79 cj7 304v8 stalls after warm; won't restart till cool - JeepForum.com

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post #1 of 9 Old 11-04-2010, 06:12 PM Thread Starter
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1979 CJ7 
Join Date: May 2010
Location: Chattanooga
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79 cj7 304v8 stalls after warm; won't restart till cool

guys, so sorry; have searched all related topics in forum and cant find the answer i need...79 cj7 with the 304, stock. It starts right up, idles high for a minute, then when warm idles down lower (after i pump the pedal). I can drive it around town for a short period (~15 minutes) and then when it comes to rest at a stop sign/light and idles it will die. Will not restart for a period of time (i assume when its cooled off?) Can drive it on the highway indefinitely with no hiccups, hesitation, etc. then when I exit, same thing applies. Have replaced the ignition module, fuel filter (2x- but clean 1st one), new battery, new fuel pump, new wires, plugs, and has MSD ign. coil and stock (?) motorcraft distributor and what says is a motorcraft carb. All emissions are off/plugged. This is driving me crazy! The fuel lines are close to the header but I cant see a better way to route them. If its a vapor lock, why only do it at rest, not at speed? No hissing out of gas cap when released.

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post #2 of 9 Old 11-04-2010, 07:06 PM
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1972 CJ5 
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Location: Holland mi
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getting fuel, spark and compression whem it happens?
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post #3 of 9 Old 11-04-2010, 09:53 PM Thread Starter
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1979 CJ7 
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Location: Chattanooga
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definitely have spark and compression...i can hit the key immediately after it dies and it *almost starts again, sometimes does for just a second and then will not restart until it cools down. a buddy of mine says when it happens that he smells gas like its floded but if its idling, how does it flood?
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post #4 of 9 Old 11-04-2010, 10:21 PM
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1985 CJ7 
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i had a similar issue when i first got my jeep home, same exact thing, started up fine warmed up fine would run okay until it got hot and was sitting stationary, then it would start to sputter and eventually stall out. dont recall exactly where the line was that it was getting hot, but it was getting hot enough to cause vapor lock while idling and staying stationary but once i was on the move the air moving over the line was just enough to cool the line enough to overcome the vapor lock.
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post #5 of 9 Old 11-04-2010, 10:22 PM
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1979 CJ7 
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Do you have an electric fuel pump? I had one that would over heat but my motor would just suck fuel through untill i want to slow down and itt would quit. Then I have also been through the hole vapor locking thing and all you can do is try to keep the lines as far awayy from the headers as you can.
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post #6 of 9 Old 11-05-2010, 02:05 PM Thread Starter
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1979 CJ7 
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its a stock (but brand new) mechanical fuel pump. If anyone on this thread is running headers, is it better to run the fuel lines UNDER the header pipes instead of over top? This is one of those suituations where I really didnt pay attention (or take great pictures) when I was reinstalling the fuel lines to the pump. So aggravating!
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post #7 of 9 Old 11-05-2010, 02:22 PM
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1981 CJ8 
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not sure if this helps but I had the problem with it not starting back up until after it was cool. turned out my starter was getting too hot being right next to my headers. heat shield cured that.

I know you have additional issues but maybe they are two separate ones?

FYI.. my fuel lines are under the headers

'81 CJ8 Scrambler
'82 CJ8 Scrambler
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post #8 of 9 Old 07-25-2011, 09:29 AM
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1981 CJ7 
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I am having a very similar problem with my CJ7. Did you ever figure out what was causing your problem?
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post #9 of 9 Old 04-07-2013, 07:11 PM
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1978 CJ5 
Join Date: Dec 2012
Location: Englewood
Posts: 28
Welcome to the world of overheated Ignition Modules and Hall Effect Sensors

If everything else is new(er) and in good condition then your problem sounds like CLASSIC overheating of the ignition system.

Think about it kids, this guy's Jeep runs great on the highway but stalls out at lower and/or idle speeds and then refuses to restart for a long time --- this is because of two things:

#1: corrosion of the electrical connections inside your ignition components from many years of water condensation

#2: your ignition module and distributor (Hall Effect sensor actually) are at the end of their useful lifespan

----> spray a can of electric contact cleaner onto all the electrical connections & contact points and / or replace as necessary

or it could be vapor locking - CJ's tend to vapor lock sometimes with 10 to 15 minutes of run time usually because the engine gets really hot (thus boiling fuel in the lines and at filter above intake manifold) because CJ's are driven mostly at low speeds where less airflow goes through the radiator and over/around the engine & manifolds

------> replace your gas cap and consider insulating / wrapping your fuel lines in the engine bay area.

Last edited by denverdriveby; 11-24-2013 at 03:22 PM.
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cj7 , stalling at stop

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