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Unread 10-30-2009, 12:47 PM   #1
Aduffy32
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1998 TJ Wrangler 
 
Join Date: Aug 2009
Location: Tucson, Arizona
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Awful sound when turning jeep off

Whenever i turn my cj off after i have been exerting it a little, it almost sounds like its trying to start back up again. After about 4 seconds it sounds like pressure gets released then it stops. Its sort of scary. Any ideas? thanks

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Unread 10-30-2009, 02:06 PM   #2
Fatman
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Quote:
Originally Posted by Aduffy32 View Post
Whenever i turn my cj off after i have been exerting it a little, it almost sounds like its trying to start back up again. After about 4 seconds it sounds like pressure gets released then it stops. Its sort of scary. Any ideas? thanks
Based upon the amount on information you have provided us about your Jeep's setup ..... motor, trany, modifications ?

No idea!


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Unread 10-30-2009, 02:13 PM   #3
Aduffy32
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The motor has been rebuilt by performance powertrain about 5,000 miles ago , and I believe I have a stock 5 spd transmission. I also have a MSD ignition box, and an upgraded clifford carb, and an electric fuel pump. Sory about the lack of information before
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Unread 10-30-2009, 02:28 PM   #4
Fatman
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Might want to check for air leaks around the manifold.
Also, with electric fuel pumps, it's nice to run a switch into the relay so you can shut off fuel before you kill the ignition. I'd also want a kill switch on the MSD, but that's more of a security thing with me.
Still not sure what motor your running, but some ideas for you to chase.
Al least you're not dieseling.
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Unread 10-30-2009, 02:42 PM   #5
Scuter83
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I had something similar in my stock '74 CJ5 with the 258 in it. I lowered my idle speed and re-set the timing. I also added in the vacuum advance. That has seemed to fix my problems.

To me it does sound like you are dieseling. To me it sounds like you are firing little by little still after you shut the key off and then finally it dies and backfires a little through the carb. Next time you shut it off, try to pull the choke as you shut it off and see if it doesn't do it. That used to work for me some, not really a fix, but then I knew it was something with the carb. I attributed it to my high idle and incorrect timing causing fuel to get sucked out of the carb and hot spots in the cylinder to fire the fuel off.

Scott
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Unread 10-30-2009, 02:43 PM   #6
CSP
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Sounds like run-on to me. It's either a problem with timing that's too far advanced or hot spots in the cylinders.
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Unread 10-30-2009, 02:45 PM   #7
BioTex
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Fatman,
Why do you say he's not dieseling? That is what it sounds like to me. Also known as run-on. If I have my timing off, it will diesel. Sounds just like it is trying to stay running. The hotter the engine, the more it does it. I tweaked my timing, and it completely cured it. Engine was a 258, and recently rebuild just like OP's.

Higher octane gas will help alot, especially with a lot of advance.
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Unread 10-30-2009, 02:49 PM   #8
Jeepican
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Maybe your hampsters have bad gas????
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Unread 10-30-2009, 02:57 PM   #9
Fatman
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Dieseling sounds more like dead chug or run-on. Much like you see when you have an automatic trans.
I interpreted his "Awful sound" as post ignition detonation. Air leak and un-burnt fuel.
Agree timing advance is playing a role here.
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Unread 10-30-2009, 03:26 PM   #10
Mike Romain
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I would want some more details of the noise and 'run on' maybe before guessing.
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