets of headlights. Ive used a ground tester to test that they are getting power, but what would make them both blow at the same time?

Anyways Thanks for all the help and Suggestions thus far guys. Ill let you know if something changes.

-Alex-
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Old October 4th, 2012, 06:18 AM   #10
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Hey man. This could be a bunch of things but I think everyone is on track. Sounds like fuel delivery problem. Yes it could idle great and then drop off when you gave it gas. I would start with replacing the sock filter like suggested. Check all lines for leaks and or any cracking, If you are sucking in air somewhere it could also cause this. If you are runing the mechanical fuel pump still I would replace it also, they are cheap enough.

As for the cam it could also run good at idle but it wouldnt clear up and run good down the road sometimes and run bad other times.

Same thing if it jumped time.

Now with your headlight problem I am wondering if you might have an electrical problem somewhere. Clean up some of the gounds. I would make sure you have a good ground from the motor to the frame.

I am going to be out of town for a couple weeks but when I get back I can come over and give you a hand if you are still having issues.

Good luck.
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Old October 8th, 2012, 12:59 PM   #11
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Quote:
Originally Posted by XJsport95 View Post
With a new distributer and an MSD coil later, Nothing changed. Now im looking at the fuel pump, or possibly the cam, but when i think about each it just dosent make sense. If it was the fuel pump, wouldn't it sputter even at ide? And if it was the cam, say a cam lobe has worn off, it would still sputter at idel. And now with this going on, Ive blown threw 2 sets of headlights. Ive used a ground tester to test that they are getting power, but what would make them both blow at the same time?

Anyways Thanks for all the help and Suggestions thus far guys. Ill let you know if something changes.

-Alex-

Do you have the floor mounted dimmer switch?
They corrode and add high resistance to the circut.
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Old October 8th, 2012, 01:34 PM   #12
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Check the fuel and if that looks good, you might pull the valve cover and look for broken rocker arm bridges. When I first got my Wag it ran differently depending on the day, and when we pulled it for a rebuild, found one brigde was broken and a few others cracked.
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Old October 8th, 2012, 01:55 PM   #13
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Hay guys, First off I would like to say thanks for all the help. All the ideas you guys have given me about the fuel have helped, but not in the way i was hoping as it still ran like crap. I did replace the fuel sock, and inspecetd for line cracks, but found none, which led me to believe that it was a bigger electrical issuse than i thought. I ran into a buddy of mine last night and said that my Jeep was notorious for the Ignition control module for shorting out, so 40 Dollars later, and installed My Jeep runs like a Champ. Took it for a quick test run and it never cut out, and missed like it was.

Thanks For All your Help

-Alex-
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Old October 8th, 2012, 07:44 PM   #14
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Just FYI, many people have had issues with the after market ICM's overheating and cutting out. Basically would run just fine for a while and then overheat and you'd be SOL for a while. I carried a spare in my waggy just in case, i only used it twice, but was worth it lol.

I haven't seen the issue for a little, but i haven't been around them for a few years now.
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Old October 14th, 2012, 05:03 PM   #15
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http://www.junkyardgenius.com/ignition/jeep/HEI01.html
This''ll fix the module problem for good

sorry I didn't think of this sooner..........
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